Over tightening the nut is the most common issue. The arbor is threaded so
that when the saw is spinning the nut self tightens. You only need a few
ounces of force on the wrench. In the olden days blades were made from thick
plate. Today's premium blades are made from better thinner steel. If the
blade is flat, use a steel straight edge across the blade to check, then put
it back and don't tighten it as much.
max

I have a 10 inch Freud table saw blade that is very warped, or bowed, to the
point where I can't rip anything if the blade is fully raised because it will
bind terribly between the rip fence and the center of the blade. If I lower
the blade to 1" it rips smooth as butter, and when I miter cut from the other
side of the blade it is similarly smooth, sharp and aligned. If I raise the
blade fully and measure flatness of the blade half-way between its center and
its outer edge, there is a 0.015 runout or bow. So instead of being flat, the
blade is more like a bowl. I'd like to know why this occurred and have 3
ideas, but am not sure which (if any is true):

1) The blade sucks, never was flat, and I need to spend $100 to get a real
blade.
2) I overtightened the arbor nut and introduced the warp into the blade. I
did
tighten it probably too tight, not wanting it to loosen during use. And when
I
removed the blade, the warpage definitely lessened at least to the point where
the teeth made contact with the table when resting flat on either side.
3) My arbor washer is incorrect for the arbor on my unisaw. The diameter of
the arbor is 2.5" and makes contact with the blade only on its perimeter. The
diameter of my arbor washer is only 1 7/8". So when I overtightened the arbor
nut, the smaller arbor washer cause the whole damn blade to cup into the
arbor,
making a dish shape. Shouldn't the arbor washer be the same size diameter as
the arbor?

Thanks for any suggestions,
Greg
Greg