pith

[Mike_Barcaskey]

I know to saw around it and discard, but dont know why I'm doing it.

what's the matter with the pith?

alot of times I keep it centered in 6x6 and 8x8's to be used as bearers or posts or what not

[Cedarman]

In some trees pith is a small hollow core. It is usually the first place that will crack in a board.  Even ERC that does not have pith will tend to crack along the first growth rings.

[mike_van]

Mike - sawing beam sized stuff, you need to keep the heart centered as much as possible -  I've tried to make 4x4's by splitting an 8x8, usually you get skis or banana looking ones.    Most major checks will go to the pith, if you get rid of it [as opposed to leaving it in a 2x12 etc.,  I think you are better off.

[pigman]

Mike, when I build furniture with boards that have pith in them the customers get pithed off. They don't like big cracks, splits and warped boards in their furniture. :(

[beenthere]

Mike, the pith center is a guide to keep balance in the stresses that vary as you go away from the pith. To keep your 6x6's etc from bending too far out of 'straight', those stresses need to be balanced and centering around the pith is how, in most woods, you do that.

The pith is likely the lowest quality wood, in terms of strength, and in terms of having the likely-hood of most grade-reducing defect such as knots, cracks, abnormal wood, and what is called 'juvenile' wood (very low strength for a number of reasons), along with what was said already. And it depends a bit on the species you are sawing.

[mike_van]

pigman [bob] -  :D :D

[solodan]

Sometimes I don't even worry about it. I guess it depends on what I am cutting. I cut alot of Sugar Pine and Ponderosa, and i've cut 1x with the pith through one face with no problem, other times i've seen it cup. lots of pin knots near the pith in ponderosa, but so much of the ponderosa here gets milled  for v-rustic panel. the boards that get left behind in the lumber yard seem to be the ones with no defects.

[Mike_Barcaskey]

pigman  :D

thanks for all the replies, any other thoughts?
such as, a rule of thumb... if the log is 18" dia how much of the pith do you saw out?
is it a constant ratio?
I usually saw the boards I want around it and "pith" what's left over in the center, sometimes its 2x2, 1x4 or 3x3 or whatever. If its larger than 4x4 I make a board out of it

mike van, when you split your 8x8 into 4x4's the pith now runs along one corner of the board, causing it to warp/twist. correct? I've never cut a board like that

[rbarshaw]

pigman  :D



mike van, when you split your 8x8 into 4x4's the pith now runs along one corner of the board, causing it to warp/twist. correct? I've never cut a board like that

I've cut an 8x8 16' green sweet gum, had the pith centered, was perfectly straight, into 4x4's, they were bowed so badly that the center of the post was 3' off from the ends .

[Ianab]

a rule of thumb... if the log is 18" dia how much of the pith do you saw out?
is it a constant ratio?

Depends on the species mostly...
Stuff like pine you can saw right through the pith, you get a couple of low grade boards, with pith and knots etc, but they wont split.
With the local cypress I usually have to loose a 2x2 to avoid splitting as the boards dry.
Eucalyptus I've sawn developed 6" splits around the pith as I was sawing it 

So.. ummm.. it varies.

Cheers

Ian

[mike_van]

Mike, thats correct, the pith would be on 4 corners -  I needed a lot of 4x8's for my barn, so I made 8x8's and halved them,  [all oak]  some peeled up, some stayed straight. Usually only hardwoods do this -  In large oak, i've gotten down to an 8x8 and had it all spider-webed,  not a sound face left - thats a lot of pith!  You won't get a sound board-beam out of this -  short cribbing blocks, maybe - or firewood.   

[Cedarman]

You folks and all your pithy wood.  Since I don't keep my stickers straight, leave wood in the rain for months at a time and slice straight through when sawing a log, I need a wood that would lay flat, not have a pith, not rot in the rain and not bow when the stickers don't line up.  Now you know why I saw eastern red cedar.

[tnlogger]

 when I was sawing ties I did a lot of gum I learned the best thing to do was saw big I say big slabs and no side lumber  :D :D :D

[Tom]

The pith is the trail that the growth bud of the tree left behind as the tree grew.   It is the center of the juvenile wood which extends 3 to 6 growth rings beyond it.  (rule of thumb)

Since wood doesn't move "up" as the tree grows it is layed down a layer per year (rule of thumb)  to produce a lengthening trunk that is built with much the same geometry as a candle. 

Beenthere's description is pretty accurate in my opinion.   centering the pith helps to center the stresses.  unfortunately the pith doesn't always form a straight line as the bud of the tree lays on another layer.

The Pith is generally considered the weakest part of the tree and is followed by the next few "rings" until the tree begins to lay down Mature wood. 

A google search should reveal many articles on Mature and juvenile wood.