System for testing bolts with various platings, lubricants, nuts, and tightening procedures tests 200 fasteners, and processes and summarizes the results, within one month. System measures input torque, nut rotation, bolt clamping force, bolt shank twist, and bolt elongation, data is printed in report form. Test apparatus is described

Carlucci, J., Jr.

Lobb, V. B.

Stoller, F. W.

English

NASA Technical Reports Server

December 1970
	 Brief 70-100' 
NASA TECH BRIEF 
C* 
NASA Tech Briefs announce new 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 progam may be directed to the Tech-
nology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Automatic, Computerized Testing of Bolts 
Figure 1 Test-Apparatus Bolt Clamp 
A novel computerized system for testing bolts with 
various platings, lubricants, nuts, and tightening 
procedures produces five rows of data, printed in 
report form, more rapidly than three are produced by 
older systems. 
Most commercial bolt-testers are hydraulic, with 
limited, visual readout. The nuts must be turned and 
the turns marked b y
 hand. The purpose in developing 
this riCV . automatic, computerized system (Fig. 1
was to determine the best combination of plating, 
lubrication, nut type, and tightening procedure for 
both a reliably tensioned fastener and an identifiable 
and reproducible level of tension. With this system, 
200 fasteners can be tested, and the results processed 
and summarized, within one month. The bolt elonga-
tion and the shank torque are measured, and the data 
is delivered in the form of a printed report. 
The five characteristics selected for measurement 
(continued oenieaf) 
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=19700000637 2020-03-17T01:00:41+00:00Z
I 
Fig. 2. Close-Up to the Apparatus Pickoff 
are: (I) input torque and (2) nut rotation (to determine 
their relationship to the bolt clamping force); (3) bolt 
clamping force (the basis of the study): (4) bolt shank 
twist (to evaluate the torsion variations with different 
platings and lubricants): and (5) bolt elongation (to 
evaluate its relationship to clamping force). 
The test apparatus is comprised of an input-torque 
multiplying device and an instrumented data-pickoff 
fixture (Fig. 2). The torque multiplier consists of a 
worm shaft and gear, with a ratio motor. The fixture 
holds the head of the bolt and allows the nut to be 
turned without interfering with the pickoff. 
Input torque is measured by a strain-gage bridge 
fixed to the input shaft of the fixture. The number 
of partial rotations of the nut is measured by a ten-
turn potentiometer driven by the input shaft. Clamp-
ing force is measured by a Lockheed force washer 
installed in a fixture holding the bolt head. Bolt 
twist is measured by a strain-gage beam mounted on 
the fixture, and deflected by a cam mounted on a 
threaded shaft. The threads engage the end of the bolt 
that protrudes through the nut. Bolt elongation is 
measured by a strain-gage beam deflection caused by 
the linear motion of the threaded shaft.
All transducer signals are fed into bridge-supply/ 
bridge-completion modules and then to dc amplifiers. 
Amplifier signals are fed through a multiconductor 
data link to a computer. The data are compiled, and 
stress and strain calculations are typed in report form. 
Visual analog recorders furnish continuous data read-
out for real-time checking during the tests, or for later 
back-checking. 
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: TSP70-10657 
Patent status: 
No patent action is contemplated by NASA. 
Source: V. B. Lobb, F. W. Stoller, 
and J. Carlucci, Jr., of 
Caltech/JPL 
under contract to 
NASA Pasadena Office 
(N PO- l 1090) 
Brief 70-10657	 Category 06


Automatic, computerized testing of bolts

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