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Author Topic: Log stress and sawing techniques  (Read 3518 times)

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Offline dgdrls

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Log stress and sawing techniques
« on: March 12, 2014, 07:51:32 PM »
 

 

http://www.nzffa.org.nz/specialty-timber-market/information-resources/sawmilling/hardwoods/sawing-eucalypt/

Found this article and thought it would be a good one to share.

It helped me better understand tension/movement and sawing techniques.

Best
DGDrls

Offline Magicman

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Re: Log stress and sawing techniques
« Reply #1 on: March 12, 2014, 07:59:59 PM »
I had a customer that wanted me to make a 12X12 Poplar cant and then split it 4 ways.  I told him that it would not work.  He insisted, and sure enough, it did not work.  I made a banana similar to that picture.   :-\
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Offline JustinW_NZ

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Re: Log stress and sawing techniques
« Reply #2 on: March 12, 2014, 08:10:43 PM »
yeah, small eucalyptus is such a pain for that :(

Cheers
Justin
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Offline thecfarm

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Re: Log stress and sawing techniques
« Reply #3 on: March 12, 2014, 08:23:27 PM »
OMG,if I did not know better,photoshop
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Offline drobertson

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Re: Log stress and sawing techniques
« Reply #4 on: March 12, 2014, 08:57:57 PM »
ain't not photo chopping going on there,  it can get real ugly, real quick , I've had first cut heavy slabs jump off the log and off the mill,
only have a few chain saws I'm not suppose to use, but will at times, one dog Dolly, pretty good dog, just not sure what for yet,  working on getting the gardening back in order, and kinda thinking on maybe a small bbq bizz,  thinking about it,

Offline jamesamd

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Re: Log stress and sawing techniques
« Reply #5 on: March 12, 2014, 08:58:53 PM »
Still a lot of good wood in that log......

















Fire wood ;)

Jim
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Offline mesquite buckeye

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Re: Log stress and sawing techniques
« Reply #6 on: March 12, 2014, 09:08:18 PM »
That looks like pretzel board championship material ;D :snowball: :snowball: :snowball:
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Offline JustinW_NZ

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Re: Log stress and sawing techniques
« Reply #7 on: March 12, 2014, 09:10:45 PM »
Im sure others might have had this, but when there a bit bigger and really bad they can jam up on the head frame if your not careful..
now that makes you reach for the saw and go for 'firewooding'  :D

Cheers
Justin
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Offline Left Coast Chris

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Re: Log stress and sawing techniques
« Reply #8 on: March 12, 2014, 09:35:36 PM »
Looks like repeated 16" cuts perpendicular to the trunk would be the way to go.
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Offline WDH

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Re: Log stress and sawing techniques
« Reply #9 on: March 12, 2014, 11:45:51 PM »
If you sharpened the ends, you could make a gig for some really big frogs  :),
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Offline Wellmud

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Re: Log stress and sawing techniques
« Reply #10 on: March 13, 2014, 09:53:01 PM »
Woodmizer building firewood processors now? ;D
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Offline 5quarter

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Re: Log stress and sawing techniques
« Reply #11 on: March 13, 2014, 10:03:48 PM »
You mean it's not supposed to do that?

 ;)
What is this leisure time of which you speak?
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Offline Chuck White

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Re: Log stress and sawing techniques
« Reply #12 on: March 14, 2014, 07:11:47 AM »
If that was on my mill, it would end up being firewood!
~Chuck~
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Offline pineywoods

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Re: Log stress and sawing techniques
« Reply #13 on: March 14, 2014, 10:52:23 AM »
I've had some bad logs, but nothing that bad...Every new sawyer should keep a copy of that pic taped to the mill  ;D Might help educate some customers too ::)
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Offline MattJ

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Re: Log stress and sawing techniques
« Reply #14 on: March 14, 2014, 11:32:01 AM »
So I have a question for you guys from this picture.  I want to play around with timber framing and up to this point I have sawed 3/4-8/4 material without problem but have never messed with anything thicker.  If I want to saw 6x6 posts is my only option to box the heart?  I was wondering if I can saw multiple 6x6's from the same larger log, i.e. from the quarters.  Per the picture it doesn't look like it.  I also have flexibility in species available.  Could use SYP, red oak, tulip poplar, maple...all easily available.

Thanks

Matt

Offline dboyt

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Re: Log stress and sawing techniques
« Reply #15 on: March 14, 2014, 12:10:47 PM »
That kind of splitting occurs because the juvenile wood (within the first 6 growth rings) is under compression as the tree grows.  when you split the wood as the original poster did, the compression is released, like a spring, which bends the wood.  Boxing the heart keeps that compression balanced inside the beam.  You can get more beams out of a log if you keep the edges and corners at least 6 growth rings (12 is better) from the center of the rings, and might get a beam from the center, as well.  The absolute LAST thing you want to do is to get four beams, each with a corner on the pith-- unless you are building a Hobbit house.
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Offline Ianab

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Re: Log stress and sawing techniques
« Reply #16 on: March 14, 2014, 03:05:49 PM »
If the log is big enough you can probably recover 5 beams, in a star shape. One will be heart centered, and the other 4 will be ~3" away from the pith (Free Of Heart).

Most logs won't misbehave as badly as the eucalyptus in the picture, but they generally will move to some degree if you saw them like that.

Ian
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Offline MattJ

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Re: Log stress and sawing techniques
« Reply #17 on: March 15, 2014, 08:26:36 PM »
Thank you guys for the advice. That helps.

Matt

Offline GeneWengert-WoodDoc

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Re: Log stress and sawing techniques
« Reply #18 on: March 16, 2014, 10:18:41 AM »
It is common to use a two saw headrig (both saws cut at the same time so stresses in the can't stay balanced...such as a Skragg saw or double band) to saw logs with stress...growth stresses.  Growth stresses exist throughout the stem, not just in the core.  We do see some stress is yellow poplar and in some pines with compression wood grown in plantations.  Fortunately, we do not have high stress in most of the trees growing in North America.

 Note the sawing with two saws, or any other sawing technique, does not remove the stress, but rather keeps the stress balanced.  Subsequent processing including drying will have warp that makes the lumber or cant unusable.  The literature is full of attempts to make high growth stress timber like eucalyptus perform well, including steaming prior to sawing.  There is no magic bullet.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more


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