Delta TS top not flat

I have a Delta Contractors TS -- made in the USA -- probably from 96-97. I'm the original owner.
It seems the top is slightly rounded from front to back. When I lay a staightedge across it, it "rocks". I've tried pulling the center down, by shimming the front edge. It helped some. It's out of flat by .010 to .020.
I guess front to back is better than left to right.
Any suggestions? It's noticeable when I butt up the "more flat" right wing table. If I get it level at the front and back, the TS top is above the wing in the center.
Any suggestions?
PS I alligned the blade to slots, and am within .003 using the same reference pt on the blade from front to back.
I thought runout was very impressive .001
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How do you know the "straight edge" is really straight? If it isn't, then any measurements are probably suspect. Especially when the measurements are very small.
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wrote:

assuming that the straight edge is a quality piece, it came from the factory straight and with the 2 edges parallel. over time and use they can (ad do) get bent, warped and worn. wear is pretty easy to spot visually at the amounts relevant to woodworkers. to check for warp make your measurement, flip the straight edge over (not end for end) and check again. compare the results....
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That is if the straightedge isn't straight but on one side only. I have one straightedge that is fairly accurate, but only on one edge and not the other. This is how it is machined. However, my Starrett straightedges are straight and parallel on both sides to an amazing degree of accuracy.
Some people say you don't need one that accurate, but I found one time I was compounding the innacuracy by using a "good" straightedge. I was cussing how far the jointer tables were out until I got out my Starrett. I then found out it was only out a little. The rest was the straightedge.
Preston

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