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Forum topic by Deela40 posted 07-13-2014 01:17 PM 918 views 1 time favorited 18 replies Add to Favorites Watch
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Deela40

42 posts in 1832 days


07-13-2014 01:17 PM

Topic tags/keywords: ash bandsaw question resawing

I was using my bandsaw to resaw piece of ash. This particular piece, pre-cut, is 6” x 3.5” 1-1/4”. Once all the way through the two pieces bowed.

Any ideas of why this happened?


18 replies so far

View Clint Searl's profile

Clint Searl

1479 posts in 1106 days


#1 posted 07-13-2014 01:53 PM

Isn’t it obvious?

-- Clint Searl....Ya can no more do what ya don't know how than ya can git back from where ya ain't been

View Deela40's profile

Deela40

42 posts in 1832 days


#2 posted 07-13-2014 02:00 PM

Clint,
This is the first time I have tried to resaw anything on my bandsaw so I am not very familiar with all the issues with this process. As a result, it is not obvious to me.

View Wayno1's profile

Wayno1

12 posts in 167 days


#3 posted 07-13-2014 02:22 PM

I am having moisture issues as we’ll at this time. I could be off base,but it looks like the “shell” is dryer than the “core”
Hopefully someone can post and help us both

View Chris Cook's profile

Chris Cook

165 posts in 1026 days


#4 posted 07-13-2014 02:28 PM

wayno nailed it, you released the balance of stress in this piece. The cut of the wood determines when this can happen.

-- Chris, “as soon as you come up with something foolproof, they come up with a better fool""

View TheWoodenOyster's profile

TheWoodenOyster

1032 posts in 680 days


#5 posted 07-14-2014 03:02 AM

There is no reason that would be obvious to anyone who hadn’t resawed before. Don’t feel bad. Good job responding like an adult.

To answer the question, there are internal stresses that are released anytime you cut up a piece of lumber, especially when you do an operation like resawing. As soon as you are done cutting, the board in a sense releases a bunch of tension and can bow itself, or for that matter unbow itself. There is nothing weird or strange about what happened there. That is pretty common with resawing. One thing to consider is waiting at least a day to actually work with resawn pieces as they can warp and/or bow a decent amount over the first 24 hours when they are cut. Let them move around for a day or two and then joint, plane, etc. You could even wait a week or so if you have the time.

As those above said, it could also have something to do with moisture, but I have always broadly categorized it as internal stress. It is possible that the internal stress is being caused by moisture.

Hope that helps. Good Luck

-- The Wood Is Your Oyster

View Loren's profile

Loren

7822 posts in 2392 days


#6 posted 07-14-2014 03:30 AM

It’s fairly common. Case hardening can cause that too
I think.

This type of distortion is one reason I feel all the hubbub
about 12” and higher resaw capacity is a bit much. For
thin woods like veneers and guitar plates, I guess 9”
or 10” is good if the source board is wide enough, but
for general resawing for furniture making I find setups
of less than 6” go faster, are more pleasant to feed,
less prone to compound (wedge shaped cuts) error
and don’t often cup so much you have to rip the
resawn board in half and reglue anyway to get a
flat board in a thickness close to what you were after.

You may be able to flatten those out a bit by stickering
them with weight on top, or clamping flat in such a way
that air can circulate around the faces of the boards.

-- http://lawoodworking.com

View pintodeluxe's profile

pintodeluxe

3551 posts in 1558 days


#7 posted 07-14-2014 04:51 AM

It is reaction wood. Every tree has some, and you will find a lot of it near the base of the trunk, or where branches exit the trunk. Basically there is tension built into the structure of the tree to resist gravity, wind, slopes etc. When we cut pieces free, the tension is released.
Green or improperly dried lumber is more prone to these problems.
Flatsawn lumber is more likely to cup over time than quartersawn lumber.

Good luck with it.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View Jim Finn's profile

Jim Finn

1741 posts in 1667 days


#8 posted 07-14-2014 12:35 PM

Good quote: “There is no reason that would be obvious to anyone who hadn’t resawed before. Don’t feel bad. Good job responding like an adult”.//// ////// I have had this problem when resawing oak that I stored outside. Bringing it inside to the workshop for a few days helps to acclimate the wood to the shop and this problem is lessened.

-- In God We Trust

View CharlesNeil's profile

CharlesNeil

1170 posts in 2615 days


#9 posted 07-14-2014 12:58 PM

The issue here is 2 fold, one you have released stress as stated, second no matter how dry wood is, its never as dry on the inside as the out side, so when you open it up, the newly exposed surface is going to dry out and as it does it shrinks causing it to cup. A trick I use is to lightly dampen the out side, then after its resawn clamp it , back to back with the new surfaces on the out side and let it acclimate a few days, makes a world of difference. You can probably also put these out in the sun for a little bit , with the OUT SIDE up , this will cause the out side to dry a little more and often it will reverse a cup, the key is to get the moisture in balance. Just be careful I have seen the sun totally reverse a cup .

View Redoak49's profile

Redoak49

465 posts in 733 days


#10 posted 07-14-2014 01:40 PM

As all of the above has said, it is really an expected reaction. Also, when you have the rings of the tree almost parallel to the surface, you can expect some bowing of the boards. If the wood is not completely dry all the way through, the bowing will probably get worse.

Plain sawn wood like this does have the tendency to bow while quartersawn wood will bow much less.

View Deela40's profile

Deela40

42 posts in 1832 days


#11 posted 07-14-2014 01:53 PM

Thank you all for the informative responses. I have clamped the two pieces together and will see if this improves the bowing after a few days.

View gfadvm's profile

gfadvm

11484 posts in 1435 days


#12 posted 07-15-2014 01:05 AM

Charles Neil nailed it (as usual). I would add that certain woods (pecan) is especially prone to cupping when being dried. Even when properly stacked and stickered with weight on the stack. I actually have more trouble with the boards near the center of the log (quarter sawn with pith down their center) cupping than the outer flat sawn boards.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View bigblockyeti's profile

bigblockyeti

1784 posts in 465 days


#13 posted 07-15-2014 02:14 AM

It’s case hardened as previously mentioned. It wasn’t dried correctly in order to prevent this.

View Deela40's profile

Deela40

42 posts in 1832 days


#14 posted 07-15-2014 11:29 AM

Is there any way to avoid this? If there is an issue with the drying process, how can I tell before I make the purchase?

View bigblockyeti's profile

bigblockyeti

1784 posts in 465 days


#15 posted 07-15-2014 12:54 PM

Taking a section from the end and cutting a section from the middle ~1/3 of the width, forming two prongs will revel the presence and severity of any case hardening. Hopefully the picture can explain it better than I can.

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