replacement motor for 3520b

[allen thunem]

Working in the shop yesterday and started hearing bad sounds emanating from the motor of my 3520b.
Question for this owners who have had to change out their motors on this lathe.
Did you go to powermatic to replace it?? would imagine this is the most expensive avenue to take.

are their aftermarket motors out there? and if so what did you get??

can i upgrade to a a 3 hp motor without changing the vfd??
am sure its the motor so not looking for diagnostic assistance here just info on replacement options

[Hayes Rutherford]

Allen, I don't know what other motors would work. Just be sure its the motor and not something else. If it is the motor maybe you are covered by warranty.

[allen thunem]

what did you find to be the problem??
i will keep you in mind hayes

[Mike Goetzke]

Allen - My new 3520B had a noise from the motor when it was under warranty. They sent a replacement and didn't want the old motor but had me prove I destroyed the nameplate. Anyway, I tore into the old motor after buying replacement bearings. The only other motor I rebuilt was a "bullet" motor for my Unisaw and this PM motor is super simple - no brushes! Don't know if this is your issue but I found lots of paper thin casting flash left on the motor cooling fins. Some of this debris got into the bearings and created the noise I heard. I used sealed bearings and cleaned up the casting and the old motor runs better than new.

You may want to do the same with your motor.

(Oh - forgot to mention, based on forum suggestion I bought one of those $4 mechanics stethoscopes to determine it was a bearing.)



Mike

[Joe Kaufman]

Keep in mind that the long output shaft of the 2 HP motor will make a reasonably priced aftermarket motor highly unlikely. The 3 HP from the PM's big brother has a shorter shaft. The VFD also over drives to about 135 hz., again not a trivial issue with an "aftermarket" motor.

[Hayes Rutherford]

Allen, my problem was the bearings. Before I put the new one in, I decided to take it apart and found the output end bearing was bad and replaced both. Problem solved.

[Bob Hovde]

I took my motor to a local electric motor repair place and they fixed it like new for about $100.

[Bill Boehme]

About the only things that will cause noise on a three phase AC induction motor are the bearings. Replacing them is easy and it won't cost very much. Don't make the mistake of getting "better" bearings (such as bearings that have tighter clearance specs or different type of shields or seals. Motor bearings (at least on industrial motors) are single shielded (open on one side and a metal shield on the other). If the new bearing is open and comes unlubricated, you will need to use Mobil Polyrex EM grease or equivalent to fill it no more than 50% full. Do not use any old grease such as what you might find at an auto parts store for wheel bearings. Read this info sheet on Mobil Polyrex EM if your new bearings are not already greased.

To answer your question about going with a three horsepower motor, you will also need to get an inverter rated for three horsepower. It may be possible that you could use the same inverter if you programmed it to operate in "variable torque mode" rather than "constant torque mode", however, I can assure you that is an unsatisfactory option because you will not have any low speed torque.

[Reed Gray]

When the bearings went out on my 3520A many years ago, I bought the bearings locally, a new belt, and had them replaced for less than I could buy the parts for from PM.

robo hippy

[Roger Chandler]

If you decide to go with a new motor/inverter, the Delta Electronics "M" Series inverter is rated for 2 hp to 7 hp and is what is on the new 3 hp Grizzly G0766, which is supposed to be a fine inverter, from all information we can find........

[Mike Goetzke]

If you decide to replace the bearings yourself I have had great luck with Accurate Bearing.

[allen thunem]

thanks everyone
priced a new motor from pm almost 5 bills
will dig deeper into it today to resolve the issue but replacing the bearings might be prudent anyhow, just for piece of mind and it will give me something to do besides

[Brian Myers]

If you decide to replace the bearings yourself I have had great luck with Accurate Bearing.

+1 for Accurate Bearing , excellent service and excellent products . Excellent prices on Nachi and NTN bearings , just say you don't want any Chinese made bearings and they will deliver.

[Jim Underwood]

As I did a bit of research trying to find an aftermarket replacement motor for my Jet 1642, I realized a couple of things.

One: the motors and VFD, are essentially the same as the PMs, just have different shafts and mounting plates. I don't know if it's possible to swap one for the other, but it looks like it'd be a pain, regardless.
Two: An aftermarket motor is going to be very difficult, if not impossible, to find. If you find something, please let me know.
Three: These motors have a history of getting bent shafts for one reason or another. I've been blamed by several folks for overtightening my belts. I'm not sure it's my fault, since I haven't used this machine very heavily.

Regardless, if it's not your bearings, then it's probably the shaft, and you'll have to replace the motor.

Eventually when mine totally gives up, I'll buy the motor.

If yours is still under warranty, DON'T WAIT to get it fixed like I did, and have to pay the bucks myself.

[Sid Matheny]

Take it to a local motor repair shop and save a bunch of money! Anytime I have a motor to go that is what I always do.