On Dec 4, 5:23*am, "Buerste" wrote:

[regarding a nontightenable Jacobs type chuck;
the ring-gear sleeve is slipping on the nut]

... we used to repair them but it just isn't
worth it anymore.

But, for the edification of the original poster, it IS
instructive to disassemble and admire the internal
construction. Lightly knurling the inside surface of the
geared sleeve would solve the problem, and a
freshly lubed worn-in Jacobs chuck is SO smooth
in operation after a rebuild, it's worth the effort.
Unless, of course, you have paying customers waiting.

Jacobs offers takeapart instructions

http://www.jacobschuck.com/drill-chuck-repair.asp

Reassembly is easier if you heat the sleeve on a hot plate.