Spindle Speed Leblond 13" Regal lathe

Said lathe tops out at 500rpm. Circa 1947 vintage. It is being run on 3 phase power, and runs quite nice. I do own a VFD that I have yet to try. The gear head seems to run smoothly and no damage is evident.
How far might I be able to push the rpm? It has tapered roller bearings.
Itching to try carbide tooling because of the convenience. At this slow rpm the surface finish is god-awful. Maybe I should simply stick with HSS or change to HSS inserts?
Any/all advice appreciated.

Ivan Vegvary
Sandy, Oregon

I have a a LeBlond Regal brochure (Bulletin R-111) from that era that states:

"Speeds shown (25-500 RPM) can be increased to range from 37-750 r.p.m. for Tungsten Carbide Tools."

I use carbide insert tooling on mine. One thing I learned is that in the context of carbide, you need to look for inserts specified for finishing. In the carbide world, finishing is .020 - .080" depth of cut.

My 13" Regal is over-driven to 650 RPM. With finishing inserts, I run at max RPM and Max Feed in Fine Range (.018 ipr). I get good finishes, but sometimes struggle with getting the chips to break since I can'f feed fast enough for the chip breaker geometry to work properly.

Note on these lathes, the Feed Compound Lever has a tag that states you can only use Course Range Feeds at 100 rpm or less.

To Lowe Buck,
Thank you so much for your thoughtful response. I will push it to 650 RPM and do studying about inserts. You provided me with confidence to investigate further.

I have a 17" Regal round head (probably 50's?) and my top speed is 614 rpm, so I wouldn't consider 650 really "pushing it". I've had the same idea of using a vfd to crank it up faster, but most of what I do is large diameter these days, so no need.

Also, I've been using a tool with ccgt inserts (high pos rake) that works great even at lower speeds. Has inserts for steel and high polish one for alum, got it from exkenna, who posts on this site. Lathe inserts .com

Just remembered I'd asked about this a while ago: can I speed up Leblond Regal 17"

If you increase the speed, be sure to keep watch on the hear of the casting. It should not go above 130 to 140 F. Or to hot to lay your hand on it for more then a few seconds. I saw a machine once that was a 500 rpm machine and the owner bought a electric motor that doubled the speed. He ended up ruining the Timken's and then made the mistake of putting class 3 bearings and totally screwed up the machine. I told him to junk the machine.

To Richard Newman,
Thank you for the link where this already had been discussed. What a wealth of information. What a group of wonderful machinists.

Ivan Vegvary
Sandy, Oregon

don't overspeed your lathe beyond manufacturers recommendations.
use appropriate tooling...either HSS sticks or carbide, and for the carbide call here, the man knows his stuff.(edit- I see that was already mentioned)
Lathe inserts .com

I am of the opinion HSS inserts are a waste of money, if you are going to shell out that kind of money might as well use the right carbide and get the benefit of specific geometries and chip breakers.

Ya, I know someone is going to say you sharpen them by rubbing the face, but what does that do for the flanks???? Those wear too, and you still got no chip breakers.

Call me a curmudgeon.

My take-away from the that older discussion is that the berings can handle higher speed, it's the feed train that might suffer. But if you speeded up the spindle and kept in the low feed range, seems like it should be ok.

But as I said, I just haven't found it necessary, I get good results as is. I do have a little South Bend 9A for really small stuff, nothing to boast about, but I can manage just fine.