Another Panel Problem

[Ron Robinson]

I had been following the recent thread started by Mr. Peacock concerning a glue-up that was not flat when the following happened to me. Being a relative novice I need some help figuring out what went wrong.

I'm making a night stand to be used as a telephone table. The plans are in Woodsmith, the stand is made of cherry ply with a base and top made of solid wood. The top and base are to be dyed darker than the cabinet. Anyway...

This is the top. 20" x 19". I started with 4/4 rough cherry that had been in my shop for more than a month. Jointed faces and edges, planed to 3/4", and glued up four boards about 5 1/4" wide. No biscuits, just edge to edge.

The panel after glue-up was good. Pretty flat with just a slight misalignment of one board. I sanded the panel with my belt sander on one side only with 150 grit. I then had to go out for a time (about 4 hours) and when I got back the panel was cupped so much a straight edge placed across the boards had a gap of more than 1/16" under the center. The growth rings were alternated.

Is this stress relief or a moisture problem? What did I do wrong?

Ron Robinson

[Jamie Buxton]

A sixteenth of an inch of cup across a 20" top isn't a problem. When you fasten it to the rest of the carcass, it will get pulled flat. In the long term, it is the rest of the structure which ensures that the top stays flat.

[Steve Clardy]

Not a problem. It will pull down when attached.

[Ted Shrader]

Ron -

As the others said - no problem.

What happened? If it was laying flat on a work bench top or something, one side absorbed a little more moisture than the other. It should return to flat after the wood stabilzes again. Your top was only trying to give a little lesson in wood movement. ;)

When you attach the top, make sure one set of screw holes through the top dust panel are enlarged to allow for seasonal movement so the top won't crack.

Ted

[Michael Adelong]

I started with 4/4 rough cherry that had been in my shop for more than a month. Jointed faces and edges, planed to 3/4", and glued up four boards about 5 1/4" wide. No biscuits, just edge to edge.Ron Robinson

Hello Ron,

I've been woodworking for about 1 year. I'm a veteran of exactly 1 glued up oak tabletop (it did come out flat), so I'll pass along one thing that I learned. Whenever I need to take more than 1/8" off of the thickness of a board, I try to do it over 2 evenings if possible. In your case, I would have jointed & planed them to about 7/8" and let them sit for a day or two. If they twisted or bowed after that, I still have enough wood left to joint & plane to actual thickness on the second day. If there is a lot of movement, I might go to 13/16" and let them sit yet another day. If they din't move after going to 7/8", I just take the remaining 1/8" off on day two.

My wood supply is kinda newbie small, so I have to be a little extra careful with what I have. If I start ruining good (expensive) wood on a regular basis, I'm outta this hobby.

Good luck,
Michael

[David Rose]

Ron, I agree with the others. I just examined a top for a blanket chest that was glued up and sanded a couple of years ago. When I lifted off other componets (not laying directly on it, but stickered), I discovered a twist of about 1/2"! Ugh! I can't pull this out by clamping it down as it will be a hinged lid only held flat by bread board ends which will help 'some' with cupping but not the twist! Also, I need pretty flat to cut the dovetails to get the breadboard ends on. I noticed that the humidity was a bit higher than it normally was when I was spending more time in the wood shop. The lid got stuck behind the couch in the house for about two weeks. I just rechecked it with winding sticks and it is almost flat!

Also, anything that can slow moisture transfer unequally from side to side, will cause all sorts of things to show up. Things like laying on a bench for a couple of hours can do it. Finishing one side will definitely do it.

David



I had been following the recent thread started by Mr. Peacock concerning a glue-up that was not flat when the following happened to me. Being a relative novice I need some help figuring out what went wrong.

I'm making a night stand to be used as a telephone table. The plans are in Woodsmith, the stand is made of cherry ply with a base and top made of solid wood. The top and base are to be dyed darker than the cabinet. Anyway...

This is the top. 20" x 19". I started with 4/4 rough cherry that had been in my shop for more than a month. Jointed faces and edges, planed to 3/4", and glued up four boards about 5 1/4" wide. No biscuits, just edge to edge.

The panel after glue-up was good. Pretty flat with just a slight misalignment of one board. I sanded the panel with my belt sander on one side only with 150 grit. I then had to go out for a time (about 4 hours) and when I got back the panel was cupped so much a straight edge placed across the boards had a gap of more than 1/16" under the center. The growth rings were alternated.

Is this stress relief or a moisture problem? What did I do wrong?

Ron Robinson