THE WASTE FROM SAW KERF 



53 



By slabbing in the direction of KN this waste may be still further 

 reduced, since the cylinder sawed is not parallel with the axis but follows 

 the crook at the small end, and takes maximum advantage of taper at 

 butt. Logs so crooked that their sawed contents is materially reduced 

 are not scaled " straight and sound " or full. Deductions for crook are 

 discussed in § 93. The waste from normal crook is included with that 

 for slabbing and edging and is in proportion to surface, and hence to 

 diameter. 



53. The Waste from Saw Kerf. The total waste in sawdust, unlike 

 that in slabs and edgings, takes approximately the same per cent of the 

 cubic volume of all logs, regardless of their size. If a log is sawed by the 

 method called slash sawing, in parallel saw cuts without squaring it, 

 then, after the first slab is removed, there will be one saw kerf to each 



Fig. 8. — Waste incurred as slabs and sawdust in sawing round, straight logs. 



board. The initial saw kerf, and the sawdust wasted in edging, and in 

 ripping wide boards into narrower boards, forms an additional percentage 

 of waste not exactly proportional to volume. Disregarding this dis- 

 crepancy, the fixed per cent of waste from saw kerf for the log is the same 

 as the per cent wasted in sawing one board. If the thickness of board 

 plus that of the saw is taken as 100 per cent, this waste, for a 1-inch 

 board with j-inch saw kerf is as ^ to 1 j or 20 per cent, while for a |-inch 

 saw kerf the proportion is | to 1| or 11.1 per cent. A general formula 

 applicable to saws of all thicknesses is as follows : 



Let K = width of saw kerf; 

 T = thickness of lumber. 



Then 



T+-K^ = total volume of board plus kerf, 



