Large bolts and nuts are accurately tightened to structures without damaging torque stresses. There are two models of bolt installation tool. One is rigidly mounted and one is hand held. Each model includes torque-multiplier unit

Mcdougal, A. R.

Norman, R. M.

English

NASA Technical Reports Server

-	 September 1974	 B74-10164 
NASA TECH BRIEF 
NASA Pasadena Office 	 4V 
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 program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Bolt Installation Tool for Tightening Large Nuts and Bolts 
I
The problem: 
Conventional torque wrenches cannot be used to 
tighten large nuts or bolts to structures that are too 
weak to withstand the specified torque. Normally when 
a torque wrench is applied to a bolt, the torque stress 
is transmitted to the structure. As a result, weak 
structures often crack before the proper torque level is 
reached. 
The solution: 
With a new bolt installation tool, large bolts and 
nuts are accurately tightened to structures without 
damaging torque stresses. 
How it's done: 
There are two models of the bolt installation tool: 
one is rigidly mounted and the other is hand held. Each 
model includes a torque-multiplier unit.
Figure 1 shows the rigidly mounted model. In 
operation, torque provided by the torque wrench is 
applied to the bolt through a tdrque-multiplier and 
wrench socket. The torque thus generated by the 
friction between the bolt head and the top surface of 
Input From Torque

Motor 
C—)
Housing 
(Locks Gear Box to 
Boss and Washer) 
Bolt Boss of 
Attached Part 
Structure
Figure 1. Rigidly-Mounted Bolt Installation Tool
(continued over$..f) 
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 Stales
	 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=19740000164 2020-03-17T13:49:25+00:00Z
Figure 2. Hand-Held Bolt Installation Tool
the boss and the thread friction is transmitted to the 
tool housing. As a result, the only torque tj1ismitted 
to the structure is from the reduced torque of the 
torque wrench. If the hand-held reaction bar is worked 
in unison with the torque wrench, no torque is trans-
mitted to the structure. 
The hand-held model, shown in Figure 2 as applied 
to an alien-head bolt, is identical in operation. The 
housing is keyed to the washer instead of the boss. The 
washer friction with the boss is larger than the total 
bolt friction and thus will not turn on the boss. This 
model is powered by a torque motor fastened to the 
housing. The reaction torque is taken internally between 
the housing and the case of the torque motor. There 
is no external torque from the device which may be 
freely hand held. 
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: TSP74-10 164 
Patent status: 
This invention is owned by NASA, and a patent 
application has been filed. Inquiries concerning non-
exclusive or exclusive license for its commercial develop-
ment should be addressed to: 
Patent Counsel 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Source: Allan R. McDougal and 
Robert M. Norman of 
Caltech/JPL 
e	 under contract to 
NASA Pasadena Office 
(NPO-1 3059)
. 
B74-10164
	 Category 07,06


Bolt installation tool for tightening large nuts and bolts

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