The Use of Jigs and Fixtures 



Bv S. H. Samuels 



THE average person conceives of 

 "tools" as drills, taps, reamers, 

 etc., but modern automatic ma- 

 chinery has necessitated the use of jigs 

 and fixtures for reproduction work. In 



jigs and fixtures would be unpractical 

 and extravagant. When large quantities 

 are to be produced and sent upon the 

 market, however, the results are sur- 

 prising. The cost is reduced from 50 



Fig. 3 



shop talk, they also come under the 

 listing of tools. 



Jigs and fixtures are mechanical con- 

 trivances, such that any mechanical or 

 electrical machine part may be placed 

 and held rigidly, during the process of 

 machining. Opinions vary on the exact 

 distinction to be made between the jig 

 and fixture. 



Appliances designed for use on a drill 

 press are called jigs, while those designed 

 for use on other machine tools such as 

 millers, planers, etc., are correctly called 

 fixtures. 



Jigs may be employed fur drilling, 

 reaming, centering, tapping, etc., iiU 

 these operations being done on the drill- 

 press type of machine. The fixture is 

 used in milling, turning, broaching, 

 boring, tiuicking, planing, proliiing, 

 cam-cutting, gear-cutting, and many 

 other operations in nuuiiine sh<)i)s. 



Jigs and fixtures have two distinct 

 advantages— cheapness and interchange- 

 ability of parts. When a small number 

 of machines arc to l)e built, the use of 



Fig. 6 



to 75 per cent, due to less "tooling up" 

 than would be necessan,- with separate 

 parts. . . 



This reduction in cost is attributed 

 to the fact that unskilled, low-priced 

 workmen may be empUned to operate 

 these jigs and fixtures with the same 

 amount of accuracy and rapidity that 

 the well-trained, skilful machinist would 

 do. In fact, the unskilled apprentice, 

 with the use of jigs and fixtures, can 

 accomplish more work, proportionately, 

 than the high-priced machinist, who 

 recpiires a considerable amount of time 

 to .set up the work, measuring accurately 

 e\ery dimension called for by the 

 requirements. Without any doubt, jigs 

 and fixtures eliminate brain work and 

 consequently make machine work purely 

 manual labor. 



Since cheaji labor is used in operating 

 them, jigs and fixtures must be made 

 "fool-proof," thai is, they must have no 

 comiilicattMl nu'( h.inism^ unlamihar to 

 the workni.in. I'o be well designed they 

 must not i>e "trappy." Interchange- 



474 



