GERMAN TECHNICAL PUBLICATION

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78-03172A000300050001-4
• Release Decision: RIPPUB
• Original Classification: S
• Document Page Count: 12
• Document Creation Date: December 22, 2016
• Document Release Date: April 10, 2012
• Sequence Number: 1
• Publication Date: May 25, 1955
• Content Type: MEMO

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-*W-- *
COL 1Lo-f
Memo #A-10
25 May 1955
MEMORANDUM F(R: Assistant Chief, TSS for Technical Aids
SUBJECT : German Technical Publication
In response to your request, a translation of the subject
publication has been made by FDD and is forwarded herewith for
your retention.
Chief, TSS RUTH DS
Attachments
German Technical
Publication w/translation
Distribution:
2 - Addressee
1 - TSS/SRB
2 TSS/AUTH/tDS
TSS)
00 86
000 O IIEY DATE 22 JUL 8 BY
TYPE
GRID Camp ON
0RIC C.**$ PAGES /ate RAY CLASS
'-?-L- NEXT REY_..-_O/a A.11THI HR 13.2
JUST
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A New Type of Ultrasonic Boring Tool
F?GN D0CLf1L-'iTS DLV1SIOIy,
755'23y
AL
For thousands of years holes have been bored in things. For thousands of
years boring has been thought of in connection with a rotary motion. The
revolutions per minute of the boring tool can be quite varied; they can be
less than one revolution per second, or they can be several hundred revolutions
per second. The boring tool, in any case, has always rotated. One more thing
we take for granted in reference to a boring tool: the tool must be extremely
hard, at least much harder than the material thru which the hole is to be bored.
Only in the case of the diamond is this rule not axplied, for there is no
material harder than diamond. For boring thru the hardest materials a boring
tool with a diamond point is used. The most common boring tool is made of
high-quality steel; with this tool all materials which are softer than the
steel can be bored. With all these boring tools the holes bored have always
been round. Very often, however, a hole with corners or irregular shape is
desired. Here the rotating boring tool cannot be used. It is therefore obvious,
that the attempt has been made to design a boring tool which will not rotate but
move back and forth on its longitudinal &xxis. This is only possible, however,
when the material to be bored is very soft. The rotating boring tool is a
chip cutting tool and thus has a good cutting quality. On the other hand, a
boring tool which moves only in its longitudinal direction works like a chisel
and cannot be used satisfactorily even for such soft metals as copper and bronze.
A new idea led to the use of longitudinal oscillations of the boring tool.
This idea was developed thru the well-known air hammer with which rocks can be
broken up (but no holes bored) to the rapidly vibrating boring tool. Higher and
higher frequencies of vibration were tried until the surprising fact was discovered,
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that ultrasound (inaudible oscillations) can be used as a driving power for
boring tools.
The boring tool which operates on the principle of ultrasonic vibrations
along the longitudinal axis can be improved in operation very much by the use
of a pulverized grinding material made of the hardest substances; these small
particles themselves are caused to vibrate at ultrasonic speeds, and they,
rather than the tool itself, attack the work and produce the boring. The use
of this grinding powder has another advantage: if finely divided carbides or
diamond powder 4I used, the very hardest materials can be bored. The tool
itself does not have to be made of hard or expensive material, since it does
not come into contact with the work. The operation with this boring powder
is also an efficient and simple one. The powder can be supplied continuously
suspended in water. The cutting is constant, and the water acts as a coolant.
A basic consideration in the design of the oscillating boring tool is the
elimination of disturbing noise. Technically, it would be possible to use this
type of boring with oscillations of only a few hundred or a few thousand oscillations
per second, but such an operation would make the boring tool a source of noise
equal to a loudspeaker with several hundred watts output. For this reason, the
boring tool had to be designed to operate with more than 20,000 oscillations
per second, so that the sound produced would no longer be audible. It was this
consideration which led designers into the area of ultrasound.
Except in special cases, the ultrasonic boring tool operates most efficiently
with oscillations between 20 and 30 kilocycles. Frequencies below this range
would produce a disturbing audible noise, and frequencies above this range would
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would not be feasible, since the magnetostrictive efficiency, which is above
70- at 25 kilocycles, decreases ar,proximately inversely with the frequency beyond
this point. For example, it is only about 20% at 100 kilocycles. Another
disadvantage with higher frequencies would-be the fact that the length of the
boring tool would have to he decreased as the frequency increases, so that with
a frequency of 100 kilocycles the boring tool could only be 3 centimeters long.
Only where extremely fine borings with extreme precision are required is it
feasible to use frequencies of about 100 kilocycles.
The ultrasonti boring tool "D ron" (see Figure 1) is made of several
parts. An electric high-frequency generator, generally a twos-stage electron
tube oscillator, produces the necessary high-frequency output (about 600 watts
in the illustrated model), which can be regulated by a special knob. This
output is led to the so-called sound-head, which converts the electrical
oscillations into mechanical oscillations (see Figure 2). The main part is
a specially shaped rod of a high-quality nickel alloy surrounded by a coil thru
which a high-frequency electric current passes. This rod is'Amersed in oil, which
is cooled by water passing thru a surrounding copper coil. This cooling is
necessary, since the oscillator, with only 70% efficiency (3010 of the high-
frequency output is converted into heat), would heat up too much without it.
The actual boring tool, discussed below, is screwed on to the nickel rod.
The sound-head is attached to a mechanical precision mounting, which in turn
is mounted on a drill stand. This precision mounting, as in the case of the
conventional boring Lachine, has two functions: it must position the tool with
the greatest possible accuracy in a vertical position to the surface of the
work and must supply an adjustable spring force against the work corresponding
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"Y it to i a.. I
to the size of the boring. With the ultrasonic machine, these two mechanical
functions have considerably greater requirements than in the case of the
conventional boring machine. The design of the drill stand varies according to
the use and precision requirements. The stand illustrated in Figure 1 has
a high-precision horizontal table to provide for accurate boring of several
holes in a single piece of work. Finally, there is a pump to supply a steady
stream of abrasive material to the oscillating tool. This material, boron
carbide in water suspension, is supplied near the top of the tool to provide
cooling over a large area of the tool surface. The abrasive material flows
down the outside of the tool and provides a constant supply at the boring spot.
This design has a maximum efficiency when the tool itself is tuned as
close as possible to the resonant frequency corresponding to the natural frequency
of the magnetostrictive oscillator, and when the electrical high frequency has
the same resonant frequency. The sound-head and the tool form a coupled
oscillating system. Such a system oscillates with maximum amplitude when the
natural frequencies of the individual oscillators are the same, and when the.
oscillating impetus is produced at the same frequency. The oscillations of the
generator and the tool are purely longitudinal. If the tool were struck with a
hammer in the axial direction, it would produce attenuated longitudinal oscillations
at its nr+tural frequency. Since it is not struck a single blow by a hammer, but
is oscillated continuously by a high-frequency generator, its oscillations are
not damped, i.e., it oscillates with a time-constant amplitude. This amplitude
is naturally at a maximum when the oscillation is equal to the natural frequency
of the tool. Since sonic velocity in steel is equal to about 6000 meters per
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second, the wavelength of the longitudinal wave in steel at 25 kilocycles is
6/25 m or 24 centimeters. The natural frequency of a rod is computed from the
rule that the wavelength is twice tlteV-the length. Consequently, the correctly
tuned tool of an ultrasonic boring machine for 25-kilocycle operation must be
12 centimeters long. Correspondingly, as mentioned above, a tool for 100-kilocycle
operation would have to be 3 centimeters long.
These specifications apply strictly only when the oscillating tool has a
constant cross section over its entire length. Such a shape is used for the tools
of an ultrasonic drilling machine only in very rare cases. ictually, the tool of
such a machine almost invariably has a conical shape (see Figure 3). This shape
is used because the tool,which transmits the oscillation energy from the sound-head
to the working point, must at the same time be a mechanical matching transformer.
The oscillator in this case has a constant radiating surface of about 10 square
centimeters. The amplitude is distributed. uniformly over this surface and, at
a given frequency, depends only on the supplied electrical high-frequency.
The effective area of the boring tip, however, is in most cases smaller than
10 square centimeters and varies according to the size of the hole to be bored.
The total oscillation energy must be transmitted from the large radiating surface
to the much smaller surface of the boring tip. If this occurs without loss,
the oscillation amplitudes behave in a manner opposite to that of the surfaces.
Since this is the case, a definite conical shape is necessary for the tool.
Because of its shape, it will.be referred to as the "boring snout" in the following
discussion. It thus performs at the same time the function of a mechanical
matching transformer similar to t'nat of an electrical transformer. The optimal
form of the boring snout can be computed. For this reason, each ultrasonic
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boring machine is supplied with characteristic tables from wr:ich the optimal
form for the boring snout can be read off for any desired purpose.
It is naturally not necessary to use a different size boring snout for every
square-millimeter chant-e in the size of the hole to be bored. In general, an
assortment of from 3 to 6 boring snouts, each for a certain range of hole diameters,
can be used. If an energy loss of a few percent occurs, it makes no difference,
since the loss can be compensated by the high-frequency ,enerator. Any losses
which occur lead to additional heating of either the oscillator or of the boring
snout. This heating, however, is kept low by the above-mentioned cooling systems.
The oscillator (Figure 2) is capable of radiating almost 500 watts of ultra-
sonic power on a surface of 10 square centimeters. This means that the maximum
surface load is 50 w/cm2. Such a load requires a high tensile strength for the
oscillator material, since we are dealing with longitudinal oscillations. Special
alloys hid to be develo?ed, which have high tensile strength and magnetostrictive
effect and the lowest possible losses. The losses are the customary electrical
eddy currents, hysteresis, and other magnetic losses, which we shall not discuss
further here. The boring snout must have even greater tensile strength and higher
elastic qualities than the tool itself, since there is a concentration of energy
on the smaller cross section of the snout. If such a boring snout were diminished
in cross section from 10 square centimeters to 1 square centimeter, the specific
surface load at the tip would be tenfold, or a maximum of 500 watts per square
centimeter. Such a density of energy cannot be supported by even the highest
grade steels. The forces of tension and compression occuring in the ultrasonic
range at 500 watts per square centimeter w,uuld far exceed the elastic limits and
cause an intense heating of the material, followed ultimately by fatigue break.
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Thus, if the diameter of the hole to be bored is small, the ultrasonic boring
machine cannot be operated with full power. It must be remembered that a boring
snout tapered down to a few sqare centimeters, when operated with 500 watts
ultrasonic power, can be brought to a red glow in a:ivery short time.
Special alloys of copper and nickel with elastic limits 2 to 3 factors higher
than those of high-grade steel are available on the market. With a boring snout
made of such an alloy (for exampel, of monel metal) the boring speed can be
increased f.0 Y'small holes, since this material can stand a higher ultrasonic
stress than steel. The price of such alloys, however, makes their use feasible
only in very rare cases.
There are v-'ry many uses to which the "Diatron" can be put. We have already
mentioned that the shape of the oscillating tool or the hard tip SINIM does not
have to be round, but can be used in any shape. Thus, holes with the most varied
shapes can be bored (see Figure 4). Another advantage is that any hard material
can be drilled as long as the abrasive used is harder than the work. The most
welcome area of application is the working of cemented carbides for the production
of stamping dies. Up until now, punches and dies for precision parts such as
those produced in the watchmaking industries have been made of tempered steel;
now they can be made better and cheaper out of cemented carbides with the aid of
the ultrasonic boring machine.
By adhering to a few important rules in the operation of the "Diatron"
accuracies of within a few thousandths of a millimeter and surface roughnesses
of less than one-thousandth. of a millimeter can be obtained. The working process
at the tip of the boring tool is actually made up of two processes: The granules
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- -I - ,I y{;
of abrasive material, dancing to and fro at ultrasonic frequencies between tool
and work,act like microscopically small chisels and perform the actual boring
process; some granules of the abrasive mAerial move parallel to the tip of the
boring tool as soon as it moves down into the work and thus 1,olish the sides of
the hole, Even though the tool oscillates in a purely longitudinal direction,
this polishing effect produces a slightly conical shape to the hole, since the
polishing continues for a slightly longer period of time at the end where the
tool enters the work.
If a single boring is made with high precision in a 5-millimeter thick
plate of cemented carbide, the diameter of the back end of the hole will be
about 1/10 millimeter larger than the diameter of the front end. Such a stamping
die can be nut to good use, since a slightly conical shape is desir' ble. In
such a case, only the side of the boring which was underneath during the 0
should be used as a cutting edge for the die. If such a plate were to be
polished sev?ral times, as is usually necessary in mass production, the boring
would become perceptibly larger, because of its conical shape. This can be
overcome by using two or three boring tips of slightly varying size. With the
first tool, the hole can be cut 2/10 millimeter undersize, the second tool
can be 18/100 millimeter thicker, rind the last tool can be the exact size desired.
It is also well to use different grades of powdered abrasive material. The
boring speed with coarse n abrasive (granulation 5 to 10 A) is much
greater than with the finest abrasive powder (about 1 /4 granulation). Thus,
the first section of the boring will be made with coarser abrasive. Nevertheless,
the time necessary for the first boring will be ten to one hundred times longer
than that necessary for the subsequent borings, since the first boring removes
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DA
of the material. Thus, the undesired polishing effect at the back end of
the boring, which produces the conical shape of the hole, is also strongest during
this initial boring operation.
The boring time for the second and third tools is much shorter, because these
tools do not have to wear away very much material. Correspondingly, their polishing
time and tendency to produce a conical hole are reduced. The accuracy of any
certain procedure depends, naturally, on the type of boring, length, shape, and
material worked. Of course, the number of different sized tools used in a sings
operation can be greatly increased in order to obtain greater precision. In
any case, only a small amount of additional work with polishing paste is necessary
in order to give the borings a surface quality required for punches and dies.
If larger holes are to be produced, the core can be punched out or removed
with an electric,-are cutting tool before the ultrasonic boring is applied.
Electric-arc cutting is much cheaper, but has nowhere near the accuracy and
surface-quality results of the ultrasonic method. Electric-arc cutting is also
limited in application to metals and materials which are electrically conductive.
The ultrasonic method, on the other hand, can be used on any material, including
porcellain, sintered boron carbide, precious stones and semiprecious stones.
The tip of the tool of the ultrasonic boring machine wears down during the
boring process. It gradually becomes rounded. This is not serious in the case
where holes with parallel sides are driven thru the work. With blind holes, or
holes with sides which are not parallel, a frequent sharpening or eatchanging of
the tip is necessary. The tips, which are brazed to the snout, can be exchanged
in about a minute with a small appurtenant high-frequency induction-heating unit.
The more brittle the work is, the easier it is to work with the ultrasonic
method. On the other hand, the boring capacity is lower, the 7Ngr,~?s}'the work is.
. ^
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9
The tool tip should be made of the toughest steel, so that the wear of the
tip will be much less than the wear of the work. It must be remembered that
the ultrasonic method is not advisable when the work is a ductile material.
Heat-treated steel is easier to work, the deeper its penetration hardening is.
In no case should the ultrasonic method be used on work which has only a surface
hardening. With such material, the first stage of boring thru the hardened outer
surface goes very rapidly, but then the speed of boring decreases considerably,
and it is possible that a continuation thru the work could produce a greater wear
of the cutting tip of the tool than in the work. The limits for the use of the
"Diatron" should always be kept in mind, since it is designed for use on only the
hardest and brittlest materials. It should be remembered that the "Diatron" can
produce punches and dies of cemented carbides in a much shorter time than that
required to make them out of tempered steel. In view of this new process it is
therefore strongly recommended that cemented carbide tools be used in those areas
where they heretofore have not been able to be put to.use because of their poor
machineability.
The production of stamping dies has been consciously emphasized in the
application of the ultrasonic boring machine. There are, however, countless
other possible applications. We might mention the production and machining of
spraying nozzles or pressed shapes for the plastics industry, the boring and
polishing of jewel bearings, the machining of small precision dies, and work
in the jewelry industry. It must be remembered, however, that in the production
of holes with sides which are not parallel, the cutting tips must be retooled
more often than in the drilling of straight-thru holes. The ultrasonic method
can also be used variously in the machining of hard industrial porcelain, quarta
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crystals and quartz plates. For the production of round holes in such materials,
however, the use of the more expensive rotary diamond drills is actually more
economical than the use of the ultrasonic method. In all other cases (where the
holes to be bored are not round) the ultrasonic method is preferable. The
same applies for boring round holes also, whenever the number of holes to be
bored is too small to justify the purchase of a precision diamond drill, and
the cost of an ultrasonic drill is extremely low.
Wilhelm Lehfeldt, Heppenheim (Hessen)
M
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