Don,

The design of this old lathe allow only 1mm. Changing internal gears
seems to be hard and time consuming. There's possibility using normal
feed but you must cut once.

Aha -- you are repairing an existing telescope. I would love to see
it.

Sure but now it is in pieces

The Bison is well known factory see:

http://www.bison-bial.pl/katalog/katalog.htm

With Kind Regards --jz.