•OS 



FKLLINO AND C'ONVEKSION. 



Saws are set in order that tlif blade may be easily drawn 

 backwards and forwards in the wood Avithout buckling ; this is 

 effected by forcing over the successive teeth alternately to the 

 right and left of the axis of the blade. In order that setting 

 may be properly effected, the metal must be sufficiently soft for 

 the teeth to bend without breaking, but the blade must not be 

 too soft, or the teeth will retain neither their edge nor their set. 



By use, the teeth lose their sharpness and come back into 

 their original position. The chief excellence of cast-steel saws 

 consists in the fact that they retain their edge and set much 



Fig. 9 



better than old-fashioned saws. If any of the teeth are too hard 

 they can be softened by holding them for a few seconds between 

 a pair of red-hot pincers. For setting th;; teeth of saws a key, 

 usually of the shape shown in tig. 92, is used, the teeth being 

 held in one of the grooves, and then bent-over. Fig. 93 is a 

 mechanical apparatus for setting the teetli of saws in a very 

 regular manner. The blade in n (shewn in section) rests on 

 the adjustable screw dp, which may be raised or lowered, and 

 on the anvil <> o, so that the teeth pass successively between <i a, 

 and are bent by the hammer A". The apparatus is tirmly fixed to 

 a solid basis by the spike c 



Figs. 94 and 95 represent other mechanical saw-sets; in both 

 of them a is a bar which drives the teeth into position. 



A wider set is usual with softwoods than with hardwoods, 

 and long saws also require a wider set than short ones. The 



