50 THE MEASUREMENT OF LOGS— BOARD-FOOT CONTENTS 



Variable Standards. As contrasted with these fixed standard rules, 

 comes the suggestion ' for a log rule in which average thickness of lumber, 

 saw kerf and degree of utilization of slabs and taper shall be represented 

 by variable quantities, and adjusted by each mill owner to suit the 

 conditions of manufacture prevailing at the time or for the past few 

 months. Such a rule, when adjusted, would eliminate over-run as 

 long as the variables in manufacture on which it was computed remained 

 unchanged. But as a standard of measurement it could never have 

 any general or legal status unless its values were fixed, when it would 

 at once be open to the same objections which by its flexibility it sought 

 to avoid. 



50. The Need for More Accurate Log Rules. The great question 

 with log rules is whether conditions have changed so permanently that 

 new rules adjusted to these factors should replace those now in use. 

 The j-inch circular saw is still retained in small custom mills, and there 

 is a tendency, in regions that have been cut over by big operators, to 

 revert to these primitive methods. The operator of a band saw mill 

 is probably entitled to the over-run resulting from the use of thinner 

 saws and closer utilization. A log rule made to scale closely the out- 

 put of such up-to-date plants would exceed the product of the small 

 mill. Provided the rule is consistent, a conservative log rule which 

 will give an over-run varying in per cent with closeness of utilization 

 is probably better for commercial uses than one which aims at securing 

 the maximum product from modern mills. 



Log rules based on correct mathematical principles are the only 

 rules from which consistent and satisfactory results can be expected, 

 and this is a far more important factor than the elimination of over- 

 run. If, in addition, such log rules conform to the present conditions 

 of manufacture, they have a use in scientific measurements of logs and 

 standing timber, as a basis for estimates of volume and growth expressed 

 in the board-foot unit. This use of such a rule would justify its exist- 

 ence, entirely aside from the question of its possible universal adoption 

 as a legal standard of log measure. 



51. The Waste from Slabs and Edgings. The total waste in sawing 

 straight sound logs is the sum of the two factors, sawdust, and slabs 

 plus edgings. For lumber of a given thickness, such as 1-inch boards, 

 the portion of the cross section of the log wasted in slabs and edgings 

 may be shown graphically by plotting on diagrams, allowing the proper 

 space between each board for saw kerf. From these diagrams it is 

 possible to compute the area of this waste, in square inches, and the 

 thickness of a ring or collar which will have the same area and thus 

 represent the waste from slabbing and edging. 



1 H. E. McKenzie, Bui. 5, California State Board of Forestry, 1915. 



