420 



APPLIED SCIENCE 





FIG. 198. 

 Looking 

 Down 

 Edge of 

 Rip - Saw 

 (Enlarged 

 View) 



483. The Operation of Sawing. The opera- 

 tion of sawing consists, first, in cutting the wood 

 or metal, and second, in widening the cut in 

 order that the tool may penetrate the material 

 and then allow the cutting edge to go on (Fig. 

 196). In widening the cut, the fibers must be 

 pressed apart. The force that is required to 

 carry the saw forward, when the cutting edge 

 is just entering the wood or metal, is due to the 

 resistance of the material; the larger the angle 

 of the cutting edge, that is, the greater the 

 difference in direction between the stock and the 

 cutting tool, the more abrupt will be the turning 

 of the shaving or the chip of the metal, and 

 consequently the greater the resistance to sawing. 

 Experienced mechanics know that the smaller 

 the angle of the cutting tool that the metal or 

 wood will allow without breaking the tool, the 

 easier it is for the worker. 



484. Action of a Rip-Saw. The object of a 

 rip-saw is to cut or saw lumber lengthwise with 

 the grain. This type of saw has a different tooth 

 action from that of the cross-cut saw. The tooth 

 of the rip-saw (Fig. 197) has a straight front, 

 and its cutting edge strikes (Fig. 198) the fiber 

 of the wood at an angle of about 90. It sepa- 

 rates the fiber at one place only and the front 

 of the tooth wedges out the piece of wood. This 

 form of tooth does not sever the fibers because 

 the line of the cutting edge runs lengthwise with 

 the fiber, instead of across it. The saw does not 



