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View Full Version : How flat does a workbench top need to be?



Perry Schmidt
02-19-2003, 12:19 PM
Working on a workbench top. It's basically done, and I'm flattening it w/ a hand-plane now. How flat is 'perfectly flat'? I practiced on the bottom side and could get it to within .009" w/ a very good straight-edge across the top.

Is that flat enough for a bench top?? Is 1/64" (about .016") flat enough since the top has a couple of very 'challenging' spots?

Thanks,

Officially switched over from Badger-Pond-Perry

Dave Anderson
02-19-2003, 12:32 PM
Hi Perry,
I think that 1/64" is pretty darn close. If it comes down to a "Zen" thing you could keep going and strive for .001 but IMO that's overkill. I'll assume that you are talking about 1/64th total difference over the length or width of the top or you may have some dips in the middle that are a 64th off.

What is the spec tolerance on your table saw? It's probably .010 across a smaller surface than your bench. Your bench doesn't need to be any more accurate than that.

Have you tried winding sticks instead of a straight edge to check for flatness? There are a lot of straight edges that aren't very straight. The human eye is one of the most accurate measuring devices on the planet. Try using winding sticks and your eye to judge for bulges or dips. I think you will get more accuracy that way.

Good luck!

Perry Schmidt
02-19-2003, 12:56 PM
Thanks Dave - useful info.

I haven't used winding sticks on the bottom but was planning on doing so on the top side.

I'm not trying the 'zen' thing by any means. And I guess that's what I was 'comparing' it to was a table saw top and wondering how close you really have to come to that sort of flatness. My table saw top is pretty flat. Don't know if that's the norm, but it's the only thing I've had to compare to :)

Thanks for the info.

Perry

Ken Salisbury
02-19-2003, 12:58 PM
At least flat enough so the Bud Light doesn't fall off of the edge.<

Dennis McDonaugh
02-19-2003, 1:16 PM
It needs to be be flat enough that you can glue up a chair or a small table on it so it doesn't wobble because one of the legs is out of alignment. I think .009 would do that for you. My bench top warped badly and I had to use a scrub plane to get it nearly flat. Then I used a #5 to smooth it. I don't have a good machinist straight edge so I used a jointed board and its "pretty" flat across the top and end to end, but I don't think its .009".

Phil Hudak
02-19-2003, 1:23 PM
Just make it flat enough so that you aren't fighting dips in the bench when squaring and assembling your projects.

I have 4' x 6' assembly bench in my shop; the top is a couple of sheets of termite barf edge-banded in maple - flat, flat, flat. :)

I can't tell you how much easier assembly is compared to when I was using sawhorses or folding tables with tops shaped like a potato chip. I would spend half of my time shimming the work to keep it square. :(

Phil Hudak