68 FOREST UTILIZATION 



Thirty-two teeth, cutting 1-32 inch each 

 at a revolution. 



The number of teeth for one inch of feed 

 should be, in hard timber, 16 teeth ; in 

 medium timber, 12 teeth, and in soft 

 timber, 8 teeth. 



The usual feed is from I to 6 inches per 

 revolution. The quicker the feed the 

 more teeth are required to do the work. 



3. The saw must be perpendicularly hung ; 



must slip on the mandrel against the fast 

 collar easily, so as not to twist the saw 

 out of true, thus causing it to buckle 

 when the loose collar is tightened up. 



The loose collar is hollow at the center 

 (small saws excepted) and has about 6 

 inches diameter and ^ inch rim. 



By pressing a layer of writing paper be- 

 tween the collar and the saw the saw 

 may be slightly bent toward or away 

 from the carriage. 



4. The saw must be evenly set (either spring 



or swage set). The teeth, filed square 

 (not to a point but to a cutting edge), 

 must form an exact circle and must re- 

 tain that form in the course of operation. 



5. The teeth must have the proper pitch. 



A shallow tooth cuts the smoothest lum- 

 ber, but forbids of rapid feeding. 



The modern shape of teeth is such as will 

 facilitate filing and as will preserve the 

 original pitch. 



A tooth gets dull over as much of an inch 

 as it cuts. 



The gullet of the tooth must be larger for 

 soft wood than for hard wood. Large 

 gullets weaken the saw, small ones in- 

 crease the friction very badly. 



A tooth should be filed two to four times 

 a day. The backs of the teeth must 

 never protrude beyond the point. 



Gullets must be kept circular carefully. Any 

 sharp edge in a gullet is sure to cause a 

 crack. 



6. The mandrel must not heat in the jour- 



nals. The boxes require frequent rebab- 

 bitting. The stem of the mandrel must 

 be exactly level and perfectly straight. 



