Metal Working Tools 



39 



cut more quickly and give better clearance for waste ; but as 

 they break very easily, being generally over hardened, they are 



FIG. 28. Breast drill. 



more expensive in the long run. Cases of drills are obtain- 

 able from any tool maker accustomed to supply jewellers 

 with tools. 



FIG. 29. Horizontal hand drill. 



Jewellers' Turn Screw. This is a "screwdriver" with 

 loose top, and is held and used as shown in Fig. 30. It is a 

 very necessary tool for taking down scientific instruments. 

 Bits are provided for each size of screw head, and this saves 

 much trouble and a good deal of damage to delicate 

 screws. 



