WOODC UTTERS IM L^LEMEXTS. 



209 



S9t should never be more than double the width of the blade at 

 the base of the teeth. 



Kecently in America saws have been much used with per- 



FiG. 94. Fig. 95. 



manently set teeth, their thickness behig greater than the blade 

 of the saw. 



The action of sawing is furthermore aftected by the resistance of 

 the different woods : this is greater in large pieces than in smaller 



Fig. 



(After Fenuuulez. ) 



'""■"''^^i^'^i^yy^. 



ones and for trees with knots than for even-grained wood ; the 

 degrees of resistance offered by woods of different species of trees 

 to sawing have been already given (p. 37). 



The measure of the work done by a saw is the surface sawn 



Fio. 9". (After Fernandez.) 



Wedge ■ 



per minute, measured in square feet ; a good cast-steel saw will 

 frequently do three times the work of inferior saws, and will 

 thus save labour considerably. 



[Pit-saws (fig. 96) for longitudinal sawing are not so much used 



VOL. V. p 



