Doyle scale basics

A primer for those unfamiliar with the Doyle scale. March 28, 2001

Q.
Does the Doyle scale allow for saw kerf? Does it allow for a certain percentage waste as pith or does it assume "boxed heart" lumber? If I wanted 1000 BF total finished lumber, how much should my overage be, using the Doyle scale (cut 10 % more per the scale)?

Forum Responses
The Doyle scale, like most scales, estimates the lumber you can get from a log. Therefore, saw kerf is considered. However, the Doyle scale has an added feature--for smaller logs it under-estimates the actual volume you will recover. So, it may estimate 100 BF, but you will actually achieve 140 BF. With thinner kerf, you will get slightly more than with a thick kerf--about 4% more, unless you use a really thin kerf. Of course, the excessive opening face size and over-edging will waste even more than a thicker kerf.

Why does Doyle do this? The idea today is that smaller logs cost more to handle, so rather than subtract from the actual footage (Int. 1/4 inch scale), and possibly make the logger upset (or pay less for smaller logs), the Doyle scale automatically covers the extra handling cost.

Gene Wengert, forum technical advisor

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I felt Doyle was a rip-off for the timber owner. On my little circular mill, I can normally beat Scribner by a little, Doyle is attainable with branches, and I can't seem to hit International. Is it just me or is that typical?

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You should be able to hit International every day of the year. Something is not right--are you using the small end inside bark? Are you using the length to the last foot and not rounding upward? Hardwood or softwood? What is your lumber thickness? What is the width of the first piece of lumber from each face? Are you measuring all the lumber and the cant?

Gene Wengert, forum technical advisor

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I run a small home mill (46" Timberking). I am using small end inside bark, length is right, mixed hardwood I harvest off my land (I use all of the tree possible), 4/4 and 8/4 (target 1 1/8 + 2 1/8"). I like to see about a 4-6" face. Yes, I usually can score the dog board as a usable 8/4.

I need to know how to reduce the scale for bogus logs. What should my target sizes be? What should my target 1st face be? On this mill, I have a hard time getting a small dog board (4/4 shim behind, between blocks and cant and about 3/4" bearing on carriage for last (8/4) rip, the log dogs don't seem to come close enough to the blocks).

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When you scale a log, there is the gross scale (which counts the log as straight, free of defects) and then the net scale, in which deductions are made for sweep, rot, etc. My discussion was based on net and it appears that you are talking about gross scale only. Most state forestry offices will have a brochure on log scaling and deductions.

Gene Wengert, forum technical advisor