Correct on the top SB 9" speed. You may be able to simply put a 2-step
pulley on your motor. Max spindle speed and small spindle hole characterize
a lot of older lathes. That's why a lot of guys suggest you don't even
bother with carbide tooling, just get real good at grinding HSS bits.

If your spindle is built as heavily as the SB 9 and if it's lubricated
as well (and finished as well) then it should run close to a similar
speed. Given the uncertainty, however, I think I might not even try. Start
looking for a great deal on your next lathe and just go slower with this
one until you've found your next one, then sell this one and move on ..

GWE

Aaron Kushner wrote:

I have a Seneca 9" lathe with cast iron bearings. The countershaft
assembly has two pulleys, but the motor only has one.

The rpms are as follows:

direct: 558, 350, 222
back gear: 80, 52, 32

The max speed seems kind of low, but I'm not familiar with how
fast these lathes were designed to go. From reading the lathes.co.uk
pages, it seems similarly configured South Bend 9" lathes with cast
iron bearings went up to 1200 rpm.

I had the lathe running for 20 minutes at the top speed yesterday
and the bearing caps weren't warm at all.

So would it be OK to put a bigger pulley on the motor? And if so,
what should the top RPM be?

Thanks for any insight,
Aaron