An upcoming project will have me making 8 different M1.25 spur gears to
replace missing change gears for a lathe that seem to be unavailable
from the manufacturer. I've got a set of gear cutters on the way from
China and I've been reading up on the machining process so I think I'm
good there. What I need to do is figure out the best steel to use so I
can order a chunk of bar from my steel supplier.

I don't have real heat treating capabilities yet, just your basic
Kasinit case hardening. The change gears in the lathe obviously don't
run 24x7 and don't carry huge loads generally so what steel would be
best and not overly difficult to machine? Is case hardening a good idea?
Presumably case hardening doesn't have as much warping potential as real
heat treating, and of course I don't have the capability of finish
grinding though I could perhaps rig up a fixture to run in the new gears
against each other with some lapping compound if that might help.

Thoughts? Suggestions?