Machine was developed to finish ball to roundness within 12.5 nm (half a microinch) from any types of hard material. Grinding and polishing to this tolerance is accomplished by lapping elements on four to six motor-driven spindles. Spindles are adjustably spring-loaded to ensure constant contact pressure on ball and are driven by variable speed electric motors

Angele, W.

Hill, J. P., Jr.

English

NASA Technical Reports Server

September 1972
	
1372-10595 
NASA TECH BRIEF 
iJui sk all Spa ce Flight Center 
NASA Tech Briefs announce now technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Machine Finishes Balls to High Degree of Roundness 
The machine shown in the figure will finish a ball to 
roundness (sphericity) within 12.5 nm (half a microinch) 
from any type of hard material. Machines used previously 
would produce a ball with accuracy of only 125 nm 
(five microinches) roundness. Grinding and polishing of 
the ball to this tolerance are accomplished by lapping 
elements on four to six motor-driven spindles. 
Four spindles with lapping elements used for grinding 
and polishing a relatively small ball are positioned 
around a circular opening in an aluminum platform 
which is supported by one solid-metal side and two leg 
brackets on the opposite corners. The spindles holding 
the polishing laps are adjustably spring-loaded to ensure 
constant contact piessure on the hail and arc driven h
tour electric motors mounted on the platform. Individual 
motor controls are mounted on the side of the platform 
and allow variation of the speed and direction of 
spindle rotation, which results in a random motion of 
the ball. It is this random motion with respect to the 
polishing laps that effects the high degree of uniform 
roundness in the ball. 
The grinding-lapping compound drips onto the ball 
from a container positioned directly overhead (not 
shown). The excess compound and the abraded ball 
particles are collected in a container below the opening 
in the platform. For a heavier and larger diameter ball, 
a fifth spindle is used to support the hail froin below: 
ilik	 ptiidlc i	 dmicn h	 am: cicciiic flour iioimuitcd iii: 
This document was prepared under the sponsorship of the National
	
Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States
	
information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States
	
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19720000594 2020-03-17T03:37:04+00:00Z
an angle arm beneath the platform. When the fifth 
spindle is used, a ring channel beneath the spindle 
catches the compound and material removed from the 
ball, thus preventing coating and clogging of the motor. 
A sixth spindle and motor may be mounted directly 
over the ball to provide a faster finishing rate and 
improved roundness.
Patent status: 
Inquiries concerning rights for the commercial use 
of this invention should be addressed to: 
Patent Counsel 
Marshall Space Flight Center 
Code A&PS-PAT 
Marshall Space Flight Center, Alabama 35812 
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Code A&PS-TU 
Marshall Space Flight Center, Alabama 35812 
Reference: B72-10595
Source: W. Angele and J. P. Hill, Jr.

Marshall Space Flight Center

(MFS-21 448) 
B72-10595	 Category 08


Machine finishes balls to high degree of roundness

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