Simple, inexpensive device can be attached to most metallographic sample polishing tables. It provides a suitable surface finish for microscopic examination or photography of surface details of the samples

Adkins, J. M.

Bernett, E. C.

English

NASA Technical Reports Server

Noveniher 1969	 Brief 69-10596 
NASA TECH BRIEF	
a 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Automatic Sample Rotator for Metallographic Polishing 
Frictioi 
Positioniri 
Tubular
Ba 
Bar Lock
Ring	 Roller 
Figure 1
ection 
md Bowl 
Polishing Wheel On Polishing Table 
haft Extension 
Sample Carrier 
lurry Election Hole 
sulient Drive Rings 
shung Cloth 
The problem: 
Metallographic samples must be polished to provide 
a suitable surface finish for microscopic examination 
or photography of their surface details. Surface finish-
ing as conventionally performed begins with mounting 
a sample in one end face of a cylindrical holder made 
of a suitable plastic, and the holder and sample are 
manually held in contact with the abrasive-covered 
surface of the rotating wheel of a polishing table 
until the sample acquires the desired metallographic 
surface. To obtain the required flatness, the sample 
must be counterrotated with respect to the rotation of 
the polishing wheel during polishing. As conventionally 
practiced, counterrotation of the samples is both a 
tedious and slow process. Although commercially 
available attachments eliminate such manual nro-
One such attachment is designed to fit only the manu-
facturer's special polishing tables and utilizes a pinion 
arbor and a large gear to rotate a multiple-sample 
carrier. 
The solution: 
A relatively simple, inexpensive device that can be 
attached to most metal log raphic-sample polishing 
tables has been designed. The device incorporates a 
ring which is mounted on the polishing wheel to fric-
tionally drive one or two freely rotatable sample car-
riers. A bar bridged above the polishing wheel sup-
ports two rollers which in conjunction with the ring 
confines the rotating sample carriers to the desired 
surface region of the polishing wheel and effects 
automatic polishing of the samples, without attention 
by the oneritnr excent for the 1ditinn of more 
cessing, these are both complicated and expensive.
	 ishing slurry from time to time. This depends on 
continued oerIe,ti 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19690000551 2020-03-16T18:26:33+00:00Z
the speed of the polishing wheel, which should not 
be more than about 500 rpm. 
How its done: 
Figure I shows the automatic sample rotator in-
stalled on a conventional polishing table. This table 
includes a flat disk or polishing wheel which is 
mounted for rotation in a horizontal plane on the 
spindle of a variable-speed motor. The exposed face of 
the wheel is covered with a polishing cloth adapted 
to carry a finely powdered abrasive with a water or 
oil base. The cloth is normally secured to the face of 
the wheel by means of a split ring which clamps the 
edge of the cloth to the periphery of the wheel. A con-
ventional sample holder containing the sample to be 
polished is mounted in a specially designed carrier 
which is placed on the polishing cloth. As shown in 
the figure, two samples (contained in sample holders), 
mounted in carriers placed on opposite sides of the 
bar, may be processed at one time. The carriers have 
a reduced-diameter shaft extension on which a tubular 
weight may be optionally installed (as shown on the 
left side of the bar). Assuming counterclockwise 
rotation of the polishing wheel, the abrasive-loaded 
face of the cloth will urge the carriers against the roll-
ers and the inner face of the friction-drive ring. When 
the drive rings (made of resilient material) on the 
carriers come into contact with the inner face of the 
friction-drive ring, the carriers will be caused to ro-
tate in the same direction because of the frictional 
contact, the carriers being restrained by the friction-
drive ring and the rollers from travelling further with 
the polishing wheel. The journal-mounted rollers do 
not interfere with the rotation of the carriers and act
to hold the drive rings on the carriers in driving Con-
tact with the inner face of the friction-drive ring. This 
rotation of the carriers ensures that the sample faces 
will properly shift across the desired abrasive path 
during the polishing operation. A small hole in the 
carrier is provided to let out slurry that gets into the 
carrier. To release the sample, the lock nut is loosened 
and the positioning screw,
 is tightened. 
Component details of the automatic sample rotator 
are shown in figure 2 The sample holder (not shown) 
is mounted within a recess in the carrier containing a 
machined 0-ring groove in which the 0-ring is re-
tained to provide a friction fit for the sample holder. 
The carrier is also provided with two external periph-
eral grooves for the resilient drive rings and with a 
threaded axial bore (not shown) in which the sample 
holder positioning screw (with locknut) is fitted for 
adjusting the projection of the sample holder (plus 
sample) from the carrier. The bar contains two bores 
which retain bearings for the roller mounting shafts. 
These are threaded to mate with the domed nuts used 
to secure the roller mounting shafts in the bearings. 
Note: 
This Tech Brief is complete in itself. No additional 
documentation is available. 
Patent status: 
No patent action is contemplated b NASA. 
Source: J. M. Adkins and E. C. Berneit of 
Caltech/J PL 
under contract to 
NASA Pasadena Office 
(N PO- 11015) 
Bar 
Bores for Roller 
Bearings 
Domed Nut 
Sample Holder
- Positioning Screw ... ) Tubular Wei	 it 
RollerShaft 
Roller 
Bar Locking Screw Roller Bearings 
Shaft Extension Sample Carrier
0	
.	 Car r Recess 
", Locknut	 Ring, 
Tubular Weight	 External Groo 0 
Resilient Drive Rings	 0-Ring	 Friction-Drive Ring 
Brief 69-10596	 Figure 2
	 Category 03 


Automatic sample rotator for metallographic polishing

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