How flat is flat enough?

[Larry Feltner]

I am trying to build a sugar chest out of cherry. I milled all of the boards that I'm going to glue up for the sides. They all stayed pretty much dead flat except for one that cupped slightly. I'm thinking about milling another one to replace it. I think I have enough stock. My question is how much does a board have to twist or cup before you will toss it aside and replace it with something else. Nothing will ever be perfect, but this has probably cupped so that the edges are 1/16 - 3/16 off of a flat table. I can't plane out the cupping because the board is already at final thickness. Would you try to work with this or replace it? How much error is too much error?

[Paul Grant]

3/16 !!?? not a chance. Wood is not a perfect material but trying to force things will only make for a frustrating build. I typically buy 30 to 50% more material for a project (depending on my supply in the shop already) It allows to select boards that work with each other nicely, allows for mistakes, and the next project will be already partially supplied.

[Peter Aeschliman]

Yeah, if possible, I try to mill my stock to within a 1/4" of final thickness first, stack it for a day or so, then come back and mill it to final thickness just before I use it.

It doesn't always work out that way in reality... but at 3/16", I would set it aside and use another piece.

[Myk Rian]

I had a box top warp so bad I made a new one. After finishing the new, the old straightened out. (shrug)
Give it a day or 2 and see what it does.