Strongest 6x6's

[azmtnman]

Greenhorn question:
  I would have thought that to mill the highest quality, strongest, least-likely to warp 6x6 that I would center the heart in the 6x6. An experienced friend said I should cut the heart out.
  I realize my friend is probably right but he is also not a sawyer, but a well-versed, highly educated wood products salesman.
  What say ye?
 

[beenthere]

More to it than "just cut the heart out" I believe.
With due respect, have to wonder what your "friend" is basing his suggestion on... there are several variables that will affect the quality, the strength, and the potential to warp.
Also add to that the minimum quality, strength, and warp that is acceptable for the application of the 6x6.

The ultimate within a species, would be clear, straight grain wood. Then other factors can affect the strength of that clear, straight grain wood such as growth rate. Between species, there are other variables that will affect the strength.

And is your friend suggesting that the "heart" is the pith or thinking that the heartwood is weaker than the sapwood. There would be a difference.

I don't mean to cast any doubts on your highly educated wood products salesman, but do wonder just what he/she means by "cut the heart out" for the highest quality, strongest, least-likely to warp 6x6.

Add to this, that the size of the tree/log that the 6x6 is taken from, also plays a role in whether centering the pith is advisable or not. i.e. some giant redwood or other large tree would yield 6x6 timbers without pith and meet your friends suggestion. But then these large trees are often mostly heart.

But leaves the question if azmtnman has such material to saw. Let us know what you have available.

Just raising some questions, in response to "what say ye?".    ;D

[longtime lurker]

kinda sorta maybe...

Pith timber is weak. How weak depends on species. How much of it there is depends on species also, but into that you need to factor the individual tree because due to growing conditions and location the amount of pith in a given tree can vary from place to place and tree to tree.
But pith timber is weaker, theres no doubt about it.

Under the grading rules here, we can put pith into structural grade softwoods. I dunno exactly how much because I don't cut softwoods.
But we can't put pith into structural grade hardwoods - and I'm in Australia where hardwood means hard-like-you-wouldn't-believe-wood - at more then 1/9th of the cross sectional area of the timber. Under the definition of heart under those same grading rules that works out at 7" x 7" as a rule of thumb, though there are about three of the eucalypts where you might just sneak in a 6 x 6... maybe... on a good day... if you're feeling sorta adventurous. So 7 x 7 it is.
A 6x6 structural grade hardwood here has to be heart free.

Your grading rules there are different, and I'm not that familiar with them. But I'd say that your friend is possibly right, and definately right about the strength issues.

[bkaimwood]

You guys got it all for azmtnman...pretty much anything that contains the pith will be weaker...the degree of the weakness will vary first and most importantly based upon species, but as mentioned also varies widely by tree and log size...for example, cut a 6x6 from a large oak log...in many cases, it will be the ugliest, worst 6x6 you ever see...if the pith isn't already cracked, it will be...on the other hand, I've cut plenty of them from high quality white pine logs with no issues and made many nice 6 bys and 7 bys...all in all, stay out of the pith, stay out of the sapwood, and you'll make 6 bys that reflect the log quality... As far as strength? For a simple fella like me I use all the typical/common old school timber related books...did u know a high quality 6x6 of just pine will support nearly 10k lbs!!??...and that's just one...wood is a beautiful thing!!

[beenthere]

bk
If you are going without the pith centered, then you best account for the warp.
There are reasons, and good ones, for boxing the pith. Stress relief and differential shrinkage are a couple of them.

[azmtnman]

I forgot to mention, I'm milling ponderosa pine.

[bkaimwood]

No doubt beenthere, I think we missed each other a bit, or my words left the wrong idea...and/or I am not totally getting what your saying...my wife says I'm slow, and I'm new, so learn me...I'm with ya on centering on the pith for best dimensional lumber quality...my friend Magicman (whether he knows he's my friend or not), previously helped and learned me in another thread, after I had issues with pith cracks, and referred my to an earlier thread tutorial he did about dealing with pith cracks in cherry logs he had...so what I said was relating to pith cracks, which are more notorious in certain species, but a risk in prolly everything, and that some things won't make good dimensional lumber from a center can't, but other stuff can still be OK, or better, strength wise...so centered, yes, but the center being good, maybe not...also with ya on the outer stuff being more likely to do the undesirable stuff...more so if its not centered...

[beenthere]

Warp probably causes more frustration (and rejection) when making timbers than knots and pith-related cracks.
Strength-wise, if the timber (i.e. keep talking 6x6 here) is used as a post, then pith center will not affect it's task used in compression. However there are limits to load due to being a column.

If it is used as a beam, then the limiting strength comes in the tension side (top where load is at) and is affected by knots and associated steep grain around knots. The small pith cracks only will affect the shear properties and not as important or significant as the tension properties.

Wood is very strong in tension along the grain, but pretty poor in tension across the grain, so any deviation of that grain from parallel to the tension forces reduces the strength.  Structural grading pays particular attention to the deviation in grain from being parallel (or perpendicular to the load).

My point is that centered pith will give one best results for acceptable warp, and will not reduce strength significantly over timbers that are not centered around the pith.  But as we covered with Jim Rogers, there is no structural grade requirement of pith to be centered.

[Grandedog]

Howdy,
If you box the heart it will be stronger than having the heart off center. Getting the heart within 2" of the face will cause issues. It will warp less but will be susceptible to checking. FOHC would be the strongest and least likely warp. Are you doing posts, or beams?
Regards
Gregg

[bkaimwood]

Thanks for clarifying beenthere... I've only gotten far enough in my reading and edumication so fibrous strength is god to me...with some smaller things thrown in...I need to watch some more videos, do some more research, and get more mill time to get a grip on the tension part...but I look forward to it, with the help of schooled veterans like u guys!!!

[golddredger]

I cut a bunch of Ponderosa. About 99% of what I cut is Ponda. I have tried numerous cuts and found the beams that hold the straightest for me are those cut with the heart boxed and dead center as much as I can. If I am sawing square posts I just center the pith and cut. If I am making beams to span a good distance I add to the sides and get as much wood as I can for whatever I am building to add as much strength top to bottom as will fit my plans. I did some very very large beams like this last summer for my sawmill shed. They are 8"X21" X 22ft LONG and they are cut with the pith centered. I have not gotten more than 1" of deflection in the entire beam after all winter and this summer so far. Not bad at all and by far the best beams I have made. I cut the last set but to the side of the pith and that beam tweaked a full 8" of bow in the middle from end to end. Never again will I waste my time cutting the pith off center for beams and post. Yes you will get some check down the side but these bads boys are solid as a rock now that they are dry.

[WDH]

From your pic, it is easy to make out the juvenile core.  Keeping it in the center with mature wood all around it makes it behave better.  If you put the juvenile core on the edge of a board, beam, or post, it will warp in a "C" shape.  That is because the juvenile wood will shrink a little along the grain, but the mature wood on the other side will not, and this stress pulls the piece into a "C" shape.

I went to Lowes today to buy a couple of treated posts.  They almost all had the pith on the edge of the post.  Poor sawing. 

[POSTON WIDEHEAD]

I went to Lowes today to buy a couple of treated posts. 

I'm scared to ask what Lowe's is getting for treated wood now. 

[WDH]

The 4x4x10 posts were about $1.30/BF, but that is a real BF calculated as a 3.5x3.5x10, not a fake BF calculated at 4x4x10  . 

[sandsawmill14]

we always center pith on post but have never sawn beams like that. we always build beams by sawing 2x12 or 2x16 or whatever we need and put them together crown up then down then up then down to make 8" beams but same pattern regardless of whether it was 4" or 10" beam.  i dont know if thats the best but i know they will NOT sag .  i can remember using them up to 24' long  but we built some 40 footer back years ago but we put 1/2" plate steel between the 2 layers of wood they were either 12" or 14" i cant remember. only solid beams we ever used were for a bridge but we only trimmed 1 side enough to get a good surface to nail top on. they were about 20" dia on small end  made a good bridge though

[azmtnman]

Thanks for all the input and educating the ignorant! 
I am cutting beams. Right now, my material will be used to build BIG swing sets/playground equipment. I think they will be constructed with overkill.
  I also should have added that 99% of what I'm milling is beetle killed ponderosa and is probably as dry as it will get.

[Ianab]

Heart centred is generally the most stable. The juvenile wood may not be the strongest, but if you cut out the posts like Golddreger's pics, you get good beams because any tension in the wood is balanced, and they should stay straight.

But if the log is big enough you can argualbly cut stronger beams completely free of the pith. A larger log might yeild Five 6x6s in a cross shape. One will have the pith centred, and the other 4 will be completely free of it. They will be cut ~3" away from the pith, technically stronger, and should still be stable.

What you want to avoid is cutting just 4 beams from a log in a box shape. That leaves you with the pith on the corner of each peice. That's asking for problems and the pieces will move as the juvenile wood around the pith actually shrinks in length as it dries.

So it's either pith centred, or keep right away from it.  Don't leave the pith on the edge or corner.