Which way is a board more likely to cup?

[CatButler]

I started work on a leg vise (single screw in the center) for my bench. The chop is a made from a piece of 2x8 SYP. Sadly one face runs almost exactly through the pith of the tree. If the board does cup, I want the edges to move toward the face of the bench so they will compress to squeeze the whole board rather than at just one point if they cupped away. Which way will it most likely cup toward the pith or away?

 

[cpowell]

I started work on a leg vise (single screw in the center) for my bench. The chop is a made from a piece of 2x8 SYP. Sadly one face runs almost exactly through the pith of the tree. If the board does cup, I want the edges to move toward the face of the bench so they will compress to squeeze the whole board rather than at just one point if they cupped away. Which way will it most likely cup toward the pith or away?

Should cup away from the center.

Linky: http://thewoodwhisperer.com/avoiding-cupped-panels/


Chuck

 

[Joe Scharle]

It'll cup toward the center of the tree, so place the inside of the 'tree' toward the other jaw.
I hope that's more clear than it now looks :wconfused:

 

[Bill Clemmons]

If you look at the growth rings in the end of a board, think about which way the board would have to move in order to straighten the growth rings out. That's the way it will cup.

Bill

 

[LeftyTom]

Now I am confused. :icon_scra By my way of thinking :eusa_doh: Bill and Joe do not see the board cupping in the same direction. :help:

 

[DWSmith]

I believe they both said the same thing, just different ways. The growth rings will always try to straighten out to flat.

 

[CrealBilly]

Depends on the "cut of wood"... Quarter and Rift don't cup hardly at all. Whereas, flatsawn cups most of the time. Here's a little visual aid to help you understand better.

 

[Gofor]

My experience has been that flat sawn boards (the bottom example in Jeff's visual aid) tend to cup to the outside of the tree as long as the surrounding moisture is the same on both sides of the board. By that I mean that the edges curl towards the outside of the tree, away from the heart. I have seen this with red and white oak, black walnut, yellow pine, sweet gum, and especially treated lumber.

I think this is because the wood shrinks more along the circle of the growth ring than it does across the thickness of it. Therefore, the longer growth ring (the outside most one) will shrink more than the shorter inside ones, pulling the edges away from the tree's original center. The smaller the tree, and the closer to the center that the board was cut, the more the amount of the cupping.

JMTCW

Go

 

[richlife]

The real answer is: Whatever way it wants! :wconfused:

I do agree with what has been said, but after laying hundreds (perhaps thousands) of boards, I think my answer is the "right" answer.

Rich

 

[CarvedTones]

The real answer is: Whatever way it wants! :wconfused:

I do agree with what has been said, but after laying hundreds (perhaps thousands) of boards, I think my answer is the "right" answer.

Rich

In the case of deck boards, the outside edges always cup up so it can catch water. Heaven forbid it develop a natural crown and shed water. :rolf: