Can someone suggest a rule for projecting yield when looking at a log. My example: a 24" diameter x 10 ft. long log. I know there are many variables, but assuming it is a perfect log (straight, no embedded metal, etc.) and will be cut to yield the most material in a combination of thicknesses, what range of board foot can I expect?" Thanks, Tony O

It will depend on what grade your shooting for and thickness will impact your yield dramatically. If your customers want 4 sides heart wood only (high dollar) your yield will be much less and whether your sawing 4, 5, 6, 8/4 material will affect your yield as well.

I would cut whatever your standard scale is by 30-40% if your shooting for all dead clean heart wood and you may still come up short.

One of my mill guys just gave me the formula I'm looking for:
[(diameter of log inside bark) -4] squared, divided by 16 = bf per foot length of log.

So, per my op example:

24 - 4 = 20 squared = 400 divided by 16 = 25 bf per linear ft. of log.
So my 10 ft log could yield 250 board ft. of lumber at best.

For what it's worth, he pointed out that any tree that's near a roadway is likely to have some steel in it (signs, nails, bullets, etc.) and he always factors in the cost of broken or damaged band saw blades.

PS,. you can not "factor" the cost of metal in a log. You can have a log with one spike in it that you find either with your blade or a metal detector or you can have a log thats littered with metal. You cant apply a "factor". If you hit a nail every 12" thats 9 blades per pass you've lost. If you have to dig them out, it better be a money maker log because thats all wasted time.

There is no "factor" for metal in logs. Most people who saw logs regularly simply reject yard/urban tree's by default unless they are super juicy and totally free. At that point they are metal detector/scanning the logs and anything that comes out of those logs must be sold at a high premium due to the labor involved.

The best log rule is the 1/4 internal log rule. It assumes straight logs. It assumes 1/4” kerf.it assumes no rot or decay. It assumes no cracks, splits, or other damage.

The actual yield you achieve depends on the thickness (nominal size, like 5/4, as well as the over thickness, such as 1/8” thicker than nominal) of the lumber you are cutting. It depends on your kerf…1/8” kerf will result in about 10%increase. If you find it, the 1/8” International is best for thin band saws.

Gene,
In your experience, how does that scale (or any scale) convert to Walnut as compared to other more standard species with thinner/more typical sap? My experience was always 30% or more depending on thickness being sawn and pretty much all heart. I know no one commercially is sawing all heart but...

I use a bandsaw mill and my yields are consistently in close agreement with the Int'l 1/4" scale. If you have a log that is 24" diameter on the small end, inside the bark, that scale says there is 255 BF in it. If you have a walnut log and only want heart wood then measure the average diameter of the heartwood on the small end of the log. Let's say that same log has 2" of sapwood, so the diameter of the heart wood will be 20". The Int'l 1/4" scale says there will be 175 bf.

John