On Tue, 23 Aug 2005 20:05:56 -0400, Ol' Duffer wrote:
I have an exterior faucet with the threads grown up
with mineral deposits so that I can no longer get a
hose screwed on, and would like to chase the threads.

Have you tried a good scrubbing with something like CLR and a stiff brush?
Is there some reason that you can't replace this hose bibb? (It's usually
a fairly minor chore -- see Sept 2003 This Old House magazine.)