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Safe RPM for cast iron bearings?

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

Reply to
Aaron Kushner
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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

Aar> I have a Seneca 9" lathe with cast iron bearings. The countershaft

Reply to
Grant Erwin

Are the bearing journals "superfinished" like the SB lathes are? That might make the difference.

Ken Grunke

Reply to
Ken Grunke

My lathes spend most of their time below 500 anyway. (even though they go much higher) I use HSS toolbits most of the time and everybody is happy.

Use it for a while and I bet you won't find it to be a big issue.

chuck

Reply to
Charles A. Sherwood

Not sure what superfinished means. The journal bearings are shiny and the handscraping marks are still visible.

Not sure how the South Bends work, but this lathe has an oil sump and a ring that spins around between each set of bearings that distributes the oil around.

And to reply to Grant... Yes, I've been getting good and grinding HSS bits ;-) Is one size more appropriate than an other? I'm using 3/8" Rex AAA bits that I bought on ebay. Would smaller (5/16" or 1/4") bits be better for this size lathe?

Reply to
Aaron Kushner

I'm sure those bits are fine. They have one real good thing going for 'em, you've ALREADY PAID FOR THEM! :-)

I use a lot of bits in my shop. I recently needed a 3/16" square bit and sure nuff there was a new one in my "bit bucket". Bits that fit your toolholders are sure nice. I'm sure you've noticed that the part that does the work is pretty small, and once you've done the main grinding you can touch it up for quite awhile with a hand stone or one of those DMT diamond matrix stones (those are great). Bigger bits are of course more rigid so they can be extended just a little more, and smaller bits grind more quickly because there's less material to remove. - GWE

Reply to
Grant Erwin

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