48 THE MEASUREMENT OF LOGS— BOARD-FOOT CONTENTS 



Saw Kerf. The fewer the number of saw cuts required, the less the 

 waste. Lumber sawed and measured to standard thicknesses greater 

 than 1 inch therefore increases the total output in board feet. A dimin- 

 ished thickness of the saw has a similar influence. Log rules, correct 

 when adapted to a j-inch saw kerf, give an over-run of more than 10 

 per cent when a |-inch saw kerf is cut. The use of circular saws cutting 

 a 3^-inch kerf partially accounts for the small scaled contents given 

 by some of the old log rules. 



Slabs. Waste in slabs is reduced by sawing narrow and thin boards 

 and short lengths. The short lengths serve to fully utilize the taper in 

 long logs, increasing the over-run on this class of material. The method 

 of sawing a log also affects the per cent of utilization of slabs. Slash 

 sawing, or sawing alive, as practiced for round-edged boards (§ 21) 

 would result in waste where the boards are to be used in their full length, 

 and trimmed to square parallel edges. By this method, short boards 

 would be secured from but two sides of the log. The usual custom in 

 manufacturing lumber of standard lengths is to turn and square the log, 

 slabbing all four sides. 



The gain in sawed product, by sawing around, in comparison with slash sawing, 

 for square-edged boards, was shown to equal the following per cents, as determined 

 by H. D. Tiemann. 



TABLE VI 



Gain in Output Secured by Sawing Around, Compared with Slash Sawing, 

 IN Per Cent of Latter Output 



Above 13 inches the difference is less perceptible. Where round-edged boards 

 are fully utilized and not reduced to square parallel edges, not only does sawing 

 around give place to slash sawing, but the per cent of utilization is much greater 

 than by either method of sawing for square-edged lumber, due to the shorter lengths 

 utilized in working up the round-edged lumber in the factory. 



