We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember (Graz) saying
something like:

In any event, I was under the misguided impression that all Jacobs
chucks were alike. The one that came off the drill had a half-inch
threaded stub attached, the one I was hoping to replace it with
didn't.

See if the stub unscrews from the chuck.
--

Dave