Ed Huntress wrote:

Ed Huntress wrote:
John Doe wrote:

Assuming the drill needs to be held against the bicycle's bottom
bracket anyway, a non-locking connection turns out to be easy. Lowe's
sells 1/2 inch 20 TPI nuts in their specialty drawers (2 for $1.67).
That nut fits on the DeWalt drill spindle. The bicycle bottom bracket
tapered spindle is about 1/2 inch square. So a 1/2 inch drive socket
that fits the drill spindle nut neatly completes the connection.

I might carefully grind a little bit off of the bottom bracket square
tapered spindle and/or maybe the socket drive area so that the 1/2
inch drive socket slides on a bit further, if I can confidently do
that. Don't want to make it off-center though.

Aha. It sounds like you're trying to lap-in the bearing cones on the
bottom bracket, right?

That should be "cones and cups." I have done this with bicycle wheel
bearings, but that was in my engine lathe.

https://farm8.staticflickr.com/7665/...ec9d50e7_z.jpg

A 1/2 inch drive socket pushes onto that but only about 3/16 of an inch.
Would be useful to shave the four sides of that spindle and/or the inner
square drive area of the socket, so that the socket will slide onto the
spindle further, but only if it can be done without misalignment. A tiny
bit of wobble would be okay, but only tiny.