How flat for workbench top?

[Brian Elfert]

I bought a maple workbench top a few years back and never used it. Apparently, the back was unfinshed and it has warped so bad that there is a 1/2" gap in the middle. This top is basically scrap wood now.

So, I went out and bought another maple top from elsewhere. It is bowed too, and has at least an 1/8" gap in the middle. I'm thinking I need to return this one.

Am I expecting too much for a maple top to be reasonably flat? How the heck can I assemble things flat and square without a flat bench?

My dad has a 40 or 50 year old solid core door slab as a bench top. It still seems to be pretty flat after all these years, but I haven't put a straight edge to it to see if it is bowed.

Brian Elfert

[KYHighlander]

Take it back, take your straight edge with you and check them all before you take the heavy thing home. I am building a bench at the moment and that top must weigh 150 lbs.

[John Grossbohlin]

You are correct to assume the top should be flat (i.e. no twist, cup, etc.) to be of good use... The 1/2" gap one could probably be ripped in half, the edges jointed, and then glued back together to remove a lot of the cup. Then it could be planed flat. I'd determine if there are threaded rods or through bolts in it first! The 1/8" gap one could be planed flat.

It might be worth tying to straighten the tops out by removing the finish and then using moisture and the heat of the sun. Once flattened and planed then seal all sides to help keep it flat.

BTW, I've got a thick 30"x60" maple top that is very flat. I wouldn't be surprised to find out it was 40+ years old. It's original life was in an IBM facility that opened in the late 50s... I've had it for about 20 years as best I can recall.

John