cupping tabletop

[Frank & Renee]

Greeting!

I am a novice woodworker, and have made most of my projects on inexpensive pine. I recently decided to make a table that I found in Anthony Guidice's book "Tables". I recently bought and dressed about 25 BF of nice curly maple....but I still cant bring myself to use it until I am comfortable with what I am doing.

The project called for cherry, but I am using soft maple I got from a local ("reputable") lumber yard here in New Hampshire (again I went the cheap route). It was kiln dried 6-8%......... I let it sit in my workshop in the basement for a couple of days. I jointed and planed the 4/4 lumber down to

3/4" and glued up my top....making sure to alternate growth rings as I have read. I used (3) 8" wide pieces. The finished top will be about 20" square. I let it sit for about 24hrs clamped, and set it aside to be cut down later. a week later the damn thing has huge cup in it! there is about 3/4" gap between the table top bottom and the bench top. Did I not let it acclimate long enough? Should I have used four or five boards to create the top rather than the (3) I used? Any help would be greatly appreciated!!!

Thanks

Frank

[patriarch]

"Frank & Renee" wrote in news:zeSOc.1776$%J6.888@trndny07:

Now turn it over, and lay it on some narrow boards (called stickers), so some air can circulate around it. Some of that should go away in a day or two. Uneven drying is the likely culprit here.

If that doesn't take care of it, there are some other, more drastic things to look at doing. But try the simple first.

Patriarch

[George]

Good advice, and a lesson in how much the alternating growth rings business is really worth.

With luck, you'll get an acceptably flat project by equalizing adsorbed moisture, and then protect it by applying the same number of finish coats to both sides of the top.

"patriarch [e-mail]" "Frank & Renee" wrote in

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[Robert Bonomi]

_THIS_ idjiot always assembles wide surfaces from pieces no wider than 4". (and usually no less than 3" :) OTOH, for something 6", 7", or even 8" wide, I may well use a single piece. Consistent, ain't I?

That said, you've got 'something else' going on, to have caused cupping of _that_ magnitude.

I'd suspect that _where_ and/or _how_ you 'set it aside' for that week has a great deal to do with the situation -- uneven exposure to moisture and/or heat. quite likely in an older, unfinished basement.

[Edwin Pawlowski]

Couple of things I have learned: Never let a flat board sit on top of the table saw for a few days. Never set a flat board where it can hang off of the end of the bench a foot or two.

Standing a full supported board on glued up panel edge seems to be OK.

The above may or may not be your problem, but I know they have cause problems for me. Ed

[POP_Server=pop.clara.net]

"Frank & Renee" wrote

In the event of other proffered advice not working, Frank will need to deliberately weaken the underside by a series of parallel, long-grain grooves, each starting a small distance from an end.

The buttons or other fixing devices should then pull the top down against the underframe.

Jeff G

[Frank & Renee]

Good news,

I am beginning to understand that being patient is an important part of woodworking. I recently wrote about a severely cupped tabletop that I had recently glued up. I placed it on a few "stickers" as suggested by a fellow member of this group, and after 5 or 6 days the tabletop is almost completely flattened out!! I was really close to cutting it up an starting over!

Thanks again!!