Brian Lawson wrote:
Hey Bob,

Got one on a "sensitive drill press" gadget.

Ah, "sensitive" is a much better adjective than "precision".

....
Chuck has 23 teeth, Jacobs KEY 0 has 11 teeth. ...

It's nice that you and Ned agree - could get ugly otherwise G.

Key guide pin diameter is .153 long and .1235 diameter (I will get out
the pin gauges and check the chuck holes if you want, but I assume
they are 1/8")

No need to check, thanks anyhow. The Jacob's spec is .125.


...
Major diameter of Key "barrel" just above teeth is approx. .440
Not real sure how to measure easily, but across one tooth and one land
at the minor diameter I get approx. .334

Thanks - that looks like a good match to my chuck.


If this isn't enough, grime a shout and I'll dig deeper,

Oh, this is enough, for sure.

but I note that KBC Tools has

SKU # 1-508-03505 JACOBS K0 CHUCK KEYS $4.75 ...

Thanks. McM-Carr has them too ($2.13), but I might feel compelled to
order some other stuff.

Thanks again - I'm off to mcmaster.com

Bob