On 2010-04-09, DoN. Nichols wrote:
On 2010-04-07, Ignoramus17356 wrote:
I need to drill some 21/32 holes with a hand drill, not accessible to
drill press.

I do not have a reduced shank 21/32 drill bit and new they cost $30+.

[ ... ]

I thought I could reduce a shank of that drill bit by simply chucking
it in a lathe and taking off some diameter with a carbide tool. What
are the drawbacks, if any, of doing so?

Typically -- you won't even need carbide. The shank of most
drills is mild steel, joined to the HSS for the working end. This is so
the chuck jaws can dig in a bit to get a better grip.

If you have to clamp it in the lathe chuck on the flutes (the
shank is too short), what I would suggest is getting a length of copper
1/2" tubing, slit it along the length, and slide it over the flutes to
act as a sacrificial surface to clamp on.

And next time a surplus lot gives you a batch of Silver &
Demming drill bits (the reduced shank ones) remember this, and instead
of putting them on eBay, save them for your own needs. (I suspect that
you have already had and sold more than one set. :-)

I actually have quite a few of S&D drills, but not in 21/32.

I regret selling a lot of things... But I am space limited.

i