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Questions about the pith

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Forum topic by Steve posted 10-24-2018 02:05 PM 889 views 0 times favorited 13 replies Add to Favorites Watch
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Steve

1344 posts in 999 days


10-24-2018 02:05 PM

Topic tags/keywords: pith

I’ve read about the pith and how you should avoid it. But what about all those large slabs? Do none of them have the pith in them? Can the pith still be included in boards used?

I recently had a bunch of cherry chunks sliced up and a few panels are almost ready to start building with. Do I need to cut around the pith on those as well? Or could i possibly use the entire piece as one large panel?

I’ve read mostly about the pith while turning bowls, but I’m still curious about all those large slabs people work with.


13 replies so far

View msinc's profile

msinc

567 posts in 920 days


#1 posted 10-24-2018 02:25 PM

This is an excellent question….one I have also wondered about, but never got any real, tangible answers. You see, there are just some things that we cant talk about. Once some one has gotten on here and blasted off about that terrible pith and how bad it is and what all must be done about it then they simply cannot answer the question like the one you have posed. To do so would require “backing up” and explaining themselves and those kinds of people would rather move on to the next issue to preach about than get the first one right. If that pith is so terrible then why is no one cutting it out of live edge slabs? I have never seen any one remove or otherwise work around or address it.
I am sure they will come up with some kind of half baked excuse like “it’s mainly only in certain types of wood”, etc. “oh, I thought you were talking about X42-3 wood…..you mean cherry? Well, that’s different….”

Edit: in answer to the main question, I saw and dry all my own wood. Wild black cherry is a very popular one around here so I use a lot of it. If I have a slab that is dry and is not split I use it as is and I have yet to see any problems with any of it. Now, if it’s split down the middle, and I am not saying this cannot or does not happen, then yeah, you will have to work around it. But to arbitrarily just gut the center of every board in fear of what the future actions of the dread pith might be…...no, I do not.

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GR8HUNTER

6204 posts in 1129 days


#2 posted 10-24-2018 02:34 PM

maybe mythbusters should do a show on this subject LOL :<))

-- Tony---- Reinholds,Pa.------ REMEMBER TO ALWAYS HAVE FUN

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Fresch

434 posts in 2337 days


#3 posted 10-24-2018 02:46 PM



This is an excellent question….one I have also wondered about, but never got any real, tangible answers. You see, there are just some things that we cant talk about. Once some one has gotten on here and blasted off about that terrible pith and how bad it is and what all must be done about it then they simply cannot answer the question like the one you have posed. To do so would require “backing up” and explaining themselves and those kinds of people would rather move on to the next issue to preach about than get the first one right. If that pith is so terrible then why is no one cutting it out of live edge slabs? I have never seen any one remove or otherwise work around or address it.
I am sure they will come up with some kind of half baked excuse like “it s mainly only in certain types of wood”, etc. “oh, I thought you were talking about X42-3 wood…..you mean cherry? Well, that s different….”

Edit: in answer to the main question, I saw and dry all my own wood. Wild black cherry is a very popular one around here so I use a lot of it. If I have a slab that is dry and is not split I use it as is and I have yet to see any problems with any of it. Now, if it s split down the middle, and I am not saying this cannot or does not happen, then yeah, you will have to work around it. But to arbitrarily just gut the center of every board in fear of what the future actions of the dread pith might be…...no, I do not.

- msinc

If it splits during drying cut it out if not it stabilized.

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HokieKen

9911 posts in 1555 days


#4 posted 10-24-2018 03:12 PM

Let’s remember there is not pith in every board. Only the one sawn from the center of the tree. For me, I cut my turning blanks or slabs from the tops and bottoms of the log then cut narrower pieces on each side of the pith. I have had the pith cause me problems in the past with turning stock but haven’t used any lumber with pith in it. I see no reason to tempt fate. It makes sense that the highest concentration of stress will be at the pith because that’s where growth rings are the smallest and consequently it has the least ability to expand/contract without separation and cracking.

That being said, if I needed a live edge slab and the center of a log was the only place wide enough to get it, I’d leave the pith in and see how it behaved while drying. Then make a decision on whether or not it was appropriate for my project.

-- Kenny, SW VA, Go Hokies!!!

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lumbering_on

578 posts in 906 days


#5 posted 10-24-2018 03:17 PM

Pith in a small round bowl may be a concern, but in a huge slab?

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Woodknack

12842 posts in 2796 days


#6 posted 10-24-2018 03:46 PM

Lumber suppliers manage to dry 2×4 and 4×4 with pith so it can be done. For most of us, if we dry wood with pith, it will check because wood is drying at different rates. My hardwood dealer doesnt sell wood with pith and I choose to remove it, but the freedom of being a woodworker is you get to do it your way.

-- Rick M, http://thewoodknack.blogspot.com/

View Tony_S's profile

Tony_S

976 posts in 3499 days


#7 posted 10-25-2018 10:27 AM



This is an excellent question….one I have also wondered about, but never got any real, tangible answers.
- msinc

What I was taught, and have learned….
The pith, and the first 2 or 3 inches around the pith are from when the tree was young and growing very quickly. Because of the more rapid growth, there’s much more space between the rings(summer and winter growth). The rings, and mainly the winter growth rings, because they’re much more dense, are a good part of what determines the stability of the piece of wood. Thats why old growth lumber is considered to be much more stable, because of the number of rings per inch. Old growth Douglas Fir and Western Red Cedar are good(extreme) examples of this. The reason they are so stable, is because they can have outer diameter ring counts of 50-60/inch. Move to the center of the tree and you may get 3-4 rings/inch.
With that said, if that center portion is captured in the middle of a 30” slab, as long as the pith is dry and stable(relatively speaking) is should remain that way because the outer diameter of the tree is holding position. If the outer diameter dries ‘wonky’, the first place the slab will usually split is the center, because it’s weaker/less stable.
Now if you take the outer sections away, and you’re left with a 2×4 for example, once it dries, you’ll end up with a 2×4 propeller or a 2×4 that looks like a dogs hind leg depending on the tree and how straight the pith section is relative to the 2×4.

Is all this a hard and fast rule? No. Wood is never hard and fast.

-- It is the mark of an educated mind to be able to entertain a thought without accepting it. Aristotle

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bondogaposis

5452 posts in 2767 days


#8 posted 10-25-2018 01:51 PM

Pith can cause a lot of problems. Most of the problems stem from the juvenile wood that surrounds the pith. Juvenile wood can actually shrink in length whereas for the rest of the tree it cannot. If a board is cut in such a way that the pith and surrounding juvenile wood is on one side of the board it can cause the board to bow, sometimes severely. However if the pith is in the dead center of a board it is balanced and may not cause problems except for checking. Go to the home center and look at a bunch of 2×12s a lot of them will have the pith in the center. Some with the pith off center will be bowed to pith side.

-- Bondo Gaposis

View Snipes's profile

Snipes

409 posts in 2661 days


#9 posted 10-25-2018 03:48 PM

I think certain species are more problematic? Pine for instance they always leave in, generally it’s boxed as Bondo noted. Oak species I think they try to remove it. Hopefully Danny (WDH) will chime in he’s the expert on wood and sawing.

-- if it is to be it is up to me

View AZWoody's profile

AZWoody

1452 posts in 1640 days


#10 posted 10-25-2018 07:20 PM

I don’t know why it would be something to not talk about. Some woods crack more in the pith than others.

Slabs that have pith in them tend to have more cracks in the middle than those that don’t, and the species determines how much. It’s not a half baked excuse, it just is how it is. If it’s eucalyptus, like I mill, the pith will split and cause all kinds of cracking. I had a log I picked up that had been sitting a few months that was 4’ x 15’ and the middle was all messed up from end to end.
I ended up quartersawing it and eliminating much of the center of the log.

If I’m milling Mesquite, the center is rather stable and doesn’t cause a problem.

If you’re saying slabs don’t crack, check the end grain to see if you’re seeing a slab from the middle. Only 1 or 2 slabs from a whole log will be from the middle while the rest of them come from above and below.

Also, many people will cut out the bad portion and epoxy fill and use the cracks as a feature or use each half separately. Remember, the pith is not in all the slabs from a log.

Another reason the pith is talked about is because of turners. They usually deal with green wood for rough turning so the pith will usually cause problems as it will dry at a different rate as the rest of the blank and can ruin a piece pretty easy. So, when cutting blanks, it’s highly recommended to cut out the pith when making blanks. It ups the chances of a successful turning.

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WDHLT15

1816 posts in 2892 days


#11 posted 10-26-2018 12:56 PM

The comment about juvenile wood is spot on. The juvenile core behaves differently from the mature wood around it. The small bit of longitudinal shrinkage that occurs in the juvenile core causes problems, more so in some species than others. Generally, softwoods like pine, spruce, and fir do not split at the pith. It is standard practice to include the pith in construction lumber.

The pith can behave badly in some hardwoods. The oaks, cherry, and sycamore tends to always split at the pith. I usually include the pith in these hardwoods, let them split and do their thing while drying, then cut out the split area once the boards are dry. This gives two narrower boards on each side, but at least they are quartersawn. With thick slabs, you can cut the split out and re-glue, or either fill the cracks with epoxy or glue and sawdust. It depends on the look that you want.

-- Danny Located in Perry, GA. Forester. Wood-Mizer LT40HD35 Sawmill. Nyle L53 Dehumidification Kiln. hamsleyhardwood.com

View Steve's profile

Steve

1344 posts in 999 days


#12 posted 10-26-2018 01:07 PM

Very informative posts so far, so thanks for all the comments. Here’s a few of the pieces I have underneath the shears. These are now around 9%, do they have the pith or will it split later on? Sorry for the poor Pic, only one I have right now.

View bigblockyeti's profile

bigblockyeti

5779 posts in 2137 days


#13 posted 10-26-2018 04:09 PM

These are of a red oak mantle that was air dried and the pith has created problems. It is 11 3/4” x 4 1/4” and was felled and milled ~ 7 years ago, dried and installed 4 years ago. It has continued to dry over the past 4 years and shrunk nearly 1/4” during that time. The inadequate drying time aside, the inclusion of the pith has only made things worse. I did not do this one but have used air dried red oak with the pith in the past without problems, but it was allowed to air dry for 7 years before planing sanding and finishing.

-- "Lack of effort will result in failure with amazing predictability" - Me

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