Circular fixture which mounts several specimens within a single turret prevents specimen smearing during grinding and polishing operations performed on a vibratory lapping machine. Each specimen is loaded individually with a weight small enough to prevent smearing but large enough to promote polishing

Matras, S.

English

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AEC-NASA TECH BRIEF
cia 
say 
rEs
December 1966
	
Brief 66-10562 
AEC-NASA Tech Briefs describe innovations resulting from the research and development program 
of the U.S. AEC or from AEC-NASA interagency efforts. They are issued to encourage commercial 
application. Tech Briefs are published by NASA and may be purchased, at 15 cents each, from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
--° 
Metallographic Holding Fixture Permits Polishing of
Soft Metals on Vibratory Lapping Machine 
Specimen Holder 
(Lucite)	 Specimen Loads 
Specimen Holder Well 
Rotating Carrier 
(Lucite)
Spacing Lug 
(3 per Holder) 
Locking Nut 
Loading Nut
\	 Specimen Mount 
Washer 
Friction Disks 
Teflon Bushing
Center Post
NOTE: Double Arrow Lines 
Denote Direction of Rotation 
The problem: 
To prevent specimen smearing during grinding and 
polishing operations performed on a vibratory lapping 
machine. Rotary impulse grinding and polishing 
machines cause smearing of soft metallographic speci-
mens, such as uranium, when the specimens are in-
dividually loaded on the machine bowl. The specimen 
load, which is necessary to produce adequate contact 
force between the specimens and the polishing surface, 
and which furnishes sufficient inertia to effect 
slippage between these surfaces, is so large that 
smearing of the polished surface results. Also, single-
specimen mounts tend to overtake one another and to 
gather at the periphery of the bowl, wearing the 
polishing surface along a narrow band and decreasing 
the rate of metal removal. 
This document was prepared under the sponsorship of the Atomic 
Energy Commission and/or the National Aeronautics and Space 
Administration. Neither the United States Government nor any per-
son acting on behalf of the United States Government assumes any
The solution: 
A circular fixture which mounts several specimens 
within a single turret and therefore requires less 
specimen load than was previously necessary. Each 
specimen is loaded individually with a weight small 
enough to prevent smearing but large enough to pro-
mote polishing. The inertia of the entire turret is 
imparted to each specimen to produce the desired 
rubbing effect since the specimens are yoked together 
through the turret body. 
How it's done: 
The fixture consists of a disk shaped lucite turret 
containing six equally spaced holes for specimen 
holders, and a lucite bowl which replaces the stainless 
steel bowl normally used on the vibratory unit. A 
lucite cylindrical specimen holder fits inside each of 
(continued overleaf) 
liability resulting from the use of the information contained in this 
document, or warrants that the use of any information, apparatus, 
method, or process disclosed in this document may not infringe pri-
vately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19660000560 2020-03-11T17:44:24+00:00Z
the six holes in the turret. The six holders are free to 
rotate and slide axially within their respective turret 
recesses. Each holder contains three equally spaced 
holes, each of which accommodates a specimen and its 
loading weight. The specimens and weights are free to 
rotate and to slide axially within the holders. 
A circular polishing cloth is fastened to the bottom 
of the bowl. The turret is then center mounted on an 
axis extending through the center of the bowl so the 
turret may rotate about the axis without touching the 
polishing medium. An adjustable snubbing device 
connected to the axis and to the turret allows the 
rotation of the turret to be restrained or braked. The 
six specimen holders are inserted in the turret recesses 
so the three spacer lugs on the bottom of each holder 
rest on the polishing medium. Specimens are then 
dropped face down into the holder recesses so they 
rest on the polishing surface, and the proper weight is 
placed on each specimen. Ethylene glycol is used as a 
liquid interface between the specimens and the weights 
and along the holder recess walls. 
When the vibratory unit is activated, the vertical 
and rotational movement of the unit causes the turret 
to rotate. As the snubbing unit is tightened, the 
turret rotation is reduced. The polishing surface 
therefore rubs against the specimen faces and causes 
the holders and individual specimens to rotate within 
their recesses. A rubbing action and three rotational 
movements are thus imparted to each specimen. Soft 
specimens attain a very acceptable surface finish when 
this fixture is used, and the controlled rotation of 
the specimens spreads wear over a large area of the 
polishing medium.
Notes: 
I. The springs within the vibratory unit may be 
changed to reduce the vertical component of motion 
and thus eliminate the tendency for specimens to 
bounce on the polishing surface. 
2. Variations of this fixture, without the center 
mounting feature, may be used for the preliminary 
grinding of specimens in addition to the final 
polishing operation described. 
3. Inquiries concerning this innovation may be di-
rected to:
Office of Industrial Cooperation 
Argonne National Laboratory 
9700 S. Cass Avenue 
Argonne, Illinois 60439 
Reference: B66-10562 
Patent status: 
Inquiries about obtaining rights for commercial use 
of this innovation may be made to: 
Mr. George H. Lee, Chief 
Chicago Patent Group 
U.S. Atomic Energy Commission 
Chicago Operations Office 
9800 S. Cass Avenue 
Argonne, Illinois 60439 
Source: Steve Matras

Metallurgy Division
(A RG-42) 
Brief 66-10562	 Category 05


Metallographic holding fixture permits polishing of soft metals on vibratory lapping machine

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