Metal Working Finishing 65 



To prevent injury to the first thread while cutting the second, 

 the stud is held by a nut of its own size, which has been cut 

 into two pieces, and clamped in a vice, the width of the saw cut 

 providing sufficient space to secure a tight hold. 



Studs are screwed home by screwing a nut down upon the 

 top thread, and a second nut down upon that, backing the first 

 one slightly upon the second when they touch. By this means 

 the two nuts become " locked/' and the spanner will not move 

 either until the stud is screwed home. By putting a spanner 

 upon each nut, and pulling in opposite directions, these may 

 then be separated and removed. 



In any position where vibration is great, all nuts should be 

 locked by a second when screwed home. This is better than 

 drilling the bolt and putting a split pin through above the nut, as 

 this simply prevents the nut from falling off, not from " slacking." 

 Many good locking devices are now upon the market, split 

 spring-washers, castelled nuts 1 and split hexagonal trough 

 washers, set screws, and many other equally serviceable and 

 ingenious arrangements, developed mainly by the growth of 

 autolocomotion, but this is not the place for a lengthy discussion 

 of such devices. The second lock nut, or a castelled nut and 

 split pin will be found to answer practically all the purposes 

 desired by instrument makers. 



V. FINISHING OF METAL WORK. 



The finishing of a piece of filed work is important. From 

 the file the material is left with its surface more or less roughly 

 scratched ; this is to be removed. The removal is accomplished 

 by the use of progressively finer files in trueing up the surfaces, 

 the last file leaving a perfectly plane surface. To secure 



1 In the castelled nut, a hole is certainly drilled through the bolt, but the 

 top of the nut projects, and has three slots cut across it, into any of which 

 the split pin may go, and as the nut is slotted for about three threads, the 

 single split pin locks the nuts for a considerable number of points. Should 

 the nut proceed up the thread in the course of time, sufficiently to render the 

 split pin ineffective, an extra washer is slipped under the nut, and this 

 restores the device to usefulness. 



