On Dec 24, 12:08*pm, Doug White wrote:
I need to drill a clearance hole for a #8 bolt (0.165" dia) through ~ 1
1/4" of 6061-T6 aluminum. *The first half is well inside the material,
but the last 3/4" needs to be close to one outside wall of the material.
...
Doug White

When I was making RF enclosures I found that 0.020" to 0.030" was a
reasonable minimum wall thickness for small tapped holes. 0.015" was
usually enough for small drilled holes, if a pro machinist drilled
them in a Bridgeport. I never could get that close in a drill press.

Try a parabolic drill bit close to or at the finished size. If it's
important I'd practice on scrap and measure the deflection.

jsw