"stryped" wrote:

I layed a metal square on the table and could see light under the
middle. Did not use a guage to see how much.

What is the best way to determin if the table needs reground and how to
measure it?
If you are putting the straight edge on one table (not across two
tables or one table plus blades), it might need grinding. Don't worry
about small local depressions, such as minor rust pitting or small
areas where a previous owner might have gotten too aggressive in
rubbing out some rust, though.

Can any metal rule be used as a straight edge?

Good straight edges can get expensive. An inexpensive alternative is a
pair of plastic "draftsman triangles". I haven't used them, but
understand from others that these are generally very accurate and not
subject to warping. Sounds like the "lose out" in a comparison to
metal straight edges (to the tolerances of concern to a woodworker)
only in lack of durability.

Put two triangles "back to back" so that they form a larger triangle.
if there is a dip in the table, when the tops of the triangles touch,
there will be a gap at the bottom
--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.