Powermatic 90 motor change

[Jerry Ingraham]

I have an early seventies pm70 that I would like to convert to single phase. If I replace the motor, should I go more horsepower than the 1 hp currently in it? Is there any pros or cons to it?

[William C Rogers]

To answer your question yes, more hp. I would put at least 2 hp on it. I had a PM 90'that I sold earlier this year. When I first got it I changed the motor to a 1 hp single phase. That was about 7-8 years ago before VFD. If I was doing the same thing today I would get a 3 phase 2 hp with a VFD. At a 12" swing the 1hp was ok as far as hp. However speed control getting to low RPM was more of a problem. I raised mine to have a 18" swing. Now the 1 hp was really not ideal, but I got by. Not being able to get to a lower rpm was. My speed range was 350-2100 rpm.
Knowing what I now know I would get a 2hp 3 phase with a VFD. If I had done that I still might have the PM 90. But I decided to sell and I bought a Laguna 18-36, that I really like.

Raising the PM 90 is not hard or expensive. I spent less than $150 to raise it to a 18" swing, but had to buy new tool rest from Robust that cost another $200. You can find my process raising my lathe and others on OWWM site. I think I was the only one to actually extend the cast belt guard where others made one from wood. Note with the standard PM 90 tool rest you can only use about 16" of the swing because of length of the rest. Some bought tool rest from Oneway to utilize the 18" swing. The other thing I was going to do is bolt a 24" piece of angle iron to each end of the base to increase the base stance as the PM 90 is a bit top heavy. I believe the base is only about 16" and with an out of round blank it will rock a bit.

The last thing I want to mention is you can still get a lot of parts from Powermatic for this lathe. I bought new banjo clamp parts and new tail stock lock parts from them. The PM 90'is a great lathe and if I had went with the VFD and 2hp from the start I might still have it. Again I really like my Laguna. Any questions just ask.

[Jerry Ingraham]

William,

Wow! Great response. I got this lathe free and completely tore it down, replaced all bearings, cleaned and repainted. I left the 3 phase 1 hp motor in it and added a VFD. It was just kind of a hassle between the speed adjustment on the lathe and then the rpm control on the VFD but I used it that way for quite some time. The VFD has now apparently died and rather than replace it, I thought I'd just put a single phase motor in and do away with the VFD. I was debating even a 3 hp motor but I think I'll do at least 2hp.

The only reason I would get rid of this lathe is swing, so I'm going directly to OWWM to find your thread. If I could get it to 18" I'd be thrilled and keep it. Thank you very much for your response and I hope you don't mind if I come back to you with more questions!

Jerry

[William C Rogers]

William,

Wow! Great response. I got this lathe free and completely tore it down, replaced all bearings, cleaned and repainted. I left the 3 phase 1 hp motor in it and added a VFD. It was just kind of a hassle between the speed adjustment on the lathe and then the rpm control on the VFD but I used it that way for quite some time. The VFD has now apparently died and rather than replace it, I thought I'd just put a single phase motor in and do away with the VFD. I was debating even a 3 hp motor but I think I'll do at least 2hp.

The only reason I would get rid of this lathe is swing, so I'm going directly to OWWM to find your thread. If I could get it to 18" I'd be thrilled and keep it. Thank you very much for your response and I hope you don't mind if I come back to you with more questions!

Jerry

Jerry. Be happy to answer anything. You can PM if you like, I usually just look in the morning though. 18" swing is nice, I followed what Roy Turbett laid out with some differences.