Table Saw Setup Tolerances

Be reasonable — we're milling wood here, not machine steel. September 28, 2006

Question
I have a 3 HP Delta Unisaw. With the cast iron wings attached, what are considered acceptable height differences throughout the table? If I place an accurate straight edge (+/- .005 on 150") and use feeler gauges when all is attached, at worst there are a few places where the difference across the two wings and table top is .005, and other places are perfect. I've tried shimming the wings to get everything as close to perfect as possible but this seems almost impossible. What is considered acceptable tolerance for the entire table top? If I measure each wing and table top separately they seem to be very accurate. (.002 at the worst). So in theory I should be able to get the table almost .002. However I’ve had trouble getting this result and it’s getting frustrating. I’m wondering if it’s even necessary.

Forum Responses
(Solid Wood Machining Forum)
From contributor A:
I think you're going way overboard for a table saw. Just reasonably flat is more than acceptable. More important is how the joints line up. They need to be as flush as you can get them because this is where the scratches on your sheet goods are going to come from. I suggest filing the edges more than the factory bevel. Instead of a bevel, make it a nice smooth round over. This will eliminate most of the scratching that might otherwise occur.

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From contributor B:
PM allows a top to be within .015" as acceptable. I think you are getting too fussy.

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From contributor C:
You're not milling engine heads, you're milling lumber. I would be more concerned that the fence is perfectly square with the blade. I think your saw is fine. I wish mine was that good, but it wouldn't make any difference anyway.

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From contributor D:
What's the difference? It seems that if we are concerned about keeping the fence and blade absolutely square to one another then why does the table top not matter as much? It seems to me a table top out of alignment by more than .003 would cause as many problems as a blade or fence out of alignment by just as much.

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From contributor C:
If you are cutting a board on your saw 12 inches long at 90 degrees, .003 of an inch off square can not even be measured. If you could determine this, the wood will probably be .004 or .002 tomorrow. Precision in fine woodworking is most important, but not to the thousand of an inch. We mill our faceframe and door frames to within .005 thickness, but with a widebelt sander. Even if your saw table was perfect to .000 inches, the wood that you lay on it to saw is not. Like I said, you're not milling engine heads.