16 years ago
variable-speed drill press has a minimum speed of 500 rpm, which was a
real problem, especially when countersinking.
I had found an interim solution for larger holes: Put the countersink
in the hole and turn power on, releasing the downward pressure before
the press gets up to speed.
This did not work with small holes, and the 1/4-inch severance
countersink, working in 6061 aluminum, flooded with a water-based
coolant. I would have thought that a small countersink would be OK at
500 rpm, but the holes became ragged and misshapen.
Countersinking with a hand drill did work, making pretty holes, but
yielded inaccurate countersinks because it's so hard to drill straight
I was busily tearing metal and hair when it occurred to me that tapping
is an extreme kind of machining, and yet one can get clean threads, with
the right lubricant. So I tried LPS Labs' "Tap-All". It worked, even
at 500 rpm.
Haven't tried it in steel and/or for large holes yet.