Edging fresh cut lumber

[CallPete]

After cutting fresh cut lumber can you go right to the Edger machine before drying?

[Puffergas]

Yes.

[Southside]

I do it every day. Just be sure to allow for shrink / warp, etc so oversize your final target. 

[YellowHammer]

"Can you?" Sure, that's what it's designed for, edging green lumber straight off the mill.  

Do I always do it?

Depends....
Many of the cuts I make are intended to put the log stress in the curve or crook plane rather than the bow plane.  I'm intentionally sawing to get stress in the "slip" direction vs stress causing "lift". We do this as a high grade lumber supplier where bow makes a board virtually unsellable whereas for framing lumber, bow is the desired bend, not crook.  So the sawing techniques are a little different and results in a different reaction in the boards.  

So this intentionally will cause crook that must be edged out later after kiln drying  and so results in a straight, and very flat board.  

Also, for example, when quartersawing, the board will almost always crook when drying, by the nature of the way the grain is oriented. QS wood should lay flat but will almost always crook.

So pretty much all the high grade furniture wood coming out of us will either be routinely run through our straight line rip saw (SLR) which gives a guaranteed 8' glue line edge, or our custom made Baker twin blade edger, which was modified by Baker with the intention to edge green as well as kiln dried wood.  Edging dried wood can be difficult with a green board edger without some tweaks.

So the way I look at it, why edge boards twice?  I try to minimize the bark edges in the cant when sawing to square up the bark and get to cutting, which minimized but doesn't totally eliminate the bark on the initial flitches. I don't generally edge them, they have generally straight although some bark, and get stickered just like the rest of the lumber.  

When everything is dry, we go through the packs and any of the boards needing edge straightening, whether they have bark on or not, all get straightened through the edger or SLR

So instead of edging those boards twice, I only do it once.

[Peter Drouin]

You must wast a lot of wood that way YH, But at $3 to $8+ a bf you must make it up??

[YellowHammer]

No, not wasting wood edging wood twice, saving wood by only edging once.  I work too hard sawing and producing high quality kiln dried, finished boards from very expensive (sometime $500 to $750 per log) to waste anything.  Edging after kiln drying instead of edging before kiln drying can save as much as 15%.

Typical numbers for straightlinig finished lumber is 15% edge drop loss.  So if I was to buy a load of sawmill sawn hardwood, kiln dried, from a commercial mill, or developed from our mill, the kiln dried board edges will not be straight enough to use for retail sales, furniture making, or much anything else, not to mention they will be by their nature, a rough sawn edge.  So most any kiln dried board, before its ready to use or sell retail, must have the rough sawmill edge removed or straightened, and will get run through a molder, planer, or SLR.  We sell by true measure, so if I mill and edge a board to 8 inches wide green off the mill, and that board later develops a curve when kiln drying, and I have to re edge it down to 7", then I eat the loss because I milled and edged green to 8" and sold at KD 7".

At a green sawmill operation, the edge drop costs, or for that matter, the gross talley vs net tally losses are not seen, and it is eaten by the secondary processor after kiln drying.  The primary processor never sees the loss, but the secondary processor always does.

Since I am both the primary and the secondary processor, and go from green sawmill lumber to kiln dried S4S, if I can postpone my edging finishing steps until after the wood is kiln dried, and use the edger to give me finished edges, not rough edges, I prevent the waste from the first process and actually make money.

For example, walnut really pulls when the sapwood is unbalanced, and I buy logs, sometimes for as much as $6 per bdft.  So when I'm sawing, I will not edge the flitches, because the sapwood is balanced side to side, and the boards will kiln dry flat.  However, they will curve when drying, because I am intentionally sawing to make sure the stress of the log is in the slip direction, not the bow direction or plane.  So I then have two options, edge them off the mill, take as much sapwood off as possible, edging into the very expensive heartwood, kiln dry them, have the boards curve, plane them, then lose 15% straightening and cutting off the rough sawn edges a second time with the SLR or edger.  OR, I can dry them with the bark on, kiln dry them, plane them and run them through the edger only once, cutting off the heartwood and producing a sellable, finished edge, and save $$.

When we bought our edger, I called up pretty much every company out there that makes edgers, or gang rip saw and discussed the requirements I needed, i.e. the ability to edge kiln dried wood as well as green wood, and put a very straight, chip free, finished edge on the board, similar to what is produced by a SLR.  At least one company said they could not do that with their edger.  Baker said they could build me one, and they did, and its been paying off ever since.

Easy decision, do less steps, save wood, and make more money to produce the same high quality product.  Take steps to save steps.

[Peter Drouin]

I get that, My? is cutting the log to get a crook out of the lumber. and not a bow up or down and when you KD it, it will stay down, no? 

[E-Tex]

........., or our custom made Baker twin blade edger, which was modified by Baker with the intention to edge green as well as kiln dried wood.  Edging dried wood can be difficult with a green board edger without some tweaks. ...........

I mill mobile, don't use an edger, nor sell lumber.  So excuse my lack of knowledge.

Is there a difference in the edger machine itself if you plan to edge green vs kiln dried?  Blades maybe?

[scsmith42]

Robert, as always very insightful discussion and comments from you.

We've been milling similarly (in terms of preferring crook over bow), but sometimes we edge off of the mill and sometimes we don't.

We do a lot of work where we mill logs from someone's property, dry them, and then process them into flooring, T&G V-groove ceiling boards, etc for them to use in the house that they are building were the trees grew.

If I'm worried about a board crooking during the drying process, then usually I won't edge so that we can net a wider board after drying.

However, if I'm not worried about crook then we edge off of the mill (such as SYP barn siding boards), then we will edge in order to minimize waste of kiln dried material.

At the end of the day I'd prefer to take a small hit on kiln drying material that is going to be edged off, as long as it allows me to net out a wider flooring / wainscoting  / paneling board over the entire length of the board.

[moodnacreek]

Lumber should be sawn, edged and stickered all in the same day.

[Peter Drouin]

Maybe I'm not asking the question the right way. When I open a log up I'm trying to get straight boards. I know some boards will crook from side to side air or kd dried. But if the boards are sliding sideways when you're halfway through the log and get to end of the cut and your 2" off the cant from where you started. I think you're fighting your self. 
 Unless your cutting½-¼ logs all-day. Then you have a pile of bananas. 

[Peter Drouin]

Lumber should be sawn, edged and stickered all in the same day.

That's what I try to do. One side slabs one side flinch. cut the cant up pull all the lumber back and sticker.


 
I have 12" 10" 8" 6" 4" all 12' long. 

[Sixacresand]

For us who deal in green lumber, when you get down to the just right size cant and begin milling off boards and you notice the "slip direction" or "slip stress" that YH mentioned. I didn't know it had a name.  At that point, you know you are going to have some bent boards.    

For that reason, I cut my cants over sized, especially the long ones.  The next step is to edge boards on the mill, four or five at a time, on both sides to get the desired width.  It is extra work and wastes wood, but when I stack/sticker on a pallet, they are straight and parallel.  The customer is much happier vs stacking crooked lumber.  

I do tell them up front that as lumber dries, it will bend.  I suggest that we mill it wider, let it dry and bring it back to "straight Line" or edge. 

[Don P]

One name for the edge it later process is SDR, Saw, Dry, Rip. It takes a lot of stack room and I don't stick to it totally but with a log that isn't behaving well I'll sometimes stack the flitches and make the cant very healthy oversize for the rest of the boards then resize them after dry.

[YellowHammer]

E-tex, Yes, a dry board and green board edger should have a slightly different configuration, although one can be built to do both well.  For example, a rock hard kiln dried board with diagonal cup along its length, will possibly rock and not track true in a standard roller feeder, much like a cupped board will rock when initially fed into a planer.  So rubber conveyor belting works better by grabbing and stabilizing the not flat board, and Baker built me one with both a belted indeed and outfield.  Also, kiln dried wood is very hard, much harder than green, so the edger must have variable feed control, and should be slowed down to protect the teeth of the blades.  I have, in fact shattered teeth of the sawblades due to too fast a feed rate and too wide a tooth spacing in too hard a kiln dried wood. This results in too much impact load on the teeth and bang, bang, bang, little teeth.  So I also had a company design some higher tooth count blades with narrow teeth to lessen impact stress.  High horsepower is also required and better dust collection is a must because all the dried sawdust aerosolizes and flies everywhere, whereas green sawdust will fall on the ground, dry sawdust goes everywhere, including my lungs.  

Peter, we are in different markets, but you are right, if I mill a 16 foot log and it curves on the slip plane like a county road, it will have too much loss to edge out, so it will be cut into 2 eight footers and then edged.  Two 8 foot boards have the exact same value as a 16 foot board, so there is no loss of worth.  

As a matter of fact, there is a walnut mill I work with that simply won't edge 16 foot long kiln dried walnut because the edge drop losses are too high.  They will edge 8 footers.  So from a value standpoint, edge drop is an important loss, and must be traced carefully.

On the other hand, although framing lumber can be sawn for bow, instead of crook, bow in a hardwood furniture board makes it virtually worthless except if cut up into very short pieces and run for flooring, where the molder takes off enough wood to make it flat.  So significant bow in a 4/4 furniture grade board is a huge loss, unless it can be flattened by machine (one more step I would like to avoid), however, it can't be out of flat more than about 1/8" per face or it won't clean up to a 3/4" board.  

So although more than 1/8" bow in a 4/4 furniture grade board will greatly devalue it, 1/8" of edge curve in the same board is easily addressed with the edger, and only turns a 6 inch wide board into a 5 1/2" board at the worst.  

In my high grade furniture market, no one, either furniture maker nor hobbiest will buy bowed hardwood furniture boards.  Why should they?  I don't want them to.  All the other hardwood mills in this area sell twisted, curved, bowed junk.  Our kiln dried wood is flat and true, and reduces the workload of the purchaser so commands a higher price and a very loyal customer base.  

Kiln drying hardwood, (I don't do much softwood, so can't really comment on that) will rarely straighten out a log stressed and bowed board, no matter how soon out is stickered.  The stress is in the wood fibers, and unless the structure of the wood fibers is changed, the stress will remain, whether the fibers are dry or green.  In fact, in some cases where lumber has a high sapwood ratio, the boards will move slightly more when dried.  Many years ago, when I was just sawing wood without really paying attention to stress, I would cut up some beautiful stuff, sticker it with perfection, air dry it, kiln dry it, plane it, deadstack it, store it in a warehouse and come back months later, and it had as much bow as it did when it came off the mill.  So I'd put it back in the pack, come back a few months alter, and it would still be bowed.

There are some steps that can be taken with a kiln that can modify the fibers in the boards and cause them to flatten, much like boiling noodles, using high heats during the drying process can soften the wood, and much like steam bending, is actually a form of steam straightening.  I've done it in my kilns, where I took all the bowed cull boards from a bunch of kiln runs, restickered them and subjected them to high heart, high humidity and high load pressure.  About 1/2 to 2/3 rds of some load can be successfully heat straightened, but that is a very non conventional process.  So in essence, a bowed hardwood board off the mill will stay a bowed hardwood board out of the kiln.

The exception to all that is spalted wood, where the initial spoiling or the degrade of the wood fibers removes much of the stress in the logs and so the lumber will come off the mill much more behaved.

[Peter Drouin]

I think we are talking about two different things. I cut  2x2 x8' - 4x4x8' 2x8x16' out of hardwood. 
 When I open up a log and can read it I get straight lumber. With no bows or crooks most of the time. ;)  
It's all about making straight lumber with me. You're doing after the wow [fleck] I think.
Your right we are in different markets.

[jbjbuild]

Forgive a newbie question, but when say you read the log to see if it is going to bow, is there something in the grain that you see, or are you noticing that the first board cut from the cant bows up so you flip the cant 90 degrees so you will get boards with a crook instead of bow. 

[YellowHammer]

The only way true to tell if a flat board off the mill will remain flat and is stress free is to inspect them after they have been kiln dried. This is true for all types of lumber distortion, including cup, warp, bow, twist, etc.  Almost all the lumber coming off a professional, or hobby mill, should be straight and true, but that's only the initial step. It's only after it's been dried and inspected will the true sawing stresses be revealed.  

Remember, we sell high grade hardwood, and 1/8" of bow per board length devalues a board for our market.  1/8" per side.  That is not much.

This is the classic picture showing how different cuts in a log will react when drying.  They come off the sawmill mill flat, true, and straight and when dried, and this is what happens.  Although these are end grain diagrams, it also somewhat applies to the boards in the longitudinal direction, and if the stress isn't read correctly and then the cant rotated to be put in the right plane, the board can either be salvaged or is scrap.  The major defects show up after drying but were imparted during sawing.



 



A quick search in the internet shows it's a real problem:
Wood warping is a deviation from flatness in timber as a result of stresses and uneven shrinkage when dry.

Wood warping costs the wood industry in the U.S. millions of dollars per year. Straight wood boards that leave a cutting facility sometimes arrive at the store yard warped. This little understood process is finally being looked at in a serious way

Here is an example of why careful edging after kiln drying is so important.  Proper edging before or after will fix this board.

[Don P]

That end view drawing is showing drying stress related to section view only, we also deal with the length of the stick. The stick at 12:00 will bow, the one at 9:00 will crook.

Growth stress will relieve itself as you are sawing, that is the board bowing towards the bark side in flatsawn lumber or crooking towards the bark side in quartersawn. Read this as you are sawing and flip or orient the log to reduce it or put it into the plane desired.

Drying stress for one is the cupping caused by the difference in radial and tangential shrinkage. Notice on the cherry above the curve is constant, rather than it being a heartwood/sapwood problem it is really more of a tangential/radial grain orientation phenomenon. Heartwood extractives do lock up shrinkage a bit in some woods but notice the shrinkage tables don't list different shrinkage rates for heartwood vs sapwood. Drying stress is also the bowing or crook caused by lengthwise shrinkage of juvenile or reaction wood vs mature wood on opposite faces or edges.

The juvenile core is up on this piece of decking. It shrinks in length as the wood dries causing bow. It shrank enough to shear the first pair of deck screws. When that board is wet it lays back down. It has done that now for hundreds of cycles, I kind of enjoy watching it.


 

In dimensional construction lumber I'll take bow over crook because I can easily pull bow (generally flatsawn) back into line with sheathing where if I edge lumber with crook(generally Qsawn) back to straight there is then a weaker slope of grain problem. For fine work it is generally easier to deal with crook than bow by making shorter cuttings and edging the crook out then. Cupping can often be reduced by drying the shell relatively fast and letting that stronger dry shell hold the wood in place while the core finishes drying.

[jbjbuild]

Thanks guys for the explanations.

[nativewolf]

Got nothing but thanks to all for a very educational thread.  This is what makes the forum special.  

[E-Tex]

Thx YH.

[Tramp Bushler]

 Lots of education for me ! 
 Tho we have very little hardwood up here. I am wanting to mill white birch for flooring. But I worry about warpage, cupping , bowing and every other way a board can move. 
 
 Thanks for all the insights. 

[WDH]

I try to keep the rings balanced in a board.  Looking at the end grain, I try to keep the ring orientation the same on both outside edges to the extent possible and try to make sure that the pith is centered in the final cant. 

[moodnacreek]

Certain logs will not cut straight boards. In small dia. hardwood the best you can do is 180 turn each board. Elm or hickory come to mind unless short , straight and fat. The best clue is the off center heart, never good. Dark color in pine, a bad sign.  Sweep in a log is always bad but wiggle [low grade stuff] will cut straight. On a sawmill with dogs and extra headblocks the loading position of the log makes a big difference. 






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