Metal Working Exercises 47 



In making nuts, the hole should be drilled and the thread 

 cut before any of the metal is removed to form the well-known 

 hexagon, by which means an accurate centre is ensured. Nuts 

 may be then cut by screwing two drilled and threaded discs 

 tightly together (turning one disc slightly backwards) on a 

 threaded rod, by which means they become " locked " and can 

 be dealt with as a solid piece without risk of injury to the thread. 



In cutting threads upon rods by means of stocks and dies, 

 it should be noted that the dies being movable, a full thread is 

 never cut at once; the dies are moved apart sufficiently to 

 allow them to comfortably encompass the rod to be threaded, 

 and are gradually closed in as cutting proceeds. The test of 

 completeness is the absence of a " flat " on the outer edge of 

 the thread. This looks like two parallel lines at first which 

 come closer as cutting proceeds, and the thread is complete 

 when these disappear. 



In all cutting of threads, a liberal supply of oil should be 

 made use of, and dies should be kept well oiled and cleaned, 

 even while put away. 



In no case should thread-cutting tools be used upon steel 

 unless it has been softened or annealed, and it is better to 

 re-soften and make sure, than to use the dies on steel too hard 

 for them, which of course ruins the dies. 



III. EXERCISES IN METAL WORK. 



(i) Jointing of Wires. (A) Uninsulated. It is frequently 

 necessary to repair a broken wire, and the method adopted 

 depends largely upon the nature of the break. If plenty of wire 

 remains and one has facility for twisting, the first method will be 

 easy and successful, but if the wire be of fixed length, and unable 

 to be either twisted or half lapped, it will be necessary to employ 

 some such method as No. 4. 



Again, soldering may be impossible in some cases, consequently 

 one may be driven to various expedients which will readily enough 

 suggest themselves upon the presentation of the special problem. 

 Consequently it is not intended that this list should exhaust the 

 possibilities rather that it should suggest standard methods, from 

 which departures may be made as the exigencies of space and 

 material demand. 



