52 STATE BOARD OF FORESTRY. 



factor is correct for a gang saw with saws k" thick and V apart, but 

 does not apply to any other milling conditions. Taper is not taken into 

 consideration by either of these rules. Both rules have a fixed slab 

 allowance, and the sawdust factor is affected by saw-kerf alone. 



The International Log Rule also has a fixed slab allowance, and the 

 sawdust allowance is unaffected by the dimensions of the lumber to be 

 sawed. The value of this factor has been worked out for different gauge 

 saws, and is the same regardless of dimensions of the manufactured 

 product. The rule has a fixed taper allowance of \" in 4', and tables 

 compiled in accordance with the rule are based upon 4' sections. 



Since the analysis proved that no log rule now in use is universally 

 applicable, a rule has been prepared and designated the McKenzie rule, 

 which may be made to apply accurately to any set of conditions and at 

 all times be susceptible to proper corrections made necessary by modi- 

 fications of local methods employed. 



This rule, with no allowance made for shrinkage and surfacing, is 

 shown on page 19, and for convenience may be written : 



k) (t + k) - 



4X12 



With an allowance for shrinkage and surfacing included, the rule 

 complete becomes : 



17- '-L+C=KM. 



I (ic + c + k) (t-\-6 + k) J 4X12 



Where 5 and c in inches, represent these allowances in thickness and 

 width, respectively. 



