Powermatic 90 wiring

[Matthew Bowman]

I have recently purchased a PM 90 lathe that has had the micro switch in the head bypassed and the motor directly connected to a power cord. The guy hat I bought it from was kind enough to provide me with a magnetic switch, but now I am left with the problem of figuring out how to wire the darn thing up... Does anyone have a diagram of how it is supposed to be wired?

Thanks

Matt

[M Toupin]

www.vintagemachinery.org has manuals, but save yourself the aggravation and just leave it as is. The micro switch is a real pain that's why the PO (and most PM90 owners) disconnect it.

Mike

[Thomas Hotchkin]

Matthew
Welcome to the creek. Have you looked inside the magnetic switch, quite often the manufacture had wiring diagram inside the switch box.

[William C Rogers]

www.vintagemachinery.org (http://www.vintagemachinery.org) has manuals, but save yourself the aggravation and just leave it as is. The micro switch is a real pain that's why the PO (and most PM90 owners) disconnect it.

Mike
Mike is right on the pain. I bypassed mine. Mine was a three phase and I converted it to single phase and I ended up just installing a relay on mine connected to the switch on the lathe. There are some manuals on line.

[Matthew Bowman]

Ya, the magnetic switch has a diagram on the inside. I guess I will just bypass the micro switch if it is not a big deal. Thanks for the advice :D that makes everything much easier.

[William C Rogers]

That micro switch just turns off power when speed handle is at lowest RPM. No big deal.

[Roy Turbett]

The micro-switch in the headstock is there to keep you from accidently turning the lathe on at full speed with an out of round blank which can be very dangerous. I have three Powermatic 90's. Two of them have 3 phase motors with programmable VFD's that are set so that it takes 5 seconds for the motor to accelerate to full speed. This gives you plenty of time to react if something goes wrong when you turn on the lathe so the micro switch isn't needed.

My third Powermatic 90 has a single phase motor that instantaneously goes to full speed and can't be slowed down. I kept the micro switch on this lathe for safety. As shipped from the factory, the only way to reduce the spindle speed is to move the speed dial to reduce the pulley ratio which can become a pain in the neck if you want to stop the lathe to check your work. The spindle has to be turning for the speed dial to move and it must be in the "Stop" position to start the lathe.

I suggest you visit OWWM.org and search Powermatic 90. You'll find a number of threads that detail how to rebuild and wire these lathes. I highly recommend that you stick with the original 3 phase motor and add a VFD. You'll find its about the same money as buying a new single phase motor. Also, Powermatic 90's that were made prior to October 1972 have the motor mounted in the lathe bed. This is an odd size motor because the wiring housing is opposite what you find on a typical 56 frame motor. If you have one of the older lathes, keep the original 3 phase motor and add a VFD.

[Roy Turbett]

That micro switch just turns off power when speed handle is at lowest RPM. No big deal.

What you say is true but the main thing the micro-switch does is it prevents the lathe from being started with the speed dial in any postion other than "Start". Most Powermatic 90's also have "Start" and "Stop" buttons. If the "Stop" button is pressed while the lathe is running, you must turn the spindle by hand while pulling the speed dial handle back to the "Stop" position to restart the lathe. The lathe is started by pressing the "Start" button while moving the speed dial to the "Start" position.

[William C Rogers]

What you say is true but the main thing the micro-switch does is it prevents the lathe from being started with the speed dial in any postion other than "Start". Most Powermatic 90's also have "Start" and "Stop" buttons. If the "Stop" button is pressed while the lathe is running, you must turn the spindle by hand while pulling the speed dial handle back to the "Stop" position to restart the lathe. The lathe is started by pressing the "Start" button while moving the speed dial to the "Start" position.



What you say is true, however by habit I always bring the speed down to the lowest setting before turning the power off even to check my work. Doing that I don't think I am any different in starting than using the micro switch. Yes, you must be more careful knowing the speed setting, but I always check the speed before hitting the start button. I tried to wire mine through the lever, but it was a pain and couldn't get it working properly. I don't remember why.