In article , madw5
@verizon.net says...
I have to drill a number of flat bottom holes, 7/8" diameter and 1/10"
(.1") deep in some 2/10" (.2") thick aluminum. Is there a source for
flat bottom drill bits of this size that will fit in the 1/2" drill
chuck that's on my drill press? If there are no bits of this size with
a turned down 1/2" shank, can an adapter be purchased to go from the
7/8" bit to the 1/2" chuck? Thanks for any help. Marty


If you can live with a small (say 1/4" dia) deeper hole in
the middle of the 7/8 hole, you would probably have better
luck with a piloted counterbore.

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It's not too difficult to grind a flat bottom drill, but
unless you have a very rigid machine to run it, it's going
to push the work all over the place. An end mill that large
won't be much better.

Ned Simmons