# milling efficiency



## jimmyjames (Jul 21, 2013)

This question is for the milling folk out they're that mill a lot of lumber. When you have logs figured by the Doyle scale let's say a 24" diameter 10' long log, Doyle scale reads 240 board feet. When drawn up on paper and also figuring in the thin kirf of a band saw blade, I figure over 300 board feet, and of course that's figuring the 24" is measured where bark meets wood and on the small end of the log. What's everybody's efficiency? And of course these figures are for flat sawn. Plus Doyle scale is one of the lesser scales compared to say the Scribner scale which reads less board foot in a log but is commonly used for the softwoods for framing lumber which I'm guessing they have more waste then the hardwood mills getting every last drop of wood out of a log.


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## Kevin (Jul 21, 2013)

That's a 20% difference did you use a volume calculator that asks for a particular species because some calculators will figure an inherent waste factor, and some species have more than others even given the same taper sweep etc. Doyle uses a kerf of 5/16 (big circle mill kerf) When scaling ERC it has its own system (cedar scale) and should be used to sell logs but not buy them. Until you get used to milling and estimating waste, I suggest you use Doyle or Scribner until you understand how waste really works for a given log because D & S are very forgiving compared to 1/8 or 1/4 International. Then when you have a handle on things you can start using 1/4" International because it's going to give the most accurate estimate once you understand how to account for defects like sweep etc. but of course some guys stick with Doyle or Scribner their entire milling lives and seem to get by just fine. And of course you can use Doyle for large logs and Scribner for smaller ones - but only when buying because Scribner underestimates smaller logs.  

JMO based on my experience.


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## Kevin (Jul 21, 2013)

I'll show you how I figure sweep and taper. Let's use extreme example (easier to learn that way) and put both defects in the same log. You can scale a log in the field in your head easily once you get the concept and the concept is super simple. I don't know if this is the accepted method but what I use and have since I taught it to myself. Simple geometry. Usually a swept log just needs to be thought of in two sections but we'll use three for exaggeration purpose to learn. 

http://i1077.Rule #2/albums/w468/WoodBarter/sweep1_zps8d9a6c1d.jpg


Mentally cut log into three sections because of severe sweep and taper.

http://i1077.Rule #2/albums/w468/WoodBarter/sweep2_zps3931517f.jpg

Probably no explanation needed but just in case Log section 1 = L1 etc. 

Extra wood of side of A is canceled out by waste of B and same for other two sets C/D, E/F

Let's say each section L1, L2, L3 are all 4' in length. 

Scale sections as follows:

L1 13" X 48" 

L2 15" x 48"

L3 14.5" X 48

Has worked for me well. I'm sure there's better ways but being mostly self taught I don't know what they are. This stuff is like a buffet thogh pick and chose from everyone you learn from what you like best and what works best for you.


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## gvwp (Jul 21, 2013)

My experience is the Doyle scale figures larger logs pretty much on the money but figures small logs short. You must also keep in mind the Doyle scale was made when large circular saw blades were used so thin kerf bandsaw blades will yield more lumber. This is one of Woodmizer's marketing tools. A 12" log 8' long is 32bf on the Doyle scale, however, I get at least 40bf when sawing this size of log. A 24" log 8' long is 200bf on the Doyle scale and that's pretty close to what I get when sawing this size of log.


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## CodyC (Jul 22, 2013)

The Doyle scale assumes a 5/16" kerf and a 4" slab thickness. It tends to underestimate small log volume and overestimate large log volume.


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## lone wolf (Jul 23, 2013)

I rarely mill hardwoods and use the Doyle scale for an estimating tool for buying logs, with a thin kerf bandsaw the international 1/4' scale seems to represent the output of logs best for me. If you are quarter sawing for cabinets or rift sawing boat lumber the yield is always somewhere in between the two scales.
It may be that just keeping close track of the output that any given mill or sawyer has at the end of the day and comparing it to any of the scales might be the best way to calculate mill efficiency and productivity
Every sawmill is going to be slightly different just as every sawyer does things differently or at least their own way, comparing these variables might be difficult given the differences in sawmill capabilities and productivity indexes.
As an example if you are going to quarter saw red oak finish material with a swing mill the stationary circular and bandsaw mills will most likely produce more waste and not be as efficient while a swingmill such as a lucas or mobildimensional can breeze through the work easily. On the other hand if you are cutting large beams for a timberframe structure the stationary circular or the bandsaw mill can blow out a very large beam like 24"X 36"X 40'-0" in four cuts or passes.
With both examples being extreme it is obvious that the variables are a big part of mill efficiency.


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