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Is it a Drying or Sawing Dilemma

Started by Glenn1, May 19, 2016, 09:56:24 AM

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Glenn1

In the past, I have had some problems with the kiln dried boards cupping.  I contacted "Yellowhammer" and we discussed my issues.  It seems that the sawyer had been only cutting the boards from 2 sides of the logs to get the widest boards.  It worked fine on the outside boards but as he cut closer to the pith, the rings had more curve which increased the cupping.  YH sent me a drawing showing how he cuts a log.  It has significantly made a difference in cupping.  Recently, I took a load of beautiful hard maple from the kiln.  It was very white and also very flat.  The new method of cutting made all the difference in the world.  I hope that YH will chime in.
Vacutherm IDry, Nyle 53 Kiln, New Holland Skid Steer, Kaufman Gooseneck Trailer, Whitney 32A Planer

WDH

Post the drawing if you can.  Or maybe YH can. 
Woodmizer LT40HDD35, John Deere 2155, Kubota M5-111, Kubota L2501, Nyle L53 Dehumidification Kiln, and a passion for all things with leafs, twigs, and bark.  hamsleyhardwood.com

Glenn1

 

 


Here is the diagram that YH sent me.  It really makes sense and eliminates one cause of degrade.
Vacutherm IDry, Nyle 53 Kiln, New Holland Skid Steer, Kaufman Gooseneck Trailer, Whitney 32A Planer

4x4American

Man, he is so good he can make two cuts at once (cut 4). lol

How do you make cut 7? 

Thanks for sharing.

You put yellohammer in quotes like this "yellowhammer" and it got me to thinking, how did you come up with that name, Robert?  Was it a stanley hammer? 
Boy, back in my day..

YellowHammer

I was very glad to help Glenn1 out.  He was having trouble with some of his sawyers boards cupping badly and he sent me some pictures.  From that, I was able to see that their sawing pattern was off and causing excessive cup.  So I whipped up this diagram to illustrate the sawing pattern I use most of the time because its fast and really produces flat boards.

This pattern minimizes and balances the sapwood on the wood, no matter how thick the sapwood is, and gets relatively constant grain angles on all the boards.  The sapwood will always pull the boards and cause bow, which is about the only defect that can't be removed except by a jointer, but then thickness suffers.  So this pattern is extremely useful for sawing boards that come off the mill with very little heartwood/sapwood mix.  Even logs like maple, poplar, and oak work well with this pattern, but it truly does great with cherry.  For example, most mills around here through saw poplar, and the boards cup as they are a heavy mix of heartwood and sapwood.  However, this pattern will result in almost full sapwood boards, or almost full heartwood boards, so there is almost no cup or bow when drying. 

I like to get the best boards forming down to the rectangular cant, then make it to a to standard size, I like 6 1/8" or 8 5/8" x whatever and start taking constant width boards from there.  Then stop near the pith and take those boards as they get smaller.  Also, it important to resist the temptation to get the ultra wide through sawn boards as they will cup.  With a hydraulic mill, this kind if sawing pattern goes very fast, and its easy to accomplish the rotations and get all standard width boards. 

Its also important to look for a big pith or stress crack.  Most people saw parallel to those, but as they are usually caused by stress, the boards will bow.  I like to saw perpendicular to the stress cracks and the boards will curve but will be flat.  I can edge curve.  The length of the stress crack dictates how wide I make my cant.  Most of the time, even though the log has stress, the boards will come off the mill dead flat and will not cup or bow when drying.

The Yellowhammer is the State bird of Alabama, as well as in the Crimson Tide fight song.  Roll Tide.  The yellowhammer bird itself has always been lucky for me, and "hammer" also sometimes describes my approach to getting things done, or so I have been told. 
   
YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

4x4American

OoOOooOh!  I never woulda thunk'd it!

I'm gonna try that sawing method for sure.  Do you like to position the sweep in the log so you get crook instead of bow? 

Boy, back in my day..

Ianab

Strangely enough, that sawing pattern is pretty much what you would end up with on a Swing Blade mill. Just the cuts would be in a different order, and the wider boards might end up in 2 pieces.

On a swing blade you would start at the top, taking off the waste, then some horizontal boards, edges as you saw them. Then switch to vertical boards once you are maybe 1/3 of the way down. Take the vertical boards each side of the pith, and do whatever seems best with the wood around the middle. Some species you can use that, others it's horribly cracked and only good for firewood. Then back to horizontal for the last cuts.

You can have issues with tension in the log, but you keep the L shapes waste in place as you are cutting, and that seems to help stabilise the log.

But the thing is you end up with a similar ring orientation in the boards
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

jim blodgett

Interesting to me that this method of sawing doesn't yield any vertical grain boards, which are the most dimensionally stable over time - at least in soft woods.

GeneWengert-WoodDoc

Cupping is more likely as pieces get closer to the pith, as the shrinkage difference between the bark side and the heart side is the greatest.  The YH pattern minimizes this indeed.  Also, did you know that a wide board that is cupped will have 1/4 as much cup if the piece is ripped down the middle?  In the old days, we had a saw in the mill, called a busting saw, that did just that.

Drying also affects cup potentially in three ways.  Slow drying means more cup.  Rewetting when partly dried means more cup.  Over drying, under 7% MC also means more cup.

Quarter and rift sawn lumber seldom has much shrinkage difference, one face compared to the other, so this lumber seldom will cup at all.  Flatsawn has the most.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

GeneWengert-WoodDoc

Most prone to cupping is this sawing pattern



Somewhat less prone to cupping is this pattern


A little bit better is this pattern


Even better is this pattern with quarter and rift



And the best is
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Ianab

Quote from: jim blodgett on May 20, 2016, 10:39:15 AM
Interesting to me that this method of sawing doesn't yield any vertical grain boards, which are the most dimensionally stable over time - at least in soft woods.

This is true, but quarter sawing (vertical grain) is a lot more work on a band mill because you have to unload quarters of the log and process each section individually. Sure you can do it, but it's slower.

Also, some logs and species are best flat sawn. The grain of walnut looks much better, and if you Q-saw a knotty log you end up with a lot of "spike" knots running across many of the boards. Where flat sawing would put the knots in the face of the boards, and they are still usable,
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

bkaimwood

YH's simplified pic is great, and basically how I saw...there are a few more pics that were good also... softwoods are more forgiving, but with hardwoods, its the way to go...it shows getting your wide boards from the top and bottom, but stopping way short of the pith...then flipping to get your narrower boards from the sides...stable, yup...not the widest boards possible..yup...but indeed, the highest quality boards without getting into quartersawing...and the reason is, centered pith, and more importantly, far enough AWAY from the pith...the pith will nearly always degrade lumber...
bk

WDH

Quote from: bkaimwood on May 20, 2016, 08:11:47 PM
the pith will nearly always degrade lumber...

In cherry, it will ALWAYS degrade lumber  :)
Woodmizer LT40HDD35, John Deere 2155, Kubota M5-111, Kubota L2501, Nyle L53 Dehumidification Kiln, and a passion for all things with leafs, twigs, and bark.  hamsleyhardwood.com

YellowHammer

As the title of the topic indicates, since Glenn1 was seeing the results of the lumber degrade at the end of the drying cycle, we naturally assumed that it was a problem with the kiln or his drying technique.  He really showed his perseverance by checking and double checked everything.  Also, since he was using experienced sawyers, it was also assumed they knew what they were doing, but in the end, the sawyers were just slicing cheese.  So when he convinced the sawyers to adjust their technique, and since he had his kiln dialed in, the results were immediate with it cranking out top quality kiln dried boards. 8) 

One thing I like about this pattern is that with Accuset and programmed drops of 1 1/8" to allow for the 4/4 hardwood scale, it will result in a center cut 4x4 at 3 5/8" x 3 5/8".  So instead of having useless 1 inch thick pith boards, I end up with "farm grade" utility 4x4's which I stack on a pallet and sell green for $10 each.  Sometimes cherry has such poor pith they cant be saved, but oak especially generally results is nice, sellable 4x4's. 
YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

WDH

Yeah, sell them green before they crack  :D. 
Woodmizer LT40HDD35, John Deere 2155, Kubota M5-111, Kubota L2501, Nyle L53 Dehumidification Kiln, and a passion for all things with leafs, twigs, and bark.  hamsleyhardwood.com

YellowHammer

YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

WV Sawmiller

   Great info. Only concern I have was YH comment about sawing perpendicular to the check/crack. Everything I had ever read was to cut parallel to the crack so you did not end up with a split in every board.

   How do you prevent the split boards?
Howard Green
WM LT35HDG25(2015) , 2011 4WD F150 Ford Lariat PU, Kawasaki 650 ATV, Stihl 440 Chainsaw, homemade logging arch (w/custom built rear log dolly), JD 750 w/4' wide Bushhog brand FEL

Dad always said "You can shear a sheep a bunch of times but you can only skin him once

YellowHammer

Quote from: WV Sawmiller on May 21, 2016, 07:53:58 AM
   How do you prevent the split boards?
This is where it gets a little tricky.  Once a crack gets to the point that it extends out of the pith, it generally means that it is caused by stress in the log, and is in fact, strong enough to make the entire half sections of the log curve away from its central axis and bow outward.  The boards will do the same.  Reading the stress crack tells me what I have have to do to get a flat board. 

Another thing to consider is my sellable end product, which must be flat, straight boards.  As I said earlier, just about the only defect that I can't do anything about is a bowed board.  If I have a board with a major bow, so much that I can't cut it in half and joint it, then it's a dead board to me, and more importantly, my customers, even if it has no cracks.  It's too easy for them to put it back on the rack and pick out a straight one.  So it will never sell.  If it is an 8 foot board, with a foot of end crack, but flat as a pancake, then I can cut it back to 7 foot and sell that, or instead, simply rip the crack out and sell it as two 8 foot but narrower boards. 
So, as I am squaring the cant, I'm always putting my opening cuts either parallel or perpendicular to the crack, and watching closly at how the slabs and first flitches behave as they come off the mill.  Typically, and we've all seen it, a board that is parallel to a major stress crack will bow up off the cant like a carrot peel, becuase it contains some of the fibers that are causing the stress crack in the first place.  It sometimes gets tricky trying to decide how much the sapwood is contributing to this, but after awhile, not a big problem.

If the boards are sawn perpindicular to the major stress cracks, then the stress in their fibers will cause them to crook or curve sideways, but remain flat.  Most folks have seen this also, when they are sawing a cant and instead of the board lifting up, it's leading edge will visibly spring sideways, but the saw kerf will not open up.  This board will remain flat all the way through the drying cycle, although it will have to be straight line edged. 

Also, the stress cracks generally, hopefully, don't extend all the way across the face of the log, but usually stop somewhere in the meat of the heartwood.  So I will form the cant sawing perpindicular to the heart check, in the non-cracked wood until I just hit the end of the split.  Then I rotate 180 and get all the boards from the other side until I just hit the tip of the check.  All these boards will be perfectly flat and have no cracks in the ends.  So now I have a cant that is the width of the stress crack, and I have a decision to make.  Either saw perpindicular to the crack, and get flat boards with splits or saw parallel and get bowed boards with no splits.  Usually, I'll take a parallel to crack test cut and see what happens.  If I get a carrot peel, then I have no choice but to go back to sawing perpindicular, get the boards with end cracks and deal with it later.  If I get a flat board with no opening of the saw kerf, then it means I removed the parts from the log that were causing the stress and I can continue to saw parallel to the crack and again get flat boards with no cracks.
Anyway, long answer, but I hope it makes sense.   
YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

xlogger

Thanks Robert, I'm watching this post close. I too had cup problems to start with and less now cutting 8/4 slabs. I'm trying to save some thickness on the pit cut sections and just cut the pit out and saw 4/4 out of it or like you suggest to have 4x4 pit cut to do whatever with. I change up my sawing methods on cutting the 4/4's out of a whole log like you suggested also. I had to quit trying to get all the wide boards I could. You are right the customer just puts them back down if they are cup or a 4/4 board is bowed.
I've been cutting cedar so long I didn't have much problems with them just plain flat sawing them.
Timberking 2000, Turbo slabber Mill, 584 Case, Bobcat 773, solar kiln, Nyle L-53 DH kiln

Ianab

Better to have 2 x good 6" wide boards than a cupped or split 14" board....

Hence ripping out the unstable wood around the pith can leave you with 2 good boards, rather than one bad one.
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

WDH

On species that split at the pith like oak, cherry, sycamore, etc, better to get the pith wood and the part that will crack out by edging while sawing at the mill, or you will have to handle the board again a couple of more times down the road  :)
Woodmizer LT40HDD35, John Deere 2155, Kubota M5-111, Kubota L2501, Nyle L53 Dehumidification Kiln, and a passion for all things with leafs, twigs, and bark.  hamsleyhardwood.com

longtime lurker

Theres a little book, long out of print, with one of the most detailed diagrams of quartersawn breakdown patterns as used in an Australian hardwood mill I've ever seen.

It was written for equipment that was common at that time here - Circular "canadian twin" breakdown saws with a throat capacity up to 60" for regular logs, or the big single sashes they had up here that could handle 9 footers (and I can remember seeing them dynamiting the oversize when I was a kid, its a LOT of log when it wont pass through a 9' sash frame)- and breast benches for secondary and tertiary cutting.  Sashes are all gone now, and breast benches are getting pretty rare... manpower inefficient and dangerous things they are, but there are times when there is nothing better then a 4 man bench so theres a few holdouts.

Anyway, thanks to the wonders of the internet the book is available as PDF. We mighnt use a breast bench anymore, but "modified to my gear" versions of these cut patterns are what I still use today. Well, except for the small log patterns, but back when it was written no-one woulda thunk to bother with a log under 2' across.

Chapter 3 has the sawing patterns. The rest might be of some interest from a historical perspective, but thats about it.


The quickest way to make a million dollars with a sawmill is to start with two million.

JustinW_NZ

Thanks for posting that Longtime Lurker, very good 'old read  :P

Ian - I often keep two quarters on the bed of the band mill and process both at once if its not super large or tough stuff that requires critical care.
Makes it very fast!
And there's no way I would even drop the hydraulics off my mill because most of what we do is quarter sawing.

Cheers
Justin
Gear I run;
Woodmizer LT40 Super, Treefarmer C4D, 10ton wheel loader.

customsawyer

When it comes to the stress cracks in the end of the logs and I was sawing for grade I found it best to keep the crack at a 45°. This would let me edge the crack out of the boards. Keep in mind that I was not drying or trying to sell the lumber.
Two LT70s, Nyle L200 kiln, 4 head Pinheiro planer, 30" double surface Cantek planer, Lucas dedicated slabber, Slabmizer, and enough rolling stock and chainsaws to keep it all running.
www.thecustomsawyer.com

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