Calculating Board Feet - Woodworking Talk - Woodworkers Forum

Old 01-04-2011, 08:27 PM Thread Starter
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Calculating Board Feet

Is there a simple formula for calculating total board feet in a log?

We frequently have access to fresh cut logs at work. They typically get cut up and hauled to a compost yard but we can take them if we want. Lots of guys take them for firewood. Today a guy took about 10 Walnut logs and a couple Cherry logs to mill. He has an old mill at home. I started researching local milling and found a guy that will travel to your logs and mill them to your specs for \$.50 per board foot. He calculates total board feet in the log before milling it and you pay for the total regardless of waste. I just want a formula that I can use to calculate and get a rough idea what it will cost me to mill a log. I'm having trouble finding anything local except 4/4 and I'd like to find some 6/4 and maybe even some 8/4 to play around with. \$.50 per board foot is sounding real good but I dont know how much I'm gonna be spending on waste wood.
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Old 01-04-2011, 08:35 PM
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http://www.woodweb.com/cgi-bin/calcu...tor=log_volume

I use the Doyle scale

Or print this chart off I made. I have them all over (in the shed, by the phone, in the truck...) So I can get a ballpark real quick.

This is the actual formula for calculating Doyle scale.

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Last edited by Daren; 01-04-2011 at 08:41 PM.
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Old 01-04-2011, 08:44 PM Thread Starter
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Thanks, that will be a huge help.

While I have your attention, your chart shows roughly 100 board feet in a 10' log thats 16". That would be about the average size log I have available to me. In a Walnut log of that size, roughly how much of that 100 board feet is usable lumber?
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Old 01-04-2011, 08:59 PM
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...Loaded question, 100 bft can be milled out of it, "usable" is up to you. How much he wastes is dependant on his skill (I am assuming he knows how to run the mill) Since he is coming to you that says bandmill. I get about 10% overrun, meaning I can cut 10% more usually than the log scales on my bandmill. (I charge by the lumber milled doing custom milling, purchase logs for myself by the scale)

At \$0.50 bft him coming to you, it's a no brainer. You are getting free logs. Go for it, I can't see you getting hurt.

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Old 01-04-2011, 09:01 PM
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Since you're wanting to calculate in the field the easiest way is to carry a chart card. Most of them have Doyle, Scribner, and International scales. Eastern Red Cedar has its own scale to allow for the excessive waste iin that species.

I guess you can also figure it by averaging the diameter of top and butt and then using the formula for calculating the volume of a cylinder, which is pi x r² x l. Or 3.14 times the radius times the radius, times the length.

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Old 01-04-2011, 09:04 PM
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Dayum. Y'all had a whole conversation while I was typing my answer between tasks. When I started it there were not even any views much less posts. Speedy Gonzales here.

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Old 01-04-2011, 09:16 PM Thread Starter
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Thanks for the help guys!!

Daren, when I start getting my own logs milled, I'll be ordering your kiln plans.

Last question...Sometimes I may only be able to get 1 log where other times I may be able to get several. Would a cut log laying outside for a few weeks without being milled hurt anything? I imagine I would wait till I had several before haveing him drag his equipment over.
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Old 01-04-2011, 09:21 PM
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This time of year they can lay totally unchanged until ~April here in the midwest. You need to seal the ends. I use anchorseal, in a pinch 2-3 coats of exterior latex paint will work. Having said that I have walnut logs in the yard that are 2+ years old...still as good at the day they were felled (the heartwood anyway, all I care about). Keep them up off the ground/in the shade/seal the ends=no problems.

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Old 01-04-2011, 09:33 PM Thread Starter
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Thanks alot. You have convinced me to start carrying logs home. I'm sure the wife will be thrilled. Wait till she finds out I'm gonna build a kiln behind the garage where her garden is!!
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Old 01-04-2011, 11:02 PM
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Daren,
you have provided a great deal of knowledge and information over the years. And all is much appreciated but I do have a question or two. You mention the formula. When I compute this the numbers come out far less. Am I missing something? Or does this assume the loss of diameter at the fat end? Inquiry minds want to know.

10" log - 4 = 6/4 = 1.5 squared equels 2.25 x 6' length nets out 13.5 not 20.

on the high end
26" log - 4 = 22/4 =5.4 squared equals 29.16 x 16' = 466.56
you have 500.

Is the yeild rough sawn? if so can I expect a 33% loss on smaller logs up to a 7% loss on larger? The differance seams to be misleading. just wondering why? Just trying to understand the scale for practical use. I thank you in advance for your reply.
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Old 01-04-2011, 11:54 PM
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Quote:
Originally Posted by mdeiley View Post
Am I missing something?
Quote:
Originally Posted by Daren View Post
So I can get a ballpark real quick.
I gave the formula (for Doyle, the scale I use, there are several others) and a chart. Given the time to work the math on a specific transaction/per log, well you understand the proven formula...Facing a semi trailer load of logs that I have to shoot a fair price at or it leaves in ten minutes, I use the chart.

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Old 01-05-2011, 01:24 AM
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I agree, the formula or the chart is incorrect unless the chart has the bandsaw kerf savings calculated in. Most scales were set up for circular saws with larger kerf/loss = footage.
I Have a log rule that has the doyle scale on the back. No extra charts to keep up with !!!!!!! My understanding these rules can be bought with the scale of your desire. It has been a few years (15) since purchase. Time flies when your having fun !!!!!!
Have a Blessed day,
Tim
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Old 01-05-2011, 10:57 AM
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Quote:
Originally Posted by mdeiley View Post
Just trying to understand the scale for practical use.
In the real world we have to ballpark it most of the time, that is the only thing practial. Here is more reading on the subject. It goes over the 3 most common log scales (Doyle, Scribner, International 1/4 inch) Way too much reading on other variations on the log rules. And these rules are all effected by cull, or log defects.

To boil it all down a guy has to pick a scale and stick to it in his dealings. A few bft one direction or the other when scaling all averages out in the end anyway on the mill. These scales were established (MANY years ago) basically so all parties in a transaction are working by the same "rule" or way of doing the math.

As not to get too technical and take away from the original question "Is there a simple formula for calculating total board feet in a log?" ...yes about 20 ...I use my chart on the fly, the calculator I linked if I am sitting at the computer...But what comes off the mill is never exactly what either says, they are ballparks. @ \$0.50 bft total investment (on any scale) for custom sawn walnut is a good deal. Walnut sawlogs as a raw material cost that (or more).

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