TOOLS AND MATERIALS 275 



signed for small holes, while the ratchet can be used for mak- 

 ing holes of almost any size. 



248. Stock Taps and Dies. Taps and dies are useful 

 for cutting threads on bolts and for threading nuts. Pipe 

 taps and dies are not to be used for bolt work. Machine 

 screw taps can be used for tapping for screws when desired. 



249. Materials Needed. For machinery repair, it is 

 essential that there be kept on hand an assorted lot of ma- 

 chine, carriage and stove bolts with nuts and washers; an 

 assorted lot of copper and soft iron rivets; an assorted lot of 

 screws of different kinds and sizes; an assorted lot of cotter 

 keys and pieces of iron rods of different diameters; pipe and 

 pieces of strap iron for general use. 



