How to scale logs

[Qweaver]

It's easy to calculate the BF in a log but how do you reduce that figure for knots, crook and other flaws?  I want to start buying logs from loggers and individuals but have no scaling skills.

[luvmexfood]

Not a lot of guidance online that I have been able to find. This one booklet from the USFS is all I have been able to find. USFS Technical Report NE-1 or NE-I. Don't have the link for it.

[Puffergas]

Use your sawing experience. If you "reduce" the scale too much suppliers might stop selling. You could have lower grades so if a log was too bad drop it to a lower grade. Loggers have to do a lot of work to put stems in your yard and they tend to like a good scale but if they are bringing junk in a lower grade might change that habit....


Good luck,

[GlennCz]

What are you buying the logs for?  What type of supplier is going to sell them to you? What type of logs?
This is an odd question, because buying logs is a highly technical skill that takes a lot of experience.
I've never bought a log, but I've sold plenty.  You need some kind of mentor to teach you this skill and oversee you while you get the experience.  You can't possibly learn it in a book or on the internet, although that would give a basic foundation.
Measuring them and getting the right size is part I, the the harder part is assigning a grade to them.   

[Reddog]

Scale doesn't get reduced for defects.

That is the object of the log grading system.

http://forest.mtu.edu/research/hwbuck/pdf/rast.pdf

[beenthere]

Scale doesn't get reduced for defects.

Reddog
I think log scale does get reduced, as it is why their is a Gross scale and, less the cull deductions, there is a Net scale.
A .pdf that may help with the deductions for cull.
https://extension.tennessee.edu/publications/Documents/PB1650.pdf

Grade of the log suggest higher or lower value per mbf by the buyer.

Qweaver
Likely you have enough experience in your sawing of logs to be able to estimate what is in a log based on the surface irregularities, bumps, voids, etc. and straightness of a log. But likely it won't be in the discussion with a logger as to what you will have to pay for the logs.

I'd suggest finding a logger, and talk with them about your interests in buying logs. They may have interest in selling, and they may not. But am thinking you would be paying more than the local mill pays, as the local mill might not cotton to the fact that their log supplier is creaming logs off the top to some other buyer. Leaves them with less quality logs at their mill. (if that makes any sense).

[Jeff]

Deductions in scale come only from things like rot and sweep. Missing wood for a better way to say it, not for grade. You can't cull for knots or stain, you just put that log in a different grade scale. I used to do a lot of the scaling at the mill, mostly because I was the guy doing the sawing. I knew by looking a a crooked log or one with a big hole in it, or the side rotted out, about how much of that log did not contain lumber, and scaled accordingly.  Reddog I'd say it closer to right on this one.

[beenthere]

And I didn't include defect such as knots and stain in the cull deductions. ;)

[stavebuyer]

It's easy to calculate the BF in a log but how do you reduce that figure for knots, crook and other flaws?  I want to start buying logs from loggers and individuals but have no scaling skills.

Your really asking about log grading. The forest service uses 3 standard grades but most commercial mills have their own proprietary systems with several more grades added in. All roughly equate to the amount of clear (FAS/1F) lumber the log is expected to yield. In general practice oak logs usually require a small end diameter of 18" and 4 clear sides with no end defects(shake, rot, etc.) to get the top advertised price. Logs with no clear sides and smaller diameters will be at the low end. Everything else falls somewhere in between. A common mill price/grade list would look like this;

White Oak Prime/Super 18"+ 4 sides clear $1600mbf
White Oak #1 16"+ 4 sides clear $1200mbf
White Oak #2 14"+ 4 sides clear $1000mbf
White Oak #3 12"+ 4 sides clear $700mbf
White Oak #4 Tie/Flooring 12"+ sound $350mbf
White Oak #5 Pallet 10"+ # $250mbf

Most times the top price is only for butt cut logs. Larger diameter logs having less clear sides will drop a grade for each side having knots. 

[Ron Wenrich]

When quoting prices, its best to know what scale.  Most buyers in my area use Doyle.  When you start getting north, some buyers will use Scribner, and a few will use International.   

When I scaled, I would box out rot and deduct for volume.  If heartrot was 8x8 and 2' deep, I'd deduct 11 bf.  I wouldn't change the grade.  I would also deduct for shake if it was bad.  There's no volume in shaky wood. 

For sweep, I would figure my volume by reducing by the amount of sweep.   If you have an 18" log with 2" sweep, I'd drop it down to 16".  That's a severe drop in footage, but those logs are harder to handle.  I'd also drop the grade to a no better than a #2.  The lumber coming out of a log with sweep doesn't dry as well or grade as well.  2 sides will have you cutting into the heart sooner than on a straight log. 

Grade is always a subjective call.  Although stavebuyer is showing 4 clear sides on all his white oak, mills in my area will allow knots in their lower grades.  Some mills will allow more knots in longer logs and maintain the grade.  A knot or two shouldn't effect the lumber grade to much if the sawyer knows how to position logs.  Longer logs will give more bf in each board, which alters the number of allowable defects due to lumber grading rules.