Scribner - 48% Overrun

[Firebass]

I thought this was a interesting subject:

When I first started cutting lumber on my mill I was cutting red fir full sized dimensional lumber. But After driving about a keg of 20 penny galvanized nails and no hangers to match it convinced  me to saw at just over finished lumber sizes.   Recently I cut some 2x6's and realized that I can get a 48% overrun using 1/4" Kerf swing blade.   It made me wonder if accuracy is the main issue that maybe comes to play with worn out saw or such.  Or is it that wood shrinkage could be so high that a 2" board could shrink down to 1 1/2".  Or is a rough cut board more sceptical to fire?
Is a overrun this high normal?

Firebass

[Ron Wenrich]

To start with, if you're cutting 2x material on 1 1/2", you automatically have a 25% overrun.  If you were cutting hardwoods, you would barely get that by as 6/4.  That's part of the overrrun.

The other factor is that any log scale is derived from some sort of formula.  That means that not every sized log will give the same amount of overrun.  If you are running pretty much the same sized logs, your overrun would be pretty consistent.  However, if your next run of logs is bigger or smaller than your current run, the overrun will be different.

Larger mills take the overrun into account when they are buying timber or logs.   

[brdmkr]

I don't know if you could expect to have shrinkage from 2" to 1.5", but I think loosing an 1/8" or so accross 6" is pretty common.  I saw a calculator somewhere that calculated how much shrink you could expect for a given initial moisture, final moisture, species of wood, grain orientation, and dimension.  BUT, I don't know where it is now.  It may have been in our tool box (nope, just checked)

[Radar67]

It's my understanding the nominal size is not due to poor quality equipment, rather to cover warpage, shrinkage, and defect in the lumber once it is dried. All the building material gets planed on 4 sides before it is placed in the retail market.

[Kelvin]

I think that "2x4" is something that is terminology.  I doubt any large modern computer controlled sawmill actually starts with a 2" thick piece of pine to end up with a 1 1/2" thick board.  They are pretty skimpy with their mills.  Heck they have mills now that follow the curve of a log to maximize the amount of lumber they can make with a sweepy log.  Just like the NHA says wholesale hardwood lumber needs to be 1 1/8" thick or greater its just to make sure they get a clean finshed board at 3/4" thick.  My woodmizer makes lumber that cleans up a 7/8" thick when i saw on the softwood 4/4 scale which leaves it about 1" thick.  I think they just leave room to make sure that after it goes through the planer its 1 1/2" thick and straight.  Pine is quite dry by the time you saw it, so i doubt shrinkage would be very great in a thickness of 1 1/2".  Width of 6" might shrink 1/8" in the kiln, but they don't dry them but to "s" dry for construction grade, which is about what they are after air drying at my place.
Good luck.
KP

[blueduck]

All scale stick allow the mills to get overrun, some better than others, Decimal C has been the traditional scale stick in the west for a host of years, but has given way to the international rule for export logs and shoot the big boys in these parts figgered out they can steal more scale if they pay by the ton now  just like elsewhere so the scale stick is about gone it seems at times [unless they get into some really heavy wood and then they walk it back out really fast!]

Add the the fact that the beaver mills love small logs that wont scale on any stick so they cull those and then saw them anyway then use an eased edge planer bit to further get more scale and it is no wonder why some folks buy a mill for their own timber [22 years in business after hauling 2 fantastic loads on a 2 ton truck that the mill scaled at 800 and 900 feet respectively and I could have cut out of those at least 1500 and closer to 2200 feet each load on my Mobile dimension that i did not have at the time...... but soon purchased.

If can find one take a scaling class and the information will astound you as to how the scaler  can benefit the mill and just how many defects are allowed and some never taken to keep the logger happy and bring material in..... when buying logs when i first started i used a scaler that worked at one of the big mills, the loggers could not figger out how i could give better scale than the mill he worked at for similar type and size logs [and I still got overrun, though not as much as i could have and still been legal with the state check scaler] anyhow such a class is really worth the $150 or so in taking it, the materials are nearly that value able and the ability to hire out also is an appealing factor, though i have heard of loggers threatening to take the thumb off a scaler that was a little to much for the company at times..... know one scaler that was run out of town after being chased over a log deck...... those were the good ole days eh..... now there would be lawsuits for attempted assault and a quagmire of other legal issue battles......

So yes there is overrun that is used to benefit the production beaver mills that they calaim they could not live without.... yet you and I benefit very little in smaller production capacities for not all logs overrun the same, pick up a scale stick and then a lumber calcualtor book and figger it out some snowy winter day while sipping coffe and a little irish cream for to cure your hang-all-over [if indeed you ever get those type of days as not all sawmillers drink like a sailor anymore!] it will amaze you..... the smaller the log the more the overrun, larger logs give less..... the decimal C  scale stick was developed back when the tops of tress less than 8 inches were left in the woods as they were just to small to make any prodution out of it seems...... history and trivia.... sawdust and boards..... dang I aught to scribble out a book eh?

William

[Kelvin]

Good post william.  Helpful info.  I ran into this problem just recently.  I advertised full cord firewood logs for sale and scaled them each with a certain scale (doyle maybe) that i had been using.  It takes 500 bd ft to make a cord and when i saw how little bd ft were in each of my 10" dia firewood logs i pulled out an international scale and realized they were about double.  Now my problem.  Which was i morally obligated to use?  I just got these tops when i bought the trees, so i had some investment in hauling and what not, and so i decided i know how many bd ft i can saw out of a certain size log with my woodmizer so in selling them by the bd ft i concluded they would go by the one closer to reality with my samill.  I still load about 600+ when i sell 500 so its always a big pile anyways, but people are showing up and are happy to get it so i guess thats the bottom line, but yeah, what a difference!  I guess that is why you have to agree ahead of time about what scale you are using.  $1 a bd ft for small cherry logs, could mean $.50-$1.00 in actual price at the mill.  Makes a big difference for us small guys!
KP

[Firebass]

I guess it all takes time to understand the logistics of what logs cost or what they're worth.  My neighbor wants to make me a deal on some fir logs he has in a deck.  I have no Idea what I should offer him but I do no that Douglas fir has a stumpage value here between 350 and 450 a thousand.   ???

Steve

[KnotBB]

For what it's worth!

My understanding of the use of the Scribner scall.

All scalling methods are an aproximation based on certain assumptions.  And as long as everybody agrees no problems.  But most people don't understand the assumptions and are amazed at the over run in board feet verses scaled feet.  One has to understand that those are two (repeat 2) different words.  You must look at what you get paid for a certain size log.  If a log scales different using two, or more, scaling methods, the mill is still only going to pay so much for the log.  Large mills know what their recovery rate is and what margins they need to make a profit and pay investors.

The assumptions of Scribner as I understand it are based on a 16' soft wood log with  12 inches of trim length with an average taper found in much of the western USA.  Scribner was not intended to scale hard wood logs.  It assumes the log is a cylinder of constant diameter for its entire length.  It assumes a saw kerf of 1/4" thus leaving a 1 3/4" board when cutting 2" stock.  Shrinkage wiill reduce that another 1/8" and then the board is planed to standard size + or - 1/16" to allow for manufacturing defect.  One of the few hardwood mills in Oregon pays based on Scribner not because it's a better scale but because the local timber community is based Scribner and probabely never heard of International.   

Without other consideration where the mill makes its over run is based the requirement for long(er) logs or paying less for shorter ones, using a smaller kerf saw as provided by a band blade, and tighter sawing tolerance.  In some mills they even leave out the planning and sand the boards.  Other obvious gains are had by having wane left on the board thus in effect giving them a larger diameter log.  But that's lumber grading not log scaling.  One mill I heard of was getting over 200% from their logs just making studs.  But how else can we buy lumber for $500/m when the stumpage price is as high as $500/m?

Other considerations:
If a log is culled for what ever reason and the mill still saws or peels it (for plywood?) everybody looses except the mill.   And it may be marginal for the mill if the cost to saw a poor log exceedes the gain, but at least they can put in in the proper channel for waste disposal, chips?   BLM says if a log is 50% cull the whole log is cull.  That leaves a lot of nice wood in a 40" log that was free to the mill and a cost to the logger/trucker/owner.  This is one reason the loggers bought into being paid by the ton verses by scale. 

If a log has a lot of taper no allowances are made.  Long, fast taper logs have a lot more over run.

Veneer making for plywood has little loss for the mills.

But the mills do jab all ends of the supply and market sides.  How else can they make such big donations to political causes, pay their managemt such huge wages and still pay a dividend to stock holders? 

Enough,

Steve

[beenthere]

If anyone wants some history on log rules, check out the pub'n by Frank Freese "A collection of Log rules". It is based on written explanations of each of the rules and background info on where they come from.. first time I've heard that Scribner was for softwoods, and not hardwoods...but I still have a lot to learn. 

http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr01.pdf

Knottbb has said some good points for sure.

[Ron Wenrich]

I think its more that Scribner Decimal C is used more in softwoods.  That's a West Coast scale, and isn't seen here in the East.  I know of several mills that use Scribner, just not the Decimal C.