According to Norm Dresner :
I've got a (roughly) 35 year old AMT (American Machine Tool) bench drill
press that's still working wonderfully and although I've thought
occasionally of replacing it with a more modern DP with conveniences like a
larger table, a ratchet drive on the table and possibly even variable speed,
I still can't bring myself to part with this marvelous piece of machinery.

BUT ... I'd like to purchase a better chuck. Some of the drilling I do with
this beast is in the #70-80 range in both model working and PC board
manufacture and while I don't yet have the tool to measure the runout (it's
been ordered), I think that I need something with a little better precision,
even if a smaller range.

HOWEVER ... I don't think I've ever seen any product offered in the last 30
years for a JT#2-1/2. Is it a complete orphan or is something available?

I think that you're going to need two things to get there.

1) A truly accurate 1/2" chuck. (Does your drill press happen to
have a Morse taper in the spindle? If so, you can select other
Jacobs tapers than the JT 2 (which is more likely what you
have).

Good accurate chucks with little runout are made by Albrecht,
and *some* of the clones are of equal quality, while others are
not.

But -- none of these close down tight enough to grip much under
perhaps a 1/32" drill bit -- certainly not small enough to
handle a #70 or #80 drill bit.

2) A sensitive drill adaptor to go in that chuck. This consists
of a (typically) 0-1/8" Albrecht chuck mounted on a sliding
spindle which is chucked in the drill press chuck. There is a
ring just behind the chuck mounted to the shaft with a ball
bearing between them, which allows you to grip the ring and to
pull the sliding spindle down against a light spring in the
adaptor, so you can control the drilling pressure with these
tiny bits with at least some feel. The normal spider for
feeding the drill press's spindle will give you worse than no
feel for the drilling force, and will cost you a lot of tiny
drill bits.

An example of this sort of thing can be found in eBay auction
#7595222558. This one happens to only go up to 1/16" instead of
1/8" but should suffice for your needs.

This was found by an eBay search on "sensitive drill" (with
the quote marks -- without, you get thousands of hits, including
some eBook on "mastering premature ejaculation". :-)

This search also brings up some sensitive drill presses, though
only one looks like one that I would choose for serious work,
the one in auction #7596471948, though auction #8907848616 looks
interesting. It would need some additional equipment to power
it.

I, personally, have a Cameron Micro Precision drill press, which
works quite well for the purpose -- but I got it new back around 1973 or
so, when the price was a lot more reasonable. However, keep watching
the eBay auctions, as interesting ones come up from time to time. A
good sensitive drill press would be a far better choice for you than
trying to use an adaptor in a regular drill press. And -- it would let
you keep your regular drill press for normal size drilling. Among other
things, drilling in the #70 and smaller size range really needs a higher
spindle speed than you can coax out of most drill presses which were not
made as sensitive drill presses from the start.

Good Luck,
DoN.
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