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How to take the cup out?

Started by locustoak, October 25, 2009, 08:02:22 PM

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locustoak

I was wondering if anyone has a trick to taking the cup out of a board.  I had a couple boards I had finished to 3/8" thick and 6 3/4" wide.  I left them sitting for a couple months since I had no time to finish my project.  I take a look at them again now, and I see that they have a slight cup to them now.  Nothing too serious, but it would be noticeable on what I'm making.

Tom

Sometimes you can dampen the concave side and let it sit awhile.   Most folks rip the board into smaller strips, flipflop each one so that the cup is alternately on each side,Glue them together, and then plane it flat.

Lud

A bit of weight  on it after you wet it like Tom said?  Or put them face to face and clamp down over the length with cauls?
Simplicity mill, Ford 1957 Golden Jubilee 841 Powermaster, 40x60 bankbarn, left-handed

Don K

I have seen pros like Norm Abram make small relief cuts on the back of the cup and it will allow the board to flatten. Works good if the cuts will not be seen.

Don
Lucky to own a WM LT40HDD35, blessed to have a wife that encouraged me to buy it.     Now that\'s true love!
Massey Ferguson 1547 FWD with FEL  06 GMC Sierra 2500HD 4X4 Dozer Retriever Husky 359 20\" Bar  Man, life is getting good!

Don_Papenburg

With 3/8 it would not take much to flatten .  Clamping is a good way to do it without destroying the boards. May not have to wet the wood .   Clamp to a flat surface or back to back use a lot of clamps.
Frick saw mill  '58   820 John Deere power. Diamond T trucks

logwalker

Drying the convex side works for me. Expose it to a heat source or the sun in summer and monitor it. A thin board will move in a day or two. Joe
Let's all be careful out there tomorrow. Lt40hd, 22' Kenworth Flatbed rollback dump, MM45B Mitsubishi trackhoe, Clark5000lb Forklift, Kubota L2850 tractor

IMERC

Quote from: locustoak on October 25, 2009, 08:02:22 PM
I was wondering if anyone has a trick to taking the cup out of a board.  I had a couple boards I had finished to 3/8" thick and 6 3/4" wide.  I left them sitting for a couple months since I had no time to finish my project.  I take a look at them again now, and I see that they have a slight cup to them now.  Nothing too serious, but it would be noticeable on what I'm making.

expose the convex side to the sun...
monitor closely.. you mave to dampen the convex side a bit.....
Who ever invented work didn't know how to fish.... Here fishy fishy....

logwalker


Quote from: IMERC on November 01, 2009, 11:58:03 PM
Quote from: locustoak on October 25, 2009, 08:02:22 PM
I was wondering if anyone has a trick to taking the cup out of a board.  I had a couple boards I had finished to 3/8" thick and 6 3/4" wide.  I left them sitting for a couple months since I had no time to finish my project.  I take a look at them again now, and I see that they have a slight cup to them now.  Nothing too serious, but it would be noticeable on what I'm making.

expose the convex side to the sun...
monitor closely.. you mave to dampen the convex side a bit.....


Do you mean dampen the concave side? Joe
Let's all be careful out there tomorrow. Lt40hd, 22' Kenworth Flatbed rollback dump, MM45B Mitsubishi trackhoe, Clark5000lb Forklift, Kubota L2850 tractor

IMERC

yur gonna make me try this tomorrow ain'tja...

now I'm not so sure...
Who ever invented work didn't know how to fish.... Here fishy fishy....

IMERC


Do you mean dampen the concave side? Joe


yur right....
sorry about that...
what could I have been thinking of...


so busted as I slink away....
Who ever invented work didn't know how to fish.... Here fishy fishy....

logwalker

Don''t beat yourself up. you were trying... ;)
Let's all be careful out there tomorrow. Lt40hd, 22' Kenworth Flatbed rollback dump, MM45B Mitsubishi trackhoe, Clark5000lb Forklift, Kubota L2850 tractor

cpkstudio

With a board as thin as 3/8 a few simple braces on the back side of the wood will flatten it out and keep it flat even after it is integrated into the piece.  This of course would only work if you were using the board in an application where the bracing would not be seen.  I would be concerned that it would warp again without being braced even if you get it flattened prior to installing it.

locustoak

Thanks for the help everyone!  What I ended up doing was putting the peice beside the wood stove, and I let the heat bend the board for me.  I let it sit beside the stove too long the first 2 times and it started cupping the other way.  I eventually got it right.  It was only 14" x 7" x 3/8", so it was easy to do.

ljmathias

Sure hope it works long-term: I'd be worried about it re-cupping with humidity or moisture contact.  Keep us posted on whether it stays "uncupped" for you.

Lj
LT40, Long tractor with FEL and backhoe, lots of TF tools, beautiful wife of 50 years plus 4 kids, 5 grandsons AND TWO GRANDDAUGHTERS all healthy plus too many ideas and plans and not enough time and energy

DanG

I'm bettin' it will stay flat if both sides have equal exposure to the atmosphere.  It probably cupped because one side was exposed and the other was not.
"I don't feel like an old man.  I feel like a young man who has something wrong with him."  Dick Cavett
"Beat not thy sword into a plowshare, rather beat the sword of thine enemy into a plowshare."

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