https://www.northerntool.com/shop/to...E&gclsrc=aw.ds

I use these tap drills. They drill, tap and countersink. Works great

If you can get to the backside, I strongly suggest through-bolts for them.

I like
masking tape
Philips screw driver
Can't thru bolt it, no access


counter sink, saw online larger diameter drill bit turning backwards.
thanks for all the ideas

Masking tape, countersink or chamfer with grinder.
Also measure 4 times!
https://cimg5.ibsrv.net/gimg/www.off...06fbbf0358.jpg

Holy Holes Captain.

PA.WOODCHUCK,

Take the drill bit you want to use to a local machine shop and ask if they can sharpen it "for brass". They'll know what to do. If you have a bench grinder and are at least somewhat handy with it, try it yourself. See .

Thanks. Brad.
Model Machine and Precision LLC
(937)545-8991

I would say your bit is a hair too small, and thus will encourage cracking or chipping. I recommend an 11/64–it will be plenty snug, with no danger of twisting off the head. I simply cover the area with some blue painters tape, and don’t put too much pressure on the drill, because you don’t want it to grab. I’ve installed tons of #10 screws that way with no cracking, but also no other special procedures (although I’m sure they may be effective). If you’re going to thru-bolt a #10, use a 3/16 bit. As others have pointed out, thru-bolting is always better if you can reach the backside without too much trouble.