CHAPTER VII--DRILLS, COUNTERSINKS, AND REAMERS

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP82-00039R000100240004-1
• Release Decision: RIPPUB
• Original Classification: R
• Document Page Count: 115
• Document Creation Date: December 22, 2016
• Document Release Date: March 20, 2012
• Sequence Number: 4
• Publication Date: March 19, 1952
• Content Type: REPORT

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STAT
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Chapter VII.
DTU_LJ , COUNTE1INKS AND BE il'ERS
DRILLS
Des nation and 7 eae
Drills are d.esi gned for (a) drilling holes in solid. mater:i a1;
(b) overs~.e drilling of already existing holes (as, for instance'
holes cast, forged, or drop-forged integrally); (c) the drilling
of tapered center holes.
(1)
04)
By design and purpose, drills are divided as follows:
spiral or twist drills; (2) center drills; (3) pointed drills;
straight-flute drills; (5) drills with hard alloy- tiPped blades;
(h) deep hole drills.
T~rist drills are basically representative' of this group
of tools, and they have found the widest application. They are
used for the drilling of: (a) holes that require no subsequent
machining; (b) holes .for subsequent countersinking; (c) holes for
subsequent reaming; (d) holes for subsequent threading with taps.
GOST 885 ? 241 cites the data recommended for use in the selection
of drill diameters in relation to the purpose of drilling.
wist Drills
Definition and ty e A twist drill (helical di-i l is more
correct) is a rod having two helical lips relieved at the point in
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STAT';'.
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(3) lef. tt hand straight shank for automatic machines (COST 2090
b3); () taper~sha.nk (COST 888 Li); (6) shortened with
accelerated taper shank (OST 20182 - ~O); (7) lengthened with
taper-shank (GUST 2092 m L3)3 (8) with tetrahedral tapering
shank for ratchet drills (OST 20231 - ~l1?
All the above enumerated types of twist drills are
differentiated by their shanks ,g the bits being basical-iy the
same in design conceptaana
Heavy duty twist drills, such as deep-hole drills, are
equipped w7 th special grooves to allow the flaw of coolant to
the cutting edgesm
For the machining of holes with two or three drill
diameters, two or thre'e~step drills are produced.
The basic terminology, desi.gnatiars, and definitions 'of
drills are summarized in G0 ST 289L. L>, and the geometric
parameters of the drill bats, in COST 2322 L3.
Parts anca structural contpone A drill consists of
the folloUr.'!.ng parts and structural components (Figure 1):
Fit, Parts and structural components of a twi.st drill.
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~.~ cu~;ting part [ t,hc chisel ed~~ei y y2 P
L .~- workings paxt, ~-
G
c ~, ~- shank 'length.; e ? tang;
alibrata.ng par t; l~ ..~ . neck .., ~ t_hand}
l .. ald.ing part; k helical flue (T'i~~litl~and or lef
e .. h '? o on
- margin; web; b cutting edge (tw
~. brata.ng edge (two on stray-ght
taper shank drills); c
~nk drills); a wW transverse edge (one at drill po. ),
sha
s back (relievers.) surfaces
~... Front surface ~
of a drill are? (a) the
The basic stxuctuTal elements
edge (b) the direction of the helical
cll~ set. ~ ,
_
~
[
FL ;awing
;
cutting par
flute ` (d.) the cutting edge angles,
~'1.ute; (c ) the shape of the
(e) the fax.rn of back (relieved) surface; (f) the back taper~
(g) the holding parts
i rocess of cutting,
The cut,tinF; par, li~ is bds if~ in the p
cutting companents of the dr111 m
Since it contains all the
acts as a guide in the process of
The ca1.~.brat~-ng part ac,
allowance for the reshaxpenir~g -'
cutting and is also the surplus
' mar ins are the cal ibrat~ing edgesg
oa the drill ? At a. is J.tip g
Which. determine the final formata.on of the drill hale
Fe 2), the double angle in plan
Angle 2 ~ (see g the
~SUred in plans has a great effect upon
t~h.e po~.n ~, angle men ,.
selected in re7.ati0n to the metal
It is
work Of the drill. It ~.~
machined, as indicated iii Table 1.
., angle and helical f ~.utc rake angle. .
Fib, Cutting edge
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Section ab
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TABLE 1
u.r......rM+nwn+~wwnwwrurrw.n+.w.~M~MYMw~.4eMOr.Nrouexv!1MltwlMWwYN'WA(O1MlI.A1id~11.HtaMdb~:Eiwl~A_Y_N.FWU:Vi.IM'MM%:;i~Y'1WNl'N,i:'~'Y,+^?~in}Hy
angle 'W (see Figure 2) is in close relation to the front
1e. 1Jith W increased., the front angle becomes increased,
ang
the cuttthg is facilitated, with a decrease in torque and
axial pressure, and an improved outflow of chip from the flutes.
However, with he increase in angle C) , he cutting edge of
the dri11 is weakened. This weakening, in the presence of the
same value for angle ~O , is relatively greater in the case
of small drills than in the case of large ones. Therefore,
small drills for universal use are designed with a smaller
a)
Steel, cast iron, hard bronzes 116 a 118
r
BraSSg SGf'~: brGnzema.oo.oasa.a..ra 130
Alumirtl~m, duralunin, silumin,
Material to be machined
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2'
in
degrees
1L0
r
Rea copper ....a.....?..a...a?.... l25
Ebonite, celluloida..a.??e..a a 85 90
Marble and other br~..tt1e materials 80
Direction of helical` flutes The helical flute rake
angle
electron, babbit..
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Values of angle 2
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Drills fabricated from high-speed steel work at an
accelerated cutting cycle as compared with drills oracle from
carbon steel or aloe steel, therefore, angle W is to be
of greater value for the former than for the latter. The
values of angle for drills in universal use are furnished
in Table 2
TABLE 2
Values of angle for drills in ianiversai use
Fnvp?10.~1o?',JmFnop~!~"~ ~Rl!I!!RJL?"M1~A7'?1 W Eq
,.;trNk~'tM11'NW.FM' 117nM+IM"'"tVM'1!aMtMPoN!MRWyA'~W?MrM!M~M~M2~PPC!A*NII.tN;NWSA.W~w;flIwrFfd.
' Drills from carbon steel
Drills from high ..speed steel.
Y 4 .. ihJ'Yrh'A',4'`{;eJfrn%?N'~Z. 'J.?.HY.t^! aaV, N~:;d~~ w%tb*d1~+'.i
G
a. ..
w+w~+.urwuM+nuwue~n~uamrT~trtxeFtF~mt^. t~R(dlMMw~ra~M~++w.a,N'"+%a?fM1UiulN.lw.a;NCt43t;4vK~f arntl
w
y
Drill diameters , W S' diameters ~~
millimeters in degrees in millimeters in degrees
in 4 r` p+'utri%
.
d,
t
'
!'p:Pn ~4t4Fwi+14*a7.1'W.?M1~;';V`6,6,
~yyArp;awvwneFSw~!lRa4+rt~YUi~31'riM~k7eR~+"'
I
1.145
1.55 ~ 3Q
3ml " L00
L.2 ' 6.0
6.2 8.2
8.3 11.5
ii.6 16.0
i6.5 - 22.0
22.5 _ 33.0
33.5 35.0
355 ..o
U.1.5 - 8
0
,.
a
,
M.t.~
WY ~ v:m+:akiF!3~FW'!RT.+O'r:t%CX'G.;~Y9".a'^,~'!tFFS%~",~(NtY'~5'a!v'r'~!AMPs~.q~,k..idiftGliroRn'x,~mt a4'~jSi~~r"i!4iJ.N~Y!Wh~r t
22 0.25 ? 1,0 19
~C
23 1.05 m l?5 20
232L. 1.55 3.0 2022
25 :i 6.? f. 22
26 6.8 to a 0 21~
10`.1 17.0 25
27
6
28 17.5 28.0 26
t
29 28.5 3900 ;? 27
iyl
d
r
30 39?5 ?80 28
31
T;
3132
32
33
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The selection of angle W` :1s made in re1atjon to the
type of material being machinedo This is of a 1-?
p r ,~.,,u1,ar im-
portance in the case of special drills. Angle CL)
(in degrees)
in special drills for the machining of brass
soft bronzes
ebonite, Bakelite, and celluloid is 8 - 12 degrees, for the
machining of marble and other brittle materials ~- 10 = l
degree,, for red copper and aiuminur,? ? 3 5 . 45 degrees, with
lower values for small drills and higher values for large
drills.
gist drills are usually made for right-hand cutting
with a right-hand direction of the flutes, Drills with a
lef t~hand direction of the flutes are used rarely, main/ for
work on automatic lathes.
5ha e of the flute The profile of th.e drill flute
must conform with. rigid specifications. It must provide for:
(a) strength of the drill; (b) rational dis tribu~;ior~
. of metal
t~roughout the section to prevent cracking in heat-treatment;
a
(c) ample space for chip dis ositian?
p , (d) t,he correct formation'.,
of chip upon the cutting edge and, its easy outflow from the
flute,
The basic components of the flute profile are the
thickness of the drill web, the width of the flute the for
of the cutting edge and the blending curves,
The diameter of the web do (see Figure 2) is selected,
in relation to the size of the drill. In order to attain
a
higher degree of strength, the web diameter for small
drills is
6
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made relatively greater than for large dri11s. For drillrelatively gzea~
a diameter of 0oc _ 1.2 millimeters, ...the web diameter e dual. s
(O28 + 0.20)D; for drills _th a diameter of 1oS M, 12 mina.
o w~
meters, the web diameter is (0a19 ~ 0415)D; for drills. with a
diameter of 13 80 ml i llirrieters, the web diameter is (Q.iL~ ?
0.125)D, where D ~. 's the drill diameter. Drills made from high'
ounof a high degree of decarbonization in
speed steel., on acc
the he a t tr eat men , must have their flutes ground. By the
the web diameter for high?epeed chills, of a
virtue of this,
to 18 ndilii..meters, before grinding, will be
d.iamc;ter D = 0.2~
er gre?.ter than the web diameter of carbon
0 03 M () 20 mi11 lme , t ti,
..
? For driLL sizes in excess of 18 millimeters no
steel drills
allowance for grinding is necessary
the drill, the web diameter is increased.
To strengthen
in the d:>rrection1 of the shanke %n the case of carbon steel
ax y1..1s, the th.ickeniz1; of the web equals l.~ millim.eters, and
f or high -sf>e ed dx ills , 1.75 millimeters per each 100 miilimeters
of lengths
e zdth of the flute is usually equal to the width
'~_
of the lip. For hhaspeE;d steel drills, it should be some-
what wider than the width of the lip (let us say, by 1/128
of the outside diameter of the drill).
The cutting edge of the drill may be rectilinear, Con
,ave. As yet, no preference has been established.
vex or concave, -
At present, all our domestic plants and first-rate firms
abroad fabricate drills with rectilinear cutting edgeso
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To avoid cracking in heat treatment and to facilitate
the chip outflow, the flute profile is to have well rounded
curves (see page 327 for the description of the profile-milling
cutters, with the aid of which this is accomplished)*
Drill angles. The cutting edge angles may be considered
as the grinding angles of the dr7_ll and also in the process of
cutting
Front rake angle is the angle between the plane
tangent to the front surface at the contemplated point of the
cutting edge, and a plane normal, at the same point, to the
surface of rotation of the cutting edge about the drill axis.
c 5c e 1 h /V
t/
'
[Drawl.ngl /
Fiore 3? Drill cutting edge angles.
[Drawin
Fure ~. Front rake angle at any point of cutting edge.
'i'o determine the front rake angle, it is necessary to
visualize the main intersecting plane, in which it is subject
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C . ~yz ~v ros~t4..
here C ; r) is the distance of the contemplated
R
point X from the drib. axis; R is the outside diameter of
drill; is the angle formed by radius rx with. the axis
of sylr~metry of the transverse section of the drill.
The thickness of the connector characterized by the
angle / insignificant effect upon the angle /{ exerts an Disregarding it, we may use the following approJ{amated formula
to cbange. Plane NN (see Figure 3), normal to cutting edge
( N)' is accepted as such a plane.
The front rake angle at any point X of the cutting
edge (see Figure 1 9 analyzed in the plane NN, is determined by
L~,
formula
to ?i, a)
SrrJ
It follows from the formula that the front rake angle s
which depends on the ratio between C = rx and angles
R
and
edge even for the same diameter of drill, sharpened to a definite
to
angle 9
The maXlmtlm (positive) value of angle 3.s at a point
is not uniform along the entire length of the cutting
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. Z2
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on the periphery ui
the drill, arid the minimum (negative)
value
is in the transverse cutting edge section ab (see Figure 2).
The sharply varying front rake angle is a considerable organic
defect in the design of the twist dr. i.lla
It causes the non-
uniform and rapid wear of the cutting edges At the periphery
of the drill, where the greatest cutting speed takes place,
the maximum amount of heat is liberated, and, due to the small
angle of taper, it cannot be eliminated rapidly, causing the
maximum wear to develop where the transition from taper to
cylinder occurs.
plane tangent to the back surface at the contemplated point
of the cutting edge and a plane which is tangent at the same
point to a surface generated by the rotation of the cutting
edge about the drill axis.
According to the prevailing standard. definitions, the
back angle, similarly to the front angle, is measured in the
plane NN (see Figur
3 ) normal to the cutting edge The main
plane of intersection for the back angle is plane 00, directed'
along the .drill axis arid tangent to the cylindrical surface
which is generated by the contprnplated point in the rotation
of the cutting edge about the drill axi..s.
The ratio between the values of angles and
in the planes NN and 00, for a paint at the drill periphery,
may be expressed by the approximated formula (disregarding the
.w
thicatness of the webs:
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The back relief angle O'- is the angle between a
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ta?2.. CYN -- Z72 _ CMG 5?/ii? 9
In order to attain a more or le ss uniform angle of taper
throughout the cutting edges and also to provide for the
adequate value of the back angle in the process of cutting,
it becomes necessary for the back relief angle to be variable
also. At the periphery, its value is accepted as 8 -JJ degrees,
at the web -- as 20 p 2 degrees, depending on the drill diameter
Sma:l.isize drills have greater values of the back relief angle
at the periphery than larger'-size drills0
Cutting edge angles in the process of cuttingo Taro
motions tike place in drilling: rotary (the cutting speed)
and forward (the feed). As a result of these motions, each
point of the cutting edge is shifted along a helical line at
a pitch equal to the value of the feed per one revolution. The.
helical surface generated in the process of cutting by the
cutting edge is the cutting surface, and the plane tangent to
it is the cutting plane. Figure `depicts the cross section
of the drill by a plane normal to the cutting edge and the
evolution of the helical line the trajectory of point A
per one revolution of the driliA
C Dr awi ng
Cutt.ng edge angles of drill in the process of
cutting.
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fez n t~N -fan as sin,
In order to attain a more or less uniform angle of taper
throughout the cutting edges and also to provide for the
adequate va7.ue of the back angle in the process of cutting,
it becomes necessary for the back relief angle to be variable
also.
At the periphery, its value is accepted as 8 - l- degrees,
at the web -- as 20 2 degrees, depending on the drill diarnetern
Smallsize drills have greater values of the back relief angle
at the periphery than lar. ger~size drillso
CUtfi,i.n ~ed angi.es in the process of cuttingo Two
motions take place in drilling rotary (the cutting speed)
and forward (the feed). As a result of these motions, each
point of the cutting edge is shifted along a helical line at
a pitch equal to the value of the, feed per one revolution. The
helical surface generated in the process of cutting by the
cutting edge is the cutting surface, and the plane tangent to
it is the cutting plane. Figure S depicts the cross section
of the drill by a plane normal to the cutting edge and the
evolution of the helical line the trajectory of point A
per one revolution of the drill.
C Drawing,
Cutting edge angles of drill in the process of
cutting.
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P :is the evolved length' of the circurnf erence 7Y D;
pw is the value of feed per one revolution; Ali is the cutting
trajectory (the evolved helical line generated by point A) ;
AN is tile normal to the cutting trajectory; Q , )2 are the
back relief and front rake angles, respectively, of the drill
bit; c'.r , y~r are t}ie respective cutting angles; & is
the angle of inclination of the cutting trajectory (the angle
between the actual trajectory of cutting and the conditional
tra jec Cory, .~bich is the circumference described by the rotation
of the dr:LU1.. without; the feeding motion)
The front cutting angle d?r is the angle between a
plane tangent to the front surface a t the contemplated point
o..1 ?t;he cut Li np; cclz~e, and a plane no:hmaa to the cutting edge
at; the sae point.
'1'k1e back cutt:u7g angle (fir. is the angle between a
plane tangent to the back surface at the contemplated point
of the cutting edge, and the cutting plane at the same point.
Both these angles are to be measured in the main plane
555
ot intersection.
The ratio between, , Gt and , J is expressed
as follows:
1 &;
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 Angle r; is determined by formula
S
d
In the presence of uniform feed. and reduce, value of
D, that is, with the points of the cutting edge moving away
from the drill periphery toward the drill web, angle & is
increased0 r1his is one of the reasons for the selection of a
variable back relief angle- m
Bank surface forma To provide for a variable back
relief angle, twist drills undergo special sharpening rIC
index for correct drill sharpening is the strict adherence to
the following requisite values: (1) of the drill bit angle
(2) oi' the transverse cutting edge angle ; (3) of
the back relief angle.. for points at the drill periphery
and at the drill web.
In, addition, the cutt ng edges, longitudinally, are '
to be of the same length and have equal angles , and the
drill axis is to pass through the center of the transverse
cutting edge [the chisel edge] . The non. observance of the
symmetry of the cutting edges will result in their non-uniform
(oneu?sided) loading and excessive free play of the drill,
which :in turn will result in a drill hole of excessive diameter.
The transverse cutting edge [ chisel edge] Wan;le Z
(see Figure 2) in properly 'sharpened drills is equal to L7
50 degrees for up to 12.mi1limeter drills and 52 S~ degrees
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for drills of l2~mi11imeter? diameter and above,
The slarpening of drills may be ~ done along the helical
or conical surfacer The most widespread drill sharpening
machines operate on the second principled Both these
tes
of drill sharpening; are presenter) diagrarnmaticall Figiue
6, which merits special attention, since it .represents the
drill sharpening done on machines of domestic makes as well
as machines irnported from abroado
[ Drag ng]
Fi uTe 6m Drill!.. sharpening; diagramed
he back relief angles are to be determined in relation
not only to the drill- diameter, but also to the type .
y pe of mah ,,.r~a,l
machined This is related to a definite setup in the dhil;l~
sharpening machines To set up the ~,?
p ~l-l sharpening machine
as per Figure 6, (a) it is necessary to
know the double angle
2 O for the conical surface, distance a from the cane
apex to the drill. axis, and (b), the value
o: f the displacement
of the cone axis from the drill axiso These values are in
r.elat:l.oi~ to the drill bit angle 2 : the chisel edge angle
and the back relief angle m The correl.atiansl~ips
between them are expressed by the following for~nula s
fad
n
( f 4) C9/(
x
zJ \d Jtr
/k'\2
CCs
) ()
lJ ~ b
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'-2 ac:)-
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O,
s(J)4*__
[c5(d) 1z]
4 = fan.(6t2P) -zMn..(~t~)T-~d~
dilere is the angle between radius rx of an arbitrarily
chosen point of the cutting edge and the axis of symmetry of
the drill (for a point lying in the web of the drill angle
,J' is transformed into ); 2 is the apex angle of
the generating cone; S W 90O , where 2 is the drill
bit angle; Q` is the back relief angle at an arbitrary point
of the cutting edge, which point lies on the cylinder surface
of radius rx. It is derived by evolving the cylinder surface
of radius rinto a flat surface,, as the angle between the
straight line of intersection of the cylinder with the drill
bit cone (2 C' ) and a line tangent to the intersection curve
of the same cylinder with the generating cone of sharpening
drill against the working surface and the liberation of heat
attendant upon it, the lip of the drill is depressed along
its entire length, with the exception of a small margin left
at the cutting edge. This margin is basically designed for
gliding the drill in the process of cutting. The width of the
margin is to be held to a minimum, otherwise excessive friction
will develop between the margin and the work surface. The
1s
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The margin. In order to reduce the friction of the
 t
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intermediate part (the angle) between the drill bit cone and
the calibrating part of the drill is under maximtui stress, dun
to the maximum cutting speed at the drill periphery and the
maximum liberatLon of heat then. ea The intermediate part, as
the weakest part of the drill, cannot provide for the proper
elimination of heat~ As a
small particles of the metal
being drilled become brazed onto the margin at the above men
ti.oned intermed:Late ang:te, causing thereby a further increase
in friction and in liberation of heat. This leads to the
rapid wear and d:Lsintegra-t,ion of the intermediate part of the
drill. The recommended values for the margin are given in
Table 3.
Drills having a diameter of 0.2S ? 0.5 millimeters are
made without a margin.
The margin values inci.cated in rr'able 3 are in effect
for originally fabricated drills. In milling, the width of
the margin is to be reduced, since it increases after grinding
along the diameter.
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o drillin. mm
a
M~
Y
I
-- J-- ;-....-.:.r_:ro w-..7:.sx.:.?r~?x.u.n,:arv.
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Mar in valies
F J z 1 5
b'
s
i
d
l-i
J
0.08 I X098 ~ o.lo ~ 0.10 ~ 0.15
t ? F
S
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Back taper. For smoother operation (reduction of friction
and heat), the drill. is made with a back taper in the calibrating
part, that is, the diameter of the drill bit at the shank is
smaller than the diameter at the cutting parts The value of the
taper per each 100 millimeters of length is to be within the
following range
Drill diameter
Taper
in mm
in min
1
~6
0,03 00()L
6
18
O s O5 .. 0.06
18
-80
0.07 0.10
In the case of straight-shank 12Mmiilimeter drills, the
back taper runs the full length of the drills
The reduction in the drill' diameter resulting from
subsequent resharpenings does not perceptibly affect the
size of the drill hole, since it is compensated by the free
play of the drill
In continuous operation, the drill may lose its back
taper on account of the excessive wear in the margin. This
occurs very frequently in low-alloy highspeed steel drills.
To avoid furthexwear and possible jamming, such drills are to
have their back taper restored.
The holding art ofthe ' shank. Drills are made either
with straight shank (diameter
shank (diameter ;- millimeters).
SDI 18 M
20 millimeters) or tapered
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 Declassified
S traigh t'shank drills up to 6 millimeters in diameter
may also be made on reverse centersa In order to avoid the
ti~.rning of the drill in the chuck or the drill holder in
highspeed operations, the straight shank has a flattened
rectangular end. to fit the driving slot.
Taper shank drills are made with a Morse taper. The
moment of torque being generated in the process of drilling is
to be relayed by the taper exclusively, without the participa-
tion or the tang, the purpose of which is only to force the
drill out from the tapered sleeve of the spindle. `fl e taper
shank (see Figure 7 ) must be designed so as to sustain the
full torque M, which is determined by formula
1-
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.p
Q pfd
F ('J'- :2 2 Li
where / 0.096 is the coefficient of friction occurring
between the surfaces of the sleeve and the tapered shank under
the effect of the axia:L force Q; 5'-" is one half of the apex
angle of the cone; D and d are the maximum and minimum diameters
of the working part of the shank taper.
The axial force Q may be resolved into P and V, it being
the case that force P induces on the surface of the drill body
a friction force P
The term enclosed in parentheses
accounts for.. the error in the angle of taped" (on condition
that the total error in the tapers of the sleeve and the shank
Li ( is not in excess of 10 minutes, i t may be accepted for
l
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 Declassified
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manufactured drills as
manut'es, that is, a total error of ? minutes
[Drawing]
lure 7. Forces acting upon the drill taper.
There is a constant ratio between M and Q in relation
to the material being rnachineda
M
C.oL.p) occurs in the case of soft steele Considering the
possibility of the occurrence of unfavorable circumstances
(accelerated deflections in angle
the drill, jamming of the chap, and the like), we may accept,
for purposes of computation, a three fold increase in the
value of the ratio M
Q
Substituting the values for M into the formula, the
rnaximum diameter of the drill, corresponding to each number
of Morse taper, can be determined.
It must be noted, that the maximum computed diameter of
drills does not coincide with the established standards. In
a coincidence of unfavorable circumstances, not only the taper
shank, but also the tang may participate in the relaying of the
torque. This is the usual cause for the breaking of the tang.
1tJith this in mind, the All?wUnion Committee on Standards pub -
lished an additional standard, GOS T 889 -~ 14 for drills with
accelerated taper to be used in Yeavyduty- operation.
2'minutes, for sleeves as ? 3
The most unfavorable ratio
, excessive blunting of
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Pro Tess in drill `des ;n. A twist drill ` of conventional
design is not a perfect. tool, Its substantia
l defect. is, first
of all, the sharp variation of the front rake angle
throughout
the entire length of the cutting edges Suggestions for the
improvement in the front rake angle design of the twist drill
are, at best, compromise proposals,
The maximum stressed (by work load sustained and heat
to be eliminated) area of the drill is its intermediate part
,
where the tapered. shape blends into the cylindra_cal shape.
This is the weakest area by reason of the excessive
value of
the front rake angle, To decrease the value of this angle
, a
special recess is made during the sharpening of the front
SU?face. The drill is rude with a greater angle of inclinatio.
n
and a helical flute of special design, as shown in leigLune 8
by the continuou line FPB1, in place of the usual flute
as
shown by the dotted line AFA1,
[ Drawing
'~ ure 8, Drill with recess made in the sharpening of the
front surface.
; Z 2e 2 -~.
E.
~a.:c a L
Variation in from; rake angle in the
pres
,, enc; c, of
special. recess in the front surfaced
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Special milling cutters are used in the fabrication of
such drills 0 For the equalization of the front angle, the
front surface at the drill periphery is additionally recessed
out in sharpening. Area BP (crossa-hatched surface in Figure 8)
is ground off until it coincides with the rectilinear area APo
The front rake angle remains constant from A to P, and only at
point P does it begin to decrease in a direction toward the
web? The variation in angle 1 (a) for the conventional
drill, and (b) for the drill with specially recessed front
surface, is presented graphically in Figure 9.
Some improvement, with relation to the wear of the drill,
may be obtained by removing the slight bevel in the front
surface along the cutting edge. 'he bevel usually varies in
width. At the periphery of the drill it is at its widest,
equalling half the feed value, and is gradually reduced to
zero in the direction of the web.
The increase in the front _rake `angle at th.e web is
obtained by recessing of the transverse edge and. its simuL.
taneous shortening. The transverse cutting edge, due to the
excessive cutting angle 9C~?
t ,.> ~ ~. 72 (see Figure 2),
works under heavy stress. It does not, cut, but scrapes the
material. It was es tablished experimentally that about 6~
percent of the force of feed and about l~ percent of the
torque is sustained by the transverse cutting edge [chisel
edged of the drill. With it recess-sharpenin1;, the axial
cutting force is decreased, and the process of c1ii.p formation
improved. The recess~sharpenjnr of the chisel edge is particu~
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l a:rly necessary in the case of worn-off drills,' the web of
which is considerably thickened toward the shank, and in the
case of large-size drills.
[Drawing]
Figure 1G. Recess-sharpening of the chie;el edge of drill.
The recommended recess-sharpening of the chisel edge
:is depicted in Figure 1.O To the left and to the right of the
chisel edge, metal is removed so that recesses are formed. These
recesses, in intersecting the back surface, form, in plan,
straight lines; which are a continuation of the cutting edge
from A to D. With this time of sharpening, the value of the
front rake angle in the chisel edge zone is increased, wi th the
chisel edge either foreshortened or left intact, as the case
may be. Recess-snarpenin.g does not weaken the chisel edge.
I. t is done after each regular sharpening of the drill, or,
at least, after two or three regular sharpenings. 'the length
of the chisel edge after recess-Sharpening, for drill sizes of
from l2 to 80 millimeters, is accepted within the range 15
7. millimeters, and the length of the recess-sharpening along
the drill., within the range 3 a l miliimeter s
The detrimental effect of the chisel edge may be elimi-
nated by cutting out a groove at the drill point perpendicular
to the direction of the cutting edges. The cutting out is done
by a grinding disk of a diameter not to exceed i.5 millimeters.
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 cutting speed, particularly when dr. i11in; in cast iron, it is
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in order to increase the durability of the drill and the
recornmended that the drill be sharpened to a double angle
( see Figure :Ll_ ) : the conventional sharpening to 2 9 = 116
118 degrees; and an additional sharpening to 2 w 70
7
degreesa nIhe width of the edge is made to be from Udi8 to U.22
of the drill d.iarneter~ The higher durability of the drill ob~
tairled. in this manner is clue to an improvement in chip formation
(a thinner and ender chip) and to an improved heat elimination.
Double sharpening i ~ reconinierid.ed for drills having a diameter
in excess of 10 w 12 miliimeterse For small size drills it
is not; effective.
[ Drawing]
Figlzre ii. Double-sharpening of drill.
To decrease the detrimental effect of to cylirdrica:L
margin, it is recommended that it be relieved at the cutting
part for a length l= 145 - L. millimeters, in the case of
l?_ - 80 m:i_l.l.ime:te.r. dril.l.s (see Figure 12)a The relievi.nL; of ` ~`~
,
the margin i.s d.orle to an angle (- = 6 B degrees, leaving
fal~t:
a slight bevel f within the range of 0.1 0.3 millimeters. G
Drawing]
Section AB
Fevre l2. 'lie relieving of the margin,..
2L.
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To cirt ec!,owri wear, the small intermediate angles where
the taper ends and the cylinder begins 'should be curved out in
the strip AB -- 5 - 6 millimeters long (see Figure 13). The
radius of this curvature, in relation to the diameter of the
drill, i s to be within the range C.~ ' 1.2 millimeters.
View along arrow C
[ Drawing]
I ___ . Rounding out the angles
in order to facilitate cutting, particularly in he 90 degrees, a pointed drill works
under more difficult cond .ti.ons' than a twist c?rill. To
render angle ~S more favorable, the front surface is re-
cessed so that` 0. When the recess is deep, the blade
is weakened, and the general strength of the drill is diminished.
The back relief angle is selected within the range of 10 - 20
degrees, it being the case that for drilling in ductile and
Section CT)
Pointed drill's.
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Drawing
St a vht-flute drills are used for the drilling of
holes in thin sheets of ductile metal, such as brass4 In
contradistinction to twist drills, the screwing in and jamming
effect of the drill in the hole is absent. Their cutting
elements' are selected in the same manner as for twist drills.
Their shortcoming consists in the fact that, like pointed
drills, their cutting angle is greater than 90 degrees, which
handicaps the work of the drill.
Drills with hard-alto roped blades. Due to the
physical properties of hard alloys, these drills have only
limited application. They are suitable for drilling in
materials that do not require high values for the front rake
angle, such as cast iron (particularly in 'the presence of
casting skint), hard steels, plastic masses, ebonite, bake
lice, glass, and the like, and also in those cases when the
feed values for hard alloy tools and high-speed steel tools
are fairly equal. In this case, the productivity of the
machine tool is increased due to the utilization of higher
cutting speeds, as, for example, in the machining of light
alloys, cast iron, etc., in high-speed machines. Due to the
low strength of the hard alloy-tipped blade and the necessary
presence of considerable cutting angles, it becomes necessary.
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to forego the utilization of hard alloys in the drilling of
ductile metals (such as steels with o < 100 kilograms per
square millimeter).
Drills with hardwai1ey~.tipped` blades are made in sizes
ranging from 3 to 0 millimeters, it being the case that in
small-size drills (up to 8 millimeters), in place of a com-
plete brazed-in blade, a cutting hard-alloy insert is butt.
brazed to the holder. The diameter of the holder is made
smaller by 0.3 - oa5 millimeter than the diameter of the inp
sect. Hard-.alloy~tipped drills must comply with rigid speci-
fications as to strength, reliability, simplicity of blade
bracing, and rigidity of the entire structure. The drill is
to resist well the cutting force and is not to show any
yielding during its work. The vibration in the drill is the
basic cause for the chipping of the blade. Due to the weak-
ness of the drill point and the drill web,' twist drills are
not very amenable to hard alloy tippling. To reinforce the
drill, it becomes necessary to enlarge the web and to thicken it'.
The length of the hard-alloy tipped drill bit is made
smaller as compared with conventional drills, since they can
be utilized only (resharpening stock) in a length equal to
that of the hard-alloy blade. The smaller length of the
drill bit results in a smaller degree of yield.ing during the
drilling operation.
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tins part of the drill holder, drills designed for the
machining of part-icu1ar1Y hard materials are made from
i:i
hardened high-speed steel. In other cases, the material
for the drill holder can be alloy- or high-carbon steelo
The design of the drill varies in relation to the
designation of the drill (type of material to be machined,
depth of drilling) e
In the drilling of ,hallow holes, the direction of
the flutes has no inportant bearing on the chip outflow.
The , flutes may even be straights For deep-hole drilling,
drills wLth helical flutes must be used. The angle of inclinap
Lion is selected in relation to the material machined,
being 10 - l~ degrees in the case of hard materials giving an
overflow chip (Figure 25, a) and 5~ - 60 degrees in the case
of brittle materials giving 'a spailing chip (r'ig?e 2~, b).
As can be seen rom Figure 2~, b, the calibrating part of the
f
drill ac t s as a screw conveyor for leading out the chip
format Angle 2 for the cutting pant of the drill,
~.ons e
materials giving an overflow chip, is selected
in the case of
at 12~ M 130 degrees, and, in the case of materials giving a
sppalling chip, at 116 - 118 degrees. To avoid weakening, the
front surface of the blade is sharpened to a small front rake
angle within the range of 0 - 3 degrees for materials
giving an overflow chip, and, within the range of 1~ p 7 degrees
for materials giving a palling chip. Table 6 cites the data
on the selection' of angles 27 and 7 in relation to various
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materials to be machines..
Blade
Blade
,iure 2 Drills with hard-alloy blades.
Cast iron HB = 200 .
HR = 300 X00
Steel castings, stainless steel, chromium
nickel steel O~ = l40 kilograms per square
lnillime ter . . . . . . . ? . . ? . ? ? . ? ?
ganese steel .. ?
Malleable iron
Phosphor bronze
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Material to be machined
in degrees
TABLE 6
Data for the selection of angles 2 and
for various materials
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The transverse cutting edge [the chisel edge. should
be sharpened. The back taper, for the length of the blade,
is selected within the range of 0.03 0.05 millimeters. To
facilitate the flow of the chip, the flute surfaces must be
well burnished.
drilling to a depth exceeding the diameter of the drill 5
or more times. There is contlnuous and radial drilling.
In the latter case, not all the metal is forraed. into chip
a bar remains in the center of the :blank. This bar is re-
moved, depending on its size, by breaking off or undercutting.
The machining is done in a boring lathe, usually, with rotating
work and forward motion of tool, and, less frequently, with
both rotating work and rotating tool. Specifications for
deep bole drilling are as follows. the drill-hole axis is
to run true to a straight line; the drill hole is to be
concentric in relation to the external surfaces; the drill
hole is: to run cylindrically true throughout its entire length;
the degree of finish and precision is to run within the range
of OST second and third class. Deep?hole drills run in size
within the range of 6 - 100 millimeters, and their various
designs are stipulated by the various sizes and specifications
of the work.
Ordnance drill. An ordnance drill is a cylindrical bar
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sheared off approximately to half its diameter (Figure 26).
To avoid jamming, the front surface is made higher than the
center by the value f = 0.2 + 0.5 millimeters, depending on
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the size of the drill. The main cutting edge is at a right
angle to the drill axis, and the auxiliary cutting edge is
sheared off at an angle of 10 degrees. At its beginning, it
is set off from the drill axis by 0?S millimeter. The drill
point is chamfered to a radius of 1 p 1?5 millimeters. Along
the entire length of the drill bit, a strip is sheared off at
an angle of. 30 '- L5 degrees. The back relief angle is equal
to 8 a 10 degrees The back taper is accepted within the
range of 0.03 Oa05 millimeters per 100 millimeters of
length. Sometimes the drill is made with a recess' in the
front surface (see section NN).
Section NN
drill resembles a boring cutter, and must, therefore, be
placed in a jig, or begin its work from a preliminarily rough
drilled hole in order to provide an adequate bearing surface,
The drill operates under difficult conditions due to the
large cutting angle (90 degrees), to the difficulties in the
egress of the chip and in the admission of coolant, Another
defect of the ordnance drill is the non--warranty of the true
geometric axis of the drill hole due to the drift of the drill a
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[ the bit], 60 i~O millimeters long, made from highspeed
steel, and the clamping part, made from carbon steel, the end
of which is inserted into a s:Leeve for .fitting into the chuck.
The bit is eauipped with a round or sickle-shaped hole (with
an angle of 130 - 11O degrees) for the admission to the cutting
edge of the coolant mixture (Figure 27). On its return, the
coolant liquid, together with the chip, flows out along the
flute. ? The flute angle plays an important part. Due
to the great drilling depth, the drill sustains longitudinal
bending and twisting, stresses, which necessitates a provision'
for the adequate rigidity of the holder, particularly when
drilling to small diameters. Angle ( also stipulates the
dimensions of the flutes, along which the feeding and the
leading-'oi1' of the coolant and the chip take place. With a
decrease in the value of angle 'J , the rigidity of the
holder and the velocity tension are increased, with the
attendant increase in the friction of the chip 2gainst the
flute surfaces and the danger of the chip becoming wedged
in the flute. It is recommended that angle ) be kept within
the range of 100 ~- 120 degrees.
Section AR Section CD
Figure 27. Rifle drill.
`The drill has one cutting edge, consisting of two
parts: external and internal.
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To guide the drill and to facilitate its penetration'.
d '
e ; about the drill
of the metal,' the drill point is displac '
axis by the distance b (see Figure 28) This displacement
"n forms a taper (see Figure'29, a), which acts as a bearing for
the drill, providing a guide in the cutting process. The value
of displacement b has a considerable effect upon the work
of the drill (upon its drift, its durability, the finish of
the machined.surface, and the like), and it is to be in relaw
tion'to the drill design and sharpening, and also to the
characteristics of the work material. Usually, b = a = O 25D
(drill diameter). It is, however' better to select the value
of b as smaller than the value of a (such as b = O.21J; a
Oe3U), and angle ) as less than angle (such as
~0 degrees and : 70 degrees). Under these conditions,
the calibrating edge, having a bevel f, will sustain a mini
mum of pressure, since the cutting .force component which is
perpendicular to the.drill axis will be of a greater value for
edge N :than for edge W (PN > P 1 in Figure 28)..
Declassified in Part - Sanitized
Axis of cone apex
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The calibrating` bevel cannot' penetrate the work metal,
and merely removes the combings. This prevents tl.iie drift of
the drill and the excessive widening of the drill hole, and
also increases its durability. A somewhat increased. pressure
toward the side opposite to bevel f is sustained by the
cylindrical surface of the drill body or by the solid guide
bevel0
To reduce friction, the drill bit is made with a back
taper within the range of OolO Oe3O millimeters per lO0
s
millimeters of running length in the case of S - 40 milli
I, , II r1
meter drillso To reduce the contact surface and increase the
effect of the coolant liquid, strips vdth narrow margins cut
out are provided. Margin f (see Figure 27) designated for
the trimming and the calibrating of the drill hole is to,
be within the range of O.I. - 0.6 mUimeter.lith excessive
~f
values of f, the drill has a tendency to jam.
The cylindrical bearing surface must lie opposite the
margin f. The remaining margins are guides, and their dimen-
sions are selected by considerations of design, with due note
takers of the width of the strips . he depth of the strips is
usually o0l~ - O.2~ millimeters, The flute apex is to be
below the center of the drill (by h O.OS = 0.18 millimeter),
otherwise it will not function, and may bend, or even break.
During the running of the drill, with the flute apex below
the drill center, a core is formed in the center of the drill
hole (see Figure 29, b). The diameter of this core is the
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Margin
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of this core easier, its diameter must not exceed 0.03 of the
drill 'hole' diameter. The front rake angle is to be kept within
the range of - 8 degrees, the back relief angle on edge N --
within the range of 8 10 degrees, the back relief angle on
edge W --within the range 12 a 20 degrees, the drill point angle
Their height, in relation to the value of feed per one revo-?
lution and to the ductility of the work metal, may be accepted
as 17s, where s is the value of feed in millimeters. The
chip breakers are to have undercuts at a 6 ?? 8 degree angle
to provide for the corrugated form of the chip and the
requisite direction of its egress.
Margin
Figure 30, Hardwallo J-tiPped rifle drill.
Hard-alloy
tip
Experience is available in the use of hard-alloy-tipped
rifle drills of a 7p~ 13 mi1li7heter diameter( see Figure 30).
A. hard''ai1oy adapter equipped wi th a flute f oz the chip ? flow
and an angular catch is brazed with its face to a short carbonM
steel holder, which, in turn, is brazed onto the basic tube.
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Sharpening is effected with the aid 'of a diamond grinding disk
mounted on a conventional drill-sharpening machined The
geometric parameters of this drill bit' are presented in Figure
F _ e_ 31. Deep hole drill.
F. Drawings]
A substantial defect of rifle drills is the presence
of only one cutting edge, a circumstance which reduces its
productivity. A conventional twist drill with flutes for
admitt1ing coolant, although equipped with two cutting edges,
does not provide for high productivity, since the drill, from
time to time, must be removed from the drill hole for the
removal of the accumulated chip. Figure 31 shows the con-
struction of a deep-hole twist drill. In the place of twos
it has four margins, which form the channels for the admission
of coolant. The shank has a drilled hole communicating with
the hole at the end of the helical flutes which is perpendicular
Although this drill has high productivity, it does not
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provide .1'or a good surface finish and is not free from drift.
The drift is caused by the improper sharpening of the multi-
blade drill and by the presence of the chisel edger The
detrimental effect of the latter may be reduced or even corn-
pletely eliminated by the following: (l) the drilling out
(in the drill) of - a longitudinal hole, the diameter of which
is to be greater than the chisel edge diameter (such a drill
see Figure 32, a ? has an internal flow-off of the chip and,.
in drilling, will form a core); (2) the drilling; out of a
blind center hole, hidden in one of the helical flutes, with
a ledge for the breaking off of the forming core, which is
removed through the hole in an outward direction (Figure 32, b);
(3) the substitution- of one cutting edge by two cutting edges
that really cut into the work metal and do not merely crush
it (Figure 32, c).
Large-diameter holes, on the order of 75 millimeters.
and 'above, are drilled by the method of radial drilling, with
the leaving of a central core of considerable diameter.. Radial
drilling is effected by a single-blade drill, or, more fre-
quently, by a multi-blade type drill head. The head consists
of a frame with clamped-in cutters, the number of which is
selected in relation to the requisite diameter of the hole.
Figure .33 shown the drill head face. Three cutters (2),
wedge-braced t.), machine the metal from two sides (diameters
D and d). Between' the central core and the drill head frame
(1) there is a gap of
6 millimeters for the admission of
coolant.. For the outflow of coolant with the chip, gap B is
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 Declassified in Part - Sanitized Copy Approved for Release 2012/03/20 : CIA-RDP82-00039R000100240004-1
Veremeychuk,' I. Sm , 'Radial .Drilling, Mashinostroitel'
(Machine Builder), no 12, 19t~O.
Nemirovskiy, AQ
so, nCom.puta'tion of Back Relief Angles
of Drill", Trull stanko.instrumental' nova
Tool Institute), volume VI, Publication
S tankin, 19Li.O.
Suvorov, A. I., "Deep.-Hole Drilling' Mashinostroitelt
(Machine' Build.er ), No 12, 'l9Li.0
COUNTERSINKS
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provided 'between the hole/ drilled out and the drill head frame.
The 'drill head is equipped with metal or wood guide cams (3).
Designation and. ypes
Countersinks are intended for
(a) enlarging cylindrical holes previously obtained by
cold or hot treatment;
BIBLIOGRAPHY AND SOURCES
. Aref'yev, M. G., and Ka.rpov, L. I., Profuction of Rifle
Barrels, Oborongiz, 19L;.
 Declassified in Part - Sanitized Copy Approved for Release 2012/03/20 : CIA-RDP82-00039R000100240004-1
(b) machining cylindrical recesses for screwheads or
necks 'of screws, etc.;
(c) machining conical recesses for center holes under
screwheads, for valve seats, and the lake;
(d) trimming of face surfaces.
For the first, group of operations, the following types
of countersinks are usede (l) taper-shank (CeOST V 1676
2 inserted-blade (OST 'NK1 3677) with arbors; (OST NKTP 3678
(3) sectional- adjustable inserted blade (GOST 2255
For the second group of operations, the. following
types of countersinks are used.: (1) with pin for enlarging
cylindrical screwhead holes; (2) with pin for enlarging holes
for screw necks.
For the ttird group of operations, countersinks known
;ij
as countersinlt reamers are used (1) 60 degree included' angle
plain centering (OST 3728); (2) 60 degree included angle for
center holes without a safety cone (OST 3729 combined with
OS T 3730); (3) 60 degree included angle for centering with
taper shank (OST 3731) ; (G) countersink reamers with various
other included angle values (7 degrees, 90 degrees, etc.) for
various opera tions
For the fourth group of operations, spot-facing counter-
sinks are used (1) with shank; (2) inserted blade, one-side
and two~sid~, solid and sectional.
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eS and the geometz^y of cQUn~ersinks.
Designate-oils,
Countersinks for enlarging holes are used for holes to be
'
finished to thefourth to fifth classes of precision and for
holes to be reamed to the second to third classes of precision.
The external diameter. of the countersink is selected to con
' th the requisite stock allowance- for
;, w s-
farm with the above -
reaming taken into account.
A countersank consists of the following parts an
'
l ~ the bit; 11 -the cutting
~-guxe 3
design elements (Figure 3L) , ~
par?b; 12 ? the librating part; 13 the neck; i - the
ca
. d .. the arbor fitting hole; k the flute
shank; e a the ?tang,
'th ri ht?hand or left-hand direction);
(straight or helical, wi g
p the lip; f a the margin.
The basic elemenis of design are: (a) the cutting
~. , the d~.rectlon of the flute, (c) the blade angles;
pare (b)>
d the margin; (e`) the back taper.
F?gur ? Counter Sirlk parts and elements of designs
~.
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Drawing]
, where t is the thickness 'of the chip; is the
Figure 36. Geometric elements of countersink,
C Drawings]
Figure 37. Angle of inclination of the cutting edge? of
countersink.
In the technological process of machining the hole,
the countersink occupies an intermediate place between the
drill and the reamer; The design of it is stipulated by
this fact. The countersink resembles a drill, but has a
greater number of lips, which provides for better guiding and
a higher degree of finish in the machined surface.
In contradistinction to a reamer, the countersi
:. cuts
by means of facing teeth, namely, by the face cutting edge
m and the margin edge n (see Figure 35). The value of
t
cutting part angle. The value n -? ,where so is the
z
value of feed per one revolution and z is the number of lipso
The geometry of the countersink tooth is depicted in
Figure 36`; the front surface (l), along which' the chip is ejected;
the back surfaces ..,, axe.
main (2) facing the work surface, ' auxi-
liary (3 ) a which is the cylindrical surface of the margin,
touching the work surface; the main cutting edge (Li.), formed
.. 5 ' n
' r~W ~'^~;t' i4l rAnS .ii 1kY fp&~ ~Y ~p~~f~ ~p ' ` ll
Declassified in
/.
[Drawing]
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Margin on tapered
part
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by the intersection of the front and main back surf aces, and
performing the basic work of cutting; the auxiliary cutting
edge (S), formed by the intersection of the front surface
and the auxiliary back surface (the margin)', blade point '(6),
which is the point of intersection of the main and auxiliary
cutting edges.
To determine the cutting angles, it is necessary to
know the coordinating planes ~- the basic plane and the cutting
plane.
The basic plane passes through the given point of the
main cutting edge and the countersink axis perpendicular to
its face.
The cutting plane passes through the given point of
the main cutting edge tangent to the surface of cutting.
In analyzing the cutting angles in a static position, the
cylindrical surface generated. by the rotation of the given
point of the cutting edge (without feed) is considered as
the surface of cuttingo
The angles in plan (main and auxiliary ) are
1
included between the direction of feed and the corresponding
projection of the main or auxiliary cutting edge, respectively,
upon the basic plane (see Figure 35).
The `cutting edge angle of inclination ,4. is included
between the main cutting edge and the basic plane. It is
measured in a plane passing through the given point of the
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cutting edge normal to the basic plane. By analogy with a
cutter, the cutting edge of the countersink may be designed in
three variants (see Figure 37) When the point of the tooth
,
is below the remaining pain~, y Cs of the cutting edges angle 2.
is positive (> U), when it is above, angle ~. is nega
tive ( < 0), when it is at the same height,
is formed by a plane tangent
The .:front rake angl:,
to the front surface at the given point of the cutting edges
and a plane normal to the cutting plane, drawn through the
..
same point
The back relief angle O- is formed by a plane tangent
to the back surface at the given point of the cutting edge,
and the cutting plane passing through the same point.
To complete the determinadan, it is necessary to
establish the coordinating plane. The front rake angle
and the back rely ?.ef` angle O- of the countersink are usually
:
specified, by analogy with UST 6698 ("Basic concepts in
machining r , with cutters") 'in the main section plane normal
to the projection of the cutting edge upon the basic plane
( see Figure 38)a The back relief angle can also be measured
in a plane tangent to the surface of motion.
Section KK
Direction
Fi ure 38! Cutting edge angles measured in various planes.
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00240004-1
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When designing and fabricating countersinks, it is
necessary, by analogy with cutters, to operate with front
rake and back relief angles measured in planes: (l) KK --
normal to the direction of feed ( ' J ); (2) LL - para~
llel to the direction of feed, tangent at the given point to
the cylindrical surface generated by the rotation (without
feed) of this point
cutting edge ( cZr,
( ?-z'??2) (3) RR
7t)a
normal to the
The relationships between the front rake and back
relief angles as measured in various planes are
tan ? tan, ?
?
tan Yz = tan Z/
tan Zi;/ = tan ?
tan v2' =tan ' ?
r (N.
cos M tars Z ? sin
s
sin + tan , ? cos ' ;
cos 92 + tan ' sin' ;
cos
2;
cot al = cot , cos Z' . tan , ? sin
cot tX == cot, cx? sire + tan 2 cos
cot' cot ~j ? cos 9 + 'cot ? sin'
cot w cot ~ /V ? C05 2 .
When operating with formulas containing ,. , it is
necessary to adhere to the rule of signs for the tangents.
Angle / is determined by formulas:
tan 2 = tan 2` ? cos I tan sin
tan 2 = cot cos - cot . . sin
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For the determination of / -/ in the ?ace section,
there is the formula
tan
tan 2
sin,
The cutting part angle exerts a considerable effect
on the form and the ejection of the chip, and is selected on
the basis of experimental, data. A properly designed angle C
is conducive to the proper ejection of the chip as conformant
with the direction of the flute. This is of particular `im~
portance in the case of metals that give an overflow chip. In
machining steel, angle 9 is taken as 60 degrees. To increase
tool durability in the machining of steely the cutting edge
is to be additionally sharpened at angle ) = 30 degrees, along
a :Length equal to three times the value of the machining stock
the side. For machining in cast iron, angle 9 is taken
as 60 or )4 degrees without additional sharpening In the
case of hard-alloy-tipped countersinks, angle 2 is some-
times increased to 7degrees.
Like a twist drill, a countersank is equipped with a
helical flute. To form a positive front rake angle, the
direction of the flute must coincide with the direction of
cutting. In plane LL, the front rake angle , for a
point on the periphery, equals the angle of inclination ( CD )
of the helical flute. Angle ) , which is linked with the
front rake angle, is selected in relation to the work material
61
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and, the countersink diameter. As the hardness of the work`
material is increased and the diameter of the countersink
reduced (for the strengthening of the cutting edge), angle
C?) is decreased. In countersinks for universal use, it
is accepted. within the range of 10 25 degrees.
bracing of the blades in sectional- countersinks, it is some-
force' and torque are diminished. The angle is se:Lec ted in
relation to the work mater, ibility in the place of -maximum stress. _ This is of particular
V't
importance in the case of hard-alloy-tipped tools characterized
+4 N I
rt
by higher brittleness.
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the case of a new countersink, the value of is to be so
selected that, following all the permissible resharpenings
it will still remain greater than or equal to zero. Angle
in the new countersink is also to be in relation to the
working height of the blade, and, generally, it is to fall
within the range of l2 16 degrees
There are various designs of sectional countersinks.
The most successful design is the one in which the bracing
of to blades is accomplished by way of riffled construction
(see Figure 1~?a
Section ABGD
[Drawing] [ .Drawing]
Section ABCD
[Drawing] [Drawing]
[Drawing] [Drawing]
[Drawing] [Drawing
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 I
Declassified
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Let us analyze these riffled constructions. The
countersink represented in Figure L.2, a,consists of a body
(1) with grooves inclined about the tool axis and with wedge-
shaped knives (2 ) with a p degree radial inclination angle.
The body grooves and the blades are riffled so as to permit
the adjusting of the diameter after blunting by shafting over
one or several rifle graduations. The wedgelike shape of
the blades provides for their reliable bracing in the body
of the tools The defect of this design is that there is no
axial hlade adjustment.
Figure 42, b, shows a modified design. The blade
(2) and the body groove (1) have transversely running riffles
and a double inclination, degrees in a radis.1 direction and
1 degree 30 minutes in an axial direction. The countersink
is provided with double control, radial and axial. The defect
in this design is that the transverse` direction of the riffles
does not allow the use of the broaching method in the machining
of the body grooves,' requiring instead the laborious operation
of slotting.
Figure L2, C, shows a design consisting of a body (1)
with wedge-shaped grooves inclined about the tool axis, wedges
(2), and blades (3). The lateral side of the groove and the
adjacent side of the blade have longitudinal riffles, while
the other side of the blade and side of the wedge adjacent to
the latter have transverse riffles. This design provides for
double blade adjustment, axial and radial. The defects in this
68 .~
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design are the ciosed-_n groove, which makes it impossible to
use the method of broaching in the machining of the riffles,
and the projection in the blade for the transverse riffle.
. In the design shown in Figure L2, d, the blades (3)
and wedges (2) are riffled longitudinally. Wedge (2), with
a radial inclination of degrees, braces blade (3) in the
body (1) by the method of tight fit. The design provides
for double blade adjustment (axial and radial). The defect
in the design is to complexity of machining the grooves for.
the tight fit.
re countersink in Figure 2Li, e 'shows an improved
design as compared to the preceding one. Blades (3) and
wedges (2) are longitudinally riffled. The grooves in the
body (1) have a s-degree radial inclination and a 3~degree
longitudinal inclination. Double blade regulation is provided
for
?seC ti0nal countersinks are to satisfy the following
specifications: (1) strength, reliability and rigidity in
the bracing of blades in the body; (2) simplicity in fabrica-
tion and the provision for adjustability of blades following
reaz^; (3) provision for a normal sharpening allowance along
the diameter following adjustment; (Li.) the more or less perma-
nent overhang of the blade with relation to the face of the
tool in resharpenings (see dimension k in Figure L3).
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Drawing
Figure 430 The limit values of countersink wear (amount of
stock removed by cumulative sharpenings)o
In the process of machining, the countersink blade
wears at the corner, or the transition area, formed by the
intersection of the back surface of the cutting part and the
cylindrical surface of the margin (the cross-hatched triangle
with length ;A in Figure 43
The
countersink wear, when
working in cast iron, runs approximately at the angle
Based on this, it may be recommended that the sharpening be
done to an additional angle
along a length of
bevel determined by 0.8 ? 102 millimeters.
In order to restore the cutting capacity of the counter
sink, it is necessary to grind, off the blade along the back
surface by Talue h, the diameter of the countersink remaining
the same. in sharpening, the extent of overhang of the blade
(dimension k) with relation to the face, is reduced. This
would lead to inadequacies in the work of the countersink.
Therefore, the feature of the bracing of the blade should be
so designed as to provide for the possibility of retaining this
dimension more or less unchanged.
There are limit values to the amount of stock that can
be removed along the axis M and along the height M1 of sectional
countersinks by resharpening s. ` Grinding off of stock beyond'
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those limit values does not any longe insure the requisite`
strength and reliability in the bracing of the blades, The
following sharpening stock values were established
empiricall.y.
where L is the length of the knife; m is the length of the
angular edge, a is the depth of the recess in the front
face, and s is the pitch of the riffle,
The 'best' indexes 'pertaining to ` the minimum allowance
for grinding and the maximum permissible number' of ..
resharpen
ings are given in the layout shown in Figure L2, d, which
has been authorized. as standard by GOST 2253 Sectional. countersin]s with a diameter from LO to
75 millimeters are made with taper shanks. Inserted blade
COUflter's:inks are made in diameters LtO to 100 mill
imeters.
The number of teeth in countersinks with a
diame der of up
to 55 millimeters is standardized as 1 a
-~, nd in those s
e with
a diameter of above 55 millimeters, as 6.
Figure 44 shows the elements of standard bracing b
g by
the method of riffling (GUST 2568 a LU ) , The riffle angle
is 90 degrees and the riffle pitch is 0,75 1,0 millimete
r9
The apexes are sheared off to form a little
platform: of 0,1 M
0.2 millvneter; the riffle notches form li
t t1e platforms
0.0$ 0,1 millimeters wide. The riffle thickness equals
the thickness of the notch along the center line of the profile,
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 Declassified in Part - Sanitized Copy Approved for Release 2012/03/20 : CIA-RDP82-00039R000100240004-1
The cutting elements of sectional countersinks are
determined by taking into account the work material and the
countersink blade material, and also the characteristics of
the countersink designo
[Drawing]
~,igur:4? Standard riffling for inserted blades.
Bracing'the countersink. Countersinks of standard
design, from 10 to 36 millimeters in diameter, are made with
taper shanks, and countersinks with a diameter of 25 milli
meters and above are `made with holes for `setting into arbors.
The arbors are also made with taper shanks. Shanks with
Morse tapers provide for the excellent centering of the tool,
resulting in diminished vibration and improved quality of
the work surface.
As airecult of operating wear and the removal of
stock by subsequent resharpenings, only a relatively small
section of the cylindrical part of the countersink sustains
a reduction in length. In order to increase the number of
possible resharpenings, it is recommended, in the case of end
countersinks, that a hole be drilled in the face of the tool,
and, in the case of inserted blade countersinks,,the length
of the, front part of the tapered hole (up to the internal
charnf er) be increased by ~0' percent, as compared to the length
specified for standard countersinks. Such a construction ,pro-
vides for the reliable bracing of the countersink in the arbor,
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regardless. of the many resharpenings.
In countersinks of standard design, there is no comp
plete utilization ,of the material constituting the cylindrical
part. To eliminate this defect, sectional countersinks with
removable heads .are used. The removable head is set into a
hardened carbon steel, or alloy steel body, which has the form.
of a conventional countersink with tapered shank, The removable
head, which is the cutting part of the countersink, is either
solid high-speed steel or is equipped with brazed?on hard alloy
t blades, Countersinks of such design are very effective in
machining with control guides (for instance in aggregate machine
tools) and also in the machining of deep holes. The long body
of the countersink provides excellent guidance in the work.
The junction of the cutting head with the body is effected
by several methods.
In the design shown in Figure 145, a, the head is equipped
with a 'square extension, for which. a square hole is provided in
the body of the countersink, with a through groove provided in
the body to facilitate the ejection of the head, The head is
stayed with the aid of a bolt passing through its entire length
(Figure L5, b)o
{Drawings]
Section AB
(b)
Figure J45. Countersink shaft with square hole for head,
73
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 Declassified in Part - Sanitized Copy Approved for Release 2012/03/20
regardless of the many resharpenings.
CIA-R D P82-00039 R000100240004-1
In countersinks of standard design, there is no con'
plete utilization of the material constituting the cylindrical
part. To eliminate this defect,' sectional countersinks with
removable heads are used. The removable head is set into a
hardened carbon steel or alloy steel body, which has the form
of a conventional countersink with tapered shank, The removable
head, which is the cutting part of the countersink, is either
solid high-speed steel or is equipped with brazed-on hard alloy
blades. Countersinks of such design are very effective in
machining with control guides (for instance in aggregate machine
tools) and also in the machining of deep holes. The long body.
of the countersink provides excellent guidance in the work.
The junction of the cutting head with the body is effected
by several methods,
n the design shown in Figure L5, a, the head is equipped
with a square extension, for which a square hole is provided in
the body of the countersink, with a 'through groove! provided in
the body to facilitate the ejection. of the head. The head is
stayed with the aid of a bolt passing through its entire length
(Figure L, b)0
[Drawing S j
Section' AB
(b)
Figure i:5 Countersink shaft with square hole for head.
73-
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Drawings
G Drawings)
[Drawings]
Section AB Section CD
Figure l.6. Countersink shaft with hexagonal hole for head,
Section AB
Section AB
Section ABCD
Figure 1i8. Countersink shaft with sheared tang (a) and with
rectangular groove and securing screw (b).
in place of the square, which simplifies the design. The stay
bolt is screwed into a hexagonal nut, which, in turn, is in-
serted into the hexagonal hole in the countersink body. The
nut is prevented from falling out by a spring in the form of
an unlocked ring
:
into the corresponding internal champ
fer of the hole. To facilitate ejection, the hole is made to
run` through.
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Bracing, as depicted in Figure L8, is effected by two
alternate methods: (1) by the tang of the shank inserted into
it
the corresponding recess (Figure L~8, a); (2) with the aid of'
the tang of the shank, the rectangular groove at the greater
diameter of taper, and the securing screw (Figure 48, b).
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The bracing shown in Figure L.7 consists of a dowel pin,
inserted into the holes drilled in the countersink body and
the countersink head. To facilitate the ejection of the head, a
spring, braced against the internal face of the head taper, is
provided.
Sectional countersinks are also used for the machining
of shallow holes. One such design is depicted' in Figure X90
The body is Morse-tapered, while the countersink head has a
straight shank with two projecting cams in the center for
bayonet bracing. The head, compressing the spring, is in-
serted into the body and turned in a direction opposite to
the tool rotation. The cams fall into the corresponding in-
ternal chamfers of the body and effect the transmission of
torqued This countersink design is rather complex in fabric
cation.
[Drawings]
Figure 1t9. Shaft with bayonet bracing.
75
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Relieved -.-.-..--
surface
;
Section EE
Figure 52, Double-thrust countersink with large surplus stock,
Figure 50 depicts the bracing of straight-shank counter-
sinks in quick-change chucksm This design is authorized as
an All-Union standard (COST 3009 - L). The shank has an
annular groove' (1), flan' surface (2), indicated by dimension ii,
[ Drawing
[Drawings]
Position
Drawing] [Drawing]
Section BB Section DD
Section AA
 Declassified in Part - Sanitized Copy Approved for Release 2012/03/20 : CIA-RDP82-00039R000100240004-1
and radial groove (3)' having a width (b) - bowel pin (i )
is pressed into the body of the chuck, and a locator device,
consisting of dowel (5) and annular spring (6) is provided.
The countersink shaft is inserted into the chuck, in position
10 The flat surface (2) passes freely under dowel
(L).; Dowel
(5) under the action of spring (6) is flipped into pped xntothe annular
groove (1), fixating thereby the proper location of
the tool,
When the machine spindle with the chuck mounted on i
t rotatesi
dowel ()4) enters groove
3),
working motion of the countersunk (position II) a The locator
device prevents the countersink from falling out and renders
effective the rapid and convenient bracing of the s
g hank in the
chuck, At each turn of the machine spindle, the chuck dowel,
entering the groove, by itself grips and guides the counter
sink. This arrangement is particularly important in the case
of vertical spindle machines In actual operations, both a
dowel locator device (Figure 51,` a) and a ball locator device
(Figure 51, b) are used.
Shanks of the above described type (for 10 ~. 5o milli-
meter countersinks) successfully replace the Morse
gaper type
of bracingo The advantages are manifested in the simplifica~
tion and rapidity of mounting and dismounting the tool, and
also in a saving in material, since the shank assembi,~ of
y
this type is 2 ? 3 times shorter than a Morse taper shank.
The defect of such bracing is that the straight
shank, as comp
pared to the taper shank, does not provide for better too cen?
tering nor for a; higher degree
77
grips the shank, and effects the
of surface finish. It can,
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00
11
 Declassified in Part - Sanitized Copy Approved for Release 2012/03/20 : CIA-RDP82-00039R000100240004-1
therefore, be recommended for work of lesser precision.
The double-thrust countersink depicted in Figure 52, is
braced in the arbor with the aid of two torque-transmitting
dowels and a center hole. The countersink is used for the
machining of through, blind, step, and profile holes, having
a diameter of from 30 to 200 millimeters and a length up to
Li000 millimeterso When machining in continuous material, it
is frequently used in combination with a drill mounted on the
arbor ahead of the countersink. The countersink is capable
of removing considerable machining stock allowances, has
greater productivity and durability, and permits a consider.-
able number of resharpenings.
The back surface of the main cutting edge, which is
relieved, non-ground, with chip breaking annular grooves,
has a 60 or i~ degree angle in plan. The calibrating part
S cylinder-ground, or ground to a small bark relief angle
(30t ,.'2? 3O). sharpening is done only alung the front
surface. In contradistinction to the conventional counter
sifk a double thrust countersink has a short bit without
wide margins, which prevents the wedging of the chip and
g _
its adherence to the tools The front rake angle is selected
in relation to the work material within the range 10 - 2,
degrees; the back relief angle is 8 degrees. For purposes
of proper ejection of the chip, the cutting edge has an angle
of inclination
degrees.
78
? 10
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~auntersinks for Cylindrieal Holes.
To machine holes to fit cylindrical heads (Figure 3, a)
or screw necks (Figure ~3, b), 'countersinks are used. These'
`
not differ from each other, with the exception
countersinks do
of the sizes of diameters and pivot journals. In small sizes,
~.
they are made with straight shanks, and in large sizes, with
taper shanks. At times they are made in the inserted blade
characteristic of this type of countersink
formti A special
is the presence of a pivot journal at the face of the bit.
'
serves to guide the countersink in'operation
The pivot journal
and to provide for co-axiality of the countersink hole to flat
the screw head and the hole to fit the screw stem. The pivot
journal is made either integral with the countersink body or
is replaceable. The last type is preferable, since it permits
more resharpenngs, facilitates the process of sharpening, and
~.
utilization of. the countersink fora group of
permits the
diameters by shifting from one size of journal to another.
...
Figure 3. Form of cylindrical holes.
CDrawing] [Drawing]
(a) (b)
79
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Taper 1:50
Section AA
F e51~0 Bracing replaceable pivot journal to countersink.
Morse taper No 1
Section AB Section 0D
. Figure 5L depicts the bracing of 'the pivotjournal
to the countersink with the aid of a 'tapered section. There
are other methods of bracing the journal to the countersink,
as shown in Figure Li5 in the preceding text. The shaping
of the countersink bit, in this case, is depicted in Figure
55. The angle of inclination of the helical flute C.L) is
10 15 degrees; the undercut at the face is 8 - 10 degrees;
the back relief angle at the calibrating part _ 8
degrees; with lip 1 -' 1
0.2 millimeters. The lip has an additional taper at an angle
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O.i: 25 - 30 degrees. The angle of inclination of the
cutting edge ,L 10 degrees.
For the machining of center holes, the following types
f,f
of countersink reamers are used: plain, single-tooth (Figure
56, a), conical twist (Figure 56, b), centering (Figure 56, c), ;`'Sad
centering with safety cone (Figure 6, d). In machining centerp #` k
ing holes, the most frequently used angles 2 are 60-degree`
,y angles, and less frequently 75 and 90 degrees. For the machining
of conical holes, conical countersink, reamers are also used
(Figure 57). They are fabricated with an angle 2 9 - 60, 75,
90, and 120 degrees, and with a diameter from 12 to 60 milli-
meters. The number of teeth is selected, respectively, from
6 to 120. To facilitate the process of cutting, it is recomp
mended to shear off, with skipping of one tooth, a little
section of length 1 1.5 .5 millimeters. The web thick-
ness at face is selected, equal to 001D, and the diameter of
sheared face d ;^ (o.15 t 0.18)1J, where D is the diameter
of the countersink reamer. The angle of the recess Z is
in relation to the number of teeth and the angle of the tooth
body , which is determined by formula
where:
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 [Drawn
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no less than 30 ~0 degrees, Upon computations angle
..
is rounded out to fall in line with the conventional series
of angles of angular i1ling cutters. In order to maintain the
m
rm along the entire length of the tooth'
width of hp p _ un~.f o
it is necessary to compute angle ~ of, the dividing ..head setting,
r
which is determined by formula
is the apex angle of the countersink reamer cone;
where 2
360? . 1a. is the recess angle. The width of lip p
is selected within the range 0.0~ - 0.06 millimeters. The
back relief angle = 6 ., 8 degrees. `rhe front surface is
directed along the radius. The countersink reamers are made
either with taper spank or with shank as per Figure O.
...
[Drawing]
Section AB
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'Section AB
Face~Tximming Co~~rsinks
The peculiar characteristic off' these countersinks
an the face only. Countersinks of
is the presence of teeth
made with hellcat teeth on the stem...
this type are rarel;Y
The design is insertedtooths with shank,, of the type shown
. '
~
in Figure SO, or to f?t into quickchange chucks. In the
.are ro~ected frarn'a double face. The
latter cases the teeth p first
the second face are used -after the first
teeth projeat~.ng from
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(d)
a e] des of countersank
Figure ~6. [See also preceding p g
reamer's. .
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set of teeth is blunted. The teeth, particularly for machining
in cast iron, are hard-alloy. To maintain coaxiali.ty of the
hole and the work surface, the countersinks operate together
with the pivot journals`in the same manner as screwhead counter-
sinks. The pivot journals are either detachable, or integral
with arbor. Bracing with arbor is effected by a screw. Popu-
lar diameters for countersinks of this type are within the
range 11.E - LO millimeters. Due to the heavy-duty character
of the work, the number of teeth is not to exceed 2, Li., or 6.
Figure 58, a, shows the cutting 'parts of this countersink,
[Drawings]
Section EF Section AB Section CD
[Drawing] [Drawing] [Drawing]
[Drawings]
Figure 8. Countersink for trimming of face surfaces to fit into
quick-change chuck (with cam bracing).
Drawings]
Figure 59. Face-trimming countersink with square bracing.
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 the trimming of large surfaces are made with chip breakers
arranged in chessboard fashion Special notice is to be
taken of the countersink design shown in Figure 58, b suitable
for the trimming of surfaces inaccessible or inconvenient to
reach from above. The countersink has whole with parallel
sides, and the arbor end has an irregularly shaped cross
section. Such a design provides for the perpendicularity of
the cutting teeth faces about the tool, axis even when there
is some free play between the countersink and the arbor.
Bracing of countersink to ' arbor with the aid of a screw,
dowel, roller or ball, when these are present on the face
which is opposite to the location of the cutting edges, is
not as effective as the above described design.
the arbor to fit into a square hole in the countersink ch~nlr
and a thrust tapered washer abutting thecountersink. The
washer has a groove in it in order to facilitate connecting
with or disconnecting from arbor.
sink to the arbor, with the aid of a square tip at the end of
Combination Countersinks and Irregularly Shaped Countersinks.
In order to combine several operations (transitions)
into one, combination tools are used. A combination tool has
many advantages; (1) it allows the utilization of a standard
machine tool for complex machining, (2) it cuts down machining
time, thereby reducing production costs, (3) it reduces checking
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In order to facilitate machining, countersinks for
Figure ~9 shows another design for bracing the counter
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times since the precision of the work is insured by the proper
tool sharpening.
There are two alternate designs of a combination tool, It
is either made up of tools of the same type differing only in
size, or of tools of different types.
Outstanding examples of the first group are step
countersinks for holes with two, three, or more diameters
countersink, vari..type teeth for considerable
machining stock removal
[Drawings]
A convenient design of a two-step-countersink is
shown in Figure 60. Its characteristic feature is the
alternating disposition of boring and face-trimming teeth.
In contradistinction to the non-alternatin -tooth des,
g igns
the aiternating??tooth, design provides for a considerable
number Qf resharpenings. Countersinks with alternating teeth
are also used successfully/ for boring holes, hen , there is
considerable stock to be removed, The stock to be
removed
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 Declassified in Part - Sanitized Copy Approved for Release 2012/03/20 : CIA-RDP82-00039R000100240004-1
is distributed between two or three groups of teeth, which
are disposed on peripheral circles of various diameters
(see Figure 61). Each subsequent tooth overlaps the pre
ceding one. In designing the above, circumferences of the
requisite diameters are. drawn. By the requisite thicknesses
and height of the teeth, their central angles are determined
within such a range as to require the minimum number of
milling cutters for milling . thy; countersink flutes. After
the flutes have been milled, the teeth are sheared off,
heightwise and lengthwise, to conform with the amount of
surplus stock to be removed by each group of teeth, respec-
tively. Each group is usually made up of 3 -, though
sometimes of only two, teeth. To improve cutting, counter-
sinks are usually supplied with helical teeth having an angle
of inclination &) w l5 - 20 desgrees for the largest circum-
ference. It should also be remembered that angle L) assumes
lower values' for the other circumferences'.
Outstanding "examples of the second group are combiriaw
ton tools consisting of a drill and countersink, or reamer
and countersink, or boring cutters, countersink and reamer,
or other combinations.
Figure 62 shows combination tools for the machining
of a series of surfaces and flat surfaces, which are indicated
by corresponding markings on the tools and on the work.
blanks. Letter O indicates a roughing pass; letter Oh, `a
finishing pass,
87.
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The Geometric Parameters of Sectional
Countersinks, Thesis, Moscow Machine
Tool Institute, 19Li.1
No 11, 1936.
Leading Data on Countersink Operation,
ENINS, 195.
REAMERS
Designation and Types of Reamers
Reamers are designed for the machining of precision
holes. They are used for finish- and rough operations. In
relation to specifications, reamers produce holes within a
wide range of tolerances, from the fifth to the first class
of precision.
The correct work performed by a reamer depends on the
design and quality of its fabrication, as well as on oper-
ating conditions (cutting practice, cooling, the value of
the stock to be, removed, the `quality of the sharpening and
lapping of the cutting edges etc.)
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(1) by the nature of their application -- hand-operated
reamers (OST 2512 - 39), machine-.operated reamers (COST V
1672 1673 I.2), boiler 'reamers;
(2) by the shape of the hole to be machined
drical and taper (OsT `2i3 -~ 216 - 39);
(3) by the manner of bracing
insert reamers (4ST NKTP 3676);
cylin?-
().) by the tooth design reamers with inserted
teeth (GOST 883 16, ' 88La. h6, and 1S23 and roamers
with teeth integral with body;
(5) by the adjustability of dimensions -- adjustable
reamers and non-adjustable reamers.
The basic concepts, designations and terminology per-
taining to reamers are established in accordance with OST NKTP
Reamers wi h milled teeth4 This reamer is a cylindri-
cal body with flutes for the formation of cutting edges (Figure
63).
i Drawings]
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 3 degrees;` for ductile materials, such as steel, it is
12 1~ degrees. In the case of boiler reamers, it is 1.5
3 degrees.
Reamers with angle 7 L5 degrees on the cutting part
are very popular. Such reamers demonstrate good cutting ability
and a high degree of surface finish.
To insure free. entry into the hole, the smaller diameter
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tural elements: 1 - the working part; ll
CIA-RDP82-00039R0001 00240004-1
the cutting part;
the calibrating part; 13 -- the cylindrical part; 1
the back taper; 1 -- the shank; 16 -- the neck; e the
-- the tooth, k -~ the flute; s -w the front surface;
square, z ~
..w the back surface; a the front rake angle; 0`- -- the
t
back relief angle.
The basic elements of reamer design are the cutting and
the s,lxbratlng partss the number of teeth, the direction of
c
the teeth, the sharpening angles of the teeth, the pitch of
the teethgm oves, the flute profile; and the holding part.
The cutting (tapered) part 1 1 serves for the maxi
mum removal of stock. The cone angle 9 (in degrees), which
affects the durability of the reamer and the degree of finish
of the work surface, is accepted, in the case of hand-operated
.
reamers, as0.S 1, degrees. In the case of machine-operated
,
~
reamers} it is determined with relation to the work material:
 Declassified in Part - Sanitized Copy Approved for Release 2012/03/20
CIA-RDP82-00039R0001 00240004-1
of the cutting 'part is made smaller than the d'
xame ter of the
reamer by 1.3 l.L of the stock allowance for reaming, In
addition, 'a 145 w degree bevel is removed at the end of the
cutting part to prevent the teeth from chipping in the presence
of a heavier stock to be removed or
any defects in the hole.
The transition. from the cutting part g part to the calibrating part
is chamfered.
For the machining of light alloys, a special sharpening
of the cutting part is recommended, as is done in the. case of
fluteless taps. The lip an the cutting part is sheared at
an 'angle of 30 degrees to the axis and the flute is co.rres-pondingly deepened at an angle of 15 dagrees. Such a shaping
of the cutting part provides for a positive front rake angle
up to 8 degrees. To eliminate the possibility of weakening
the tool by such additional sharpening, the
width of the lip
is increased to compensate for the reduction in the. number of
teeth, .
Thy calibrating part 12 guides the reamer a.
n the work,
imparts precision and hlgh' finish to the... hole, and Insures
the presence of resharpening stock. An increase in length
12 results in harder work for the reamer
`' and in its iarnming
in the hole. it is, therefore, recommends
d that. in the case
of short reamers the length/
2
0.25 ? 0..3 of the ; reamer
diameter. A small value of 12 saves steel and reduces the
buckling of the reamer in hardening.
The back` taper .J Is made for the purpose
pux`p of reducing
x 91 .
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the friction between the reamer and the surface of the hole
and of forestalling the splitting of the hole by the cali-
brating part segment adjoining the neck. The lesser diameter
of the taper (at neck) is smaller than its greater diameter
by a value of O.OQ~ millimeters to zero, for hand reamers,
by 0.04 0.06 millimeters, for machine-operated' reamers'
and by 0.06 - 0.10 millimeters, for _oscillating reamers.
Due` to the small back taper in hand reamers, they
frequently have no cylindrical'segmento The reaming of par
ticularly clean holes of small length (up to 20 millimeters)
can be done with reamers without a back taper.
The number of teeth is usually even to compensate for
the error in measurement of the reamer diameter with the microM
. ? ; meter, in relation to diameter D in millimeters and the reamer
designation as per formula z x.1.5 + (2 i L)o For reamers
with a greater number of teeth, a greater value of z is
selected, since, with the increase in the number of teeth,
the degree of finish becomes higher.
In the case of boiler reamers, the number of teeth is
selected within the range from 3 to 8, in relation to the
diameters
Reamers are equipped with straight' or helical teeth.
Helical teeth provide for a better finish and higher durability
of tool. Straight-tooth rea:ners, when properly designed, re
'
Declassified in
. 92.
suit in holes fully satisfactory in :.precision and =surface `finish.
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 Declassified in Part - Sanitized Copy Approved for Release 2012/03/20 : CIA-RDP82-00039R000100240004-1
The fabrication, sharpening, and control of straight-tooth
reamers is considerably simpler than for helical-tooth reamers.
The machining of holes with longitudinal grooves of or length
0
ise-interrup,ed holes is to be done with helical-tooth reamers.
w
The hand of direction of the helical. teeth is to be opposite
to the hand of direction of the rotation of the reamer, in
order to eliminate the possibility of the self-tightening and
jamming of the reamer in the hole, and also to forestall the
possibility of the reamer shank becoming detached from the
machine spindle. The angle of flute inclination is selected
in relation to the flute material: for gray iron and hard
steel', it is 7 - 8 degrees; for malleable iron and steel
12 - 20 degrees; for aluminum and light alloys -~. 3S
degrees; for boiler work -- 2~ - 30 degrees.
The
eripheral_~non-uniform distribution of the teeth
in the hole being reamed forestalls the appearance of longi'
tudinal lines, 'which would be disposed in conformity with the
pitch of the teeth The cause for the appearance of a riffled
surface is the periodical variation of the tooth load, ac-
countable to the non-uniformity in the work material, to hard
or soft inclusions, and the like.
The non uniformity in patch may be attained by various
methods (see Figure 6)4), method b being the one in widest
use, since it provides for greater simplicity in the fabrica-
tion of the reamer and convenience in the microrneter~gaging
of its diameter,
.. 93 i.
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L0 o
1.6 148 ...- '.
t
k
0
00
10 3a ^0 3140 t c 36 37301 39 ? .
~o
12 2'7?30' 28o30 f 29o3o t; 30030! , 31?3o t 32030t
J~ I/yyg~ p
`
Yw.T4ruY11Wew4`N^+Y4x+M'hhN,H,~YaM1 nu.,.rh. A~. Iw, rx a^NMAILINWAI uWWlGbl{NCik1YAT '.eN1UwMNN++eihV,:xY.yf'C.T4
r.u?wwww__,~wwxf_w ?+r'M^wrfHn.TUeu,w+1U,~Naw.uH nurxlnuMrn+'mwrr.utraetvrw
Note: The dividing head disk is to have L9 holeso
Non-uniformity in the pitch of the teeth can also be
attained by slanting flutes with a change in direction for
each two adjacent teeth.
The angles for the cutting part are selected in rela~
ton to the designation of the reamer and to the work material.
Data pertaining to the non-.uniformity in the pitch of
the teeth is cited in Table 7.
Figure 6). Methods of forming a nonuniform pitch in the reamer
teeth. a pitch varied in all teeth; b pitch varied to
both sides of the control teeth lying on one diameter;
same values for pitch for each two opposite teetho
Non~uniforrnity in the pitch of teeth
Number of
teeth
Angle of turn
.....wmrwwwrwuwW,wu~sw,mww~rw++~s~wrw'wil.x~w.M+'w Woam4a4uMwnwwxnM+.wow:.,.,.~.:nwl.nwxne+aoxnvlYe+wT.r+'rrvwn:.N+m+mram+'wirrvuwlwrwu'rAV*7tTln WLLK~W:uwula~J1YMNTNk~M:M~Ar)'7xM1A4t"r'1~~".+'NMIS+N~~thA[Ib1k%
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wr,CYrM1I`wuRMU W WAn W MMa V TR~w~~MIVMM 4N1/'AdunbnlF'k?i W ~17u~T':AV MMRiVIV41 W A~tlM>wk~YMMO.MYMAAw~ W~M1M1~N f Vt~fMT[ NNI#YdF1MM!N!b51Y:0~7JMN}4kJ':
i
903 t 6200.,.
00240004-1
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Back relief angle ~X, for the cutting pare is selected
within the range of L - 8 degrees. For finishing reamers,
The sharpen-
point, while, on the `calibrating part, a small `margin is left
(Figure 65)o The margin provides for the guiding of the
reamer in, the hole, promotes a smoother surface finish, pro-
vides for proper. calibration of the hole' and facilitates
the control of the reamer along its diameter. The margin
width is selected as 0.05 - 0.3 millimeter, in relation to
reamer size. In the machining of ductile materials, when
it becomes necessary to prevent the adhesion of the chip,
th.e margin width is reduced to 0.05 - 0.08 millimeter. The
grinding of th.e margin at an angle of 30' - 1030 ? is also
recommended. In the case of hand reamers, and also machine-
operated reamers with chrornated edges, the margin width is to
be kept within 0.15 - 0.18 m liimeters? The margin width in
machine-operated reamers may be increased to Oa3 - 0.1L. milli s
meters, when machining holes of special precision in steel
and cast iron' in which case the reaming is done by mechanical
feed and at low cutting speed.
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Adjustable cylindrical reamers, and also taper and
bailer rearnerss are to be sharpened to two angles: G 8 degrees and c` - 1 20 degrees (Figure 65, b)
Front rake angle of the reamer is accepted as
equal to zero; the front surface is directed along the radium
In the case of more rigid specifications pertaining to the
finish, it is recommended that angle be given a
surface
negative value of minus degrees. In order to avoid the
adhesion of chip to the cutting edge when reaming in ductile
material, angle 7 is to have a positive value within the
range of - 10 degreesa
In the case of boiler reamers, which are not only to
remove the predetermined machining stock but also the layer
of mewl formed by the boiler plate displacement, angle
is to be positive within the range of 12 - l~ degrees.
Angie 7 is measured in a plane normal to the direction`
of the, flute. The ratio between. angle in a normal section
and angle in the face section (for a point located at the
~
periphery) is expressed by formula
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where a is the angle of flute inclination.
 Declassified in Part - Sanitized Copy Approved for Release 2012/03/20 : CIA-RDP82-00039R000100240004-1
3 w 3.~
6
- 5
6
5
6
om2~ 0e12 8
o03 0.12
0.14 0.12
6 oo odS 8;
0.6 001 9C
Dimensions and types of flute profiles are enumerated
in Table 8
TABLE 8
Dimensions of reamer flute profiles
Diameter Number Width of lip
(margin) in
of reamer of p
teeth in mm r,n degrees
i ra mm
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hype A Tae B
[Drawing] [Drawing] [Drawing]
] [Draw~.ng ]
Figure 66. The profile of the reamer flutes,
[Drawings]
Figure 67. The milling of the flutes with the aid of a double
angle milling cutter.
CDrawing
I.Lute) is free of the above defects. For medium and large
sizes, the use of a profile with the outline of the back of
the tooth along the radius (for type B flute) is recommended.
Such a profile provides for an adequate space for the chip
and the requisite strength of the tooth.
A single angle milling cutter (for type A flute) (see
Figure 66), makes a poor front surface, and the face milling
teeth wear rapidly. Due to the undercut, in the tooth this
r ~
type of milling cutter is not suitable for milling helical
teeth reamers. A double-angle milliri~ cutter
~ (for ..type B
In order to avoid the appearance of cracks in harden,..
g, the hollow of the flute is to be rounded to a radius
0.3 08 miJ.limoters,
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When milling a flute for a reamer of non-uniform pitch
(Figure 67), in order to maintain the same value of p, it
becomes necessary to change the depth' of the flute and the
distance between the axes of the reamer and the milling cutter
for each new flute0
.5iILL&L !T
where R 3 is the radius of the blank (with a stock allowance
of 0.1,E - 0.11 millimeter for grinding).
To simplify the operation of milling the flutes, special
shape milling cutters are used, which machine not the flute, but
the tooth of the reamer (see Figure 68), with the width of
lip p remaining the same, without a change in the depth of
milling. The defect of the special shape milling cutters
consists in the fact that the back of the tooth receives a
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Figure 70. Duplex special shape milling cutter for the milling
of reamers.
The special shape milling cutter may be replaced' by two
milling cutters' assembled into one duplex unit (Figure 70),
with the width of lip p adjustable by an intermediate ring.
The profile dimensions for' special shape milling cutters
are given in Table 9, and th.e designations of the profile corn-
ponents are shown in Figure 71.
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small shoulder a, 0 l - 0.2 millimeter high (Figure' 69).
This method of milling with special shape milling cutters
is applicable to straight-tooth reamers only
 Special shape `milling cutter profiles
Figure 71)
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in degrees
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The clamping part of hand reamers consists of a short
neck 16, straight shank 1, and square e. The neck 'serves to
facilitate the grinding of the cutting part and shank, the
square for bracing in the respective' hollow, the shank for
0.03 - 0.08 millimeter smaller than the reamer diameter.
The clamping part of machine-operated reamers is made :
(1) cylindrical, for reamers up to 10 ? 12-millimeter size;
(2) with Morse taper; (3) with square (not in wide use).
Machine-operated reamers have a long neck to facilitate the
reaming of deep holes.
Detachable reamers are made with tapered holes, the
taper being 1:30.
OST 2811 - Lt0.
..A diagram of the 'disposition of diameter tolerances
for reamer, designated for the machining of work with depar-
tures by a system of holes, is shown in Figure 72, The values
for the tolerance components are given in Table 10.
Nominal 0
Figure ?72. Tolerance diagram for reamer diameter: N ? tolerance
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 Declassified in Part - Sanitized Copy Approved for Release 2012/03/20
for non-precision of fabrication; Pmax and Pin .._ markings
off values of the hole being reamed; T p? guaranteed reserve
of wearing stock along diameter of reamer under operating con-
ditions;
tolerance for hole; AB -- upper departure of
reamer diameter; CD -- lower departure of reamer diameter.
Reamers of Sectional Design.
Reamers of sectional design are divided into release
reamers and inserted tooth reamers. Release' reamers are used
in assembling work. Their teeth are made integral with body,
but they r spread along the diameter, due to the combined action
of axially cut out splines and an adjusting taper screw or
ball in a specially bored hole.
Inserted tooth reamers come in various designs; the most
1 I~
rational being the design where the teeth are inserted into
the body with the aid of riffles. Bracing and adjusting to
i~ size is effected in the same manner as in the case of counter"
!
?~ < sink teeth (see original page 338)
Sectional reamers are made with a small number of `teeth;
Diameter of reamer Number of teeth
(in millimeters)
CIA-R D P82-00039 R000100240004-1
8
10
130 Mlo 12
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These reamers are also made with non-uniform pitch, in
accordance with data presented in Table 7.
Tool angles and cutting and calibrating parts are the
same as in the case of solid 'reamers.
It is recomrrlended that concavities be made for each
tooth in the body of the reamer, along the cutting edge, to
facilitate the ejection of the chip.
Specifications for inserted tooth reamers are estab-
lished by GUST 1523 ? 42
TABLE 10
Tolerance components for reamer diameter
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Tolerance values in microns
(3) () () (6) (7) (8) (9) (10)
ntmr+n.., wtaae! r n atxea arvrx?~+va, nr srtm~sra;, srxsn r
7 910 12 iii. 16 18
Second class 7 9 11 12 1?'. 16 18 20
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pirst class ~ U y" -- ~
Precision toler-
aces in fabrication of 'precisian
a
N o 12 1~ 1 l 2p 20
Second class 1
of precision
Taper Reamers
Taper reamers are used far the reaming of a cylindrical
for the calibration of an already tapered
hale to a taper, or
holes prelirinarily machined by another tool.
Taper reamers are made in the following types:
7 or 1:10};
for Morse taper hoJ.es; (2) for tap hales (taper l:
(3) for dowel p s (toper 1:~p); (L) Coal rea.t~1ers for
'~.n hole
detachable tools, reamers, countersinks, etc.. (,apex 1:30)?
Taper reamers for Morse toper holes (Figure 73) are
three or two. The first set (Figure 73,a)
fabricated in sets of
is :>.n the form of a countersink, threaded at an angle of inclina-
to the inclination angle of the Morse taper. The
tion equal
coincides with the direction of cut. The
lead of the thread.
reamer converts a cylindrical hale into a step hole. The
at their back surfaces, their number ranging
teeth are relieved,
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00240004-1
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[Drawings]
[Drawings]
[Drawings]
Figure 73. Taper reamers for Morse taper holes; s - thread
height of tooth; k
width of thread flute; a ?- depth of thread flute.
The second reamer (Figure 73, b) has rectangular left-
from 3 to 8, in relation to the taper ratio. Each projecting
part performs with a small angle, similarly to a boring cutter
with 'face-cutting edge.
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hand thread (for right-hand cutting). The thread is for the
purpose of breaking up the chip and for effecting smaller
steps in the hole. The number of threads per inch in 8 w
in relation to the taper ratio; b = s; a b; the
S
2J
teeth are sharp-pointed, with small 1 T millimeter margin.
The third reamer (Figure 73, c) is little. different,
in its design, from a cylindrical reamer. The pitch of the
teeth is uniform. The margin width is 0.05 0.08 millimeter.
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CIA-R D P82-00039 R000100240004-1
Taper reamers for tap holes and tools come wit1l one
reamer in each set. The elements of design are determined in
th.e same manner as in the case of conventional cylindrical
reamers."
Reamers for dowel pin holes serve for the reaming of
already existing cylindrical holes in various parts of machines
connected by dowels. Due to their small taper ratio (1:~0),
they remove an insignificant layer of metal, and, therefore,
convert a cylindrical hole into 'a'tapered one without prelimi-
nary reaming. The front end diameter is 'so calculated that
the reamer projects 1.~ - millimeters from the hole, To
increase the number of possible sharpenings, the cutting part
is made longer than the standard dowel length. The number of
teeth is within the range of Li. to 6. Reamers up to the - 8
millimeter size are equipped with reversible centers. Reamers
up to the 3 millimeter size are of trihedral or pentahedra)
shape, in section, the ribs serving as the cutting edges..
Screw dowel reamers,; the design ofi which is depicted
in Figure h, and the sizes enumerated in Table 11, permit
high cutting speeds and are characterized by great durability.
[Drawing]
Figure h.o Screw-dowel machine-operated reamer.
108
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Screw-dowel machine operated reamers
dimensions in 'millimeters)
(
direction of the helical teeth is opposite to the
The
direction of cut, ~ ting thereby the possibility of self
el~.ma.na
tightening of the reamer. The flutes provide ample space for
the chip, inating the possibility of jamming. Hand-operated
el- ' ~-m
reamers of this type differ from the chine-operated ones by
teeth (3 M L,) and the greater value of
the greater. number of
imeters). The angle of the milling cutter
pitch (12 .. 60 mill
used in is 75 degrees. In the remainin
~.n their fabrication
0
8
o.
0.2
80?
Lo
2
Oob
0.
0.8 -
0o2
80?
7.2
'26?
1.0
0.3
80?
9.0
260304
?
4
1L
2r~o30 ~
1.6
o.~
80
0
1~0
o.b
80?
90
26?3o~
1$
o.8
80?
11.2
26?
ld
l.o
80o
13.
26 ?
.~ er of the milling cutter for milling
Note:` ~'.... width; ~T angle of p
of, the reamer flutes.
1 10
8 1 lE
10 2 20
13 2 2y
16 2 30
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features, the designs are similar.
Hard-All oy-TTDied Reamers
of hard alloys in reaming is stipulated by
The use
wear and by their relati vo7..y low
their great resistance to
sensitivity to the nonahomogerzeity and inczstations in the
work maters al.
Hard?~loy~t~.pped reamers permit the application of a
- ,..
cutting speed several times greater than. is possible with
highspeed steel reamers.
the accumula~3i0 n of grease on the
In order to avoid .,
rinding the reamer teeth, the length of
grinding disk when g
blades is calculated to be the exact length
the hard-a7.loy
of th.e working parts which, in turn, is made shorter by one
in the case of conventional reamers. Carbon
third than
ea~ler body, the carbon content being
steel is used for the r
o.6 Q7 percent. This ' s p' ermssible, s~Ce ::.the body of
or .: ~.
resence of teeth along the full
the reamer, due to the p
t, does not comp: into contact with:
length of the working par
the work surface. The thickness of the hard?a].10y blades
otherwise it would be Impossible to
must not be too great,
use them a. ?n the case of small size reamers. The thickness
of the hard-alloy blade is usually equal to 1/10 - 112 of
its length.
front rake angle: = 0, the back relief angle
The f
the cutting angle = 2 degrees;
12` t 15 :degrees,
110 ?.
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the bevel on the face is one millimeter X L degrees. The
back taper runs within the range of OuO15 = 0~02S millimeters
For reaming blind holes, it is recommended that the reamer
be equipped with face-cutting teeth.
For the machining of deep holes, three'-tooth short
reamers with brazed-on hard-alloy blades (T15K6), equipped
with a hardwood front guide, are used. The cutting angle
9p = 75 degrees; the back relief angle upon the cutting
7
edge is ~C?W 3 degrees. These reamers work under conditions
of intensive cooling during accelerated cutting speeds.
1 hen machining in hard metals with 1 > 90 klom
grams per square millimeter, trihedral reamers Without milled
flutes are used. The hard-alloy blades are brazed into the
grooves, disposed at the apexes of the trihedral section of
the body, in such a way that the front rake angle 1) has
a negative value. The back relief angle O( = 8 degrees.
The back taper is made to an angle of 2 degrees. Such reamers
operate at high cutting speeds -up to 80 meters per minute.
BIBLTOGRAPI{Y AND SOURCES
1. Kutay, A. K., and Shtermer, G. A., Tolerances, Reamers,
and Countersinks, ONTID 1936.
2. Semchenko, I. I., Cutting Tool, volume I, ONTI, 1936?
3. Chetverikov, S. S., Metal Cutting Tools, Mashgiz, 1915.
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