Log stress and sawing techniques

[dgdrls]

 

 

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

[Magicman]

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.   :-\

[JustinW_NZ]

yeah, small eucalyptus is such a pain for that :(

Cheers
Justin

[thecfarm]

OMG,if I did not know better,photoshop

[drobertson]

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,

[jamesamd]

Still a lot of good wood in that log......

















Fire wood ;)

Jim

[mesquite buckeye]

That looks like pretzel board championship material ;D

[JustinW_NZ]

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

[Left Coast Chris]

Looks like repeated 16" cuts perpendicular to the trunk would be the way to go.

[WDH]

If you sharpened the ends, you could make a gig for some really big frogs  ,

[Wellmud]

Woodmizer building firewood processors now? ;D

[5quarter]

You mean it's not supposed to do that?

;)

[Chuck White]

If that was on my mill, it would end up being firewood!

[pineywoods]

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 :

[MattJ]

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

[dboyt]

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.

[Ianab]

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

[MattJ]

Thank you guys for the advice. That helps.

Matt

[GeneWengert-WoodDoc]

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.