During the last few months I've noticed a slight intermediate noise coming from the mill which has been slowly getting worse. After a bit of troubleshooting, it seems to be coming from the electric motor. While it isn't sounding horribly bad yet, right now I'm in-between projects so it's a good time to perform some maintenance. Better to do this now before this problem becomes much worse and risk damage from spinning a bearing in the motor housing.
This mill uses a VFD to power the motor and provide variable speed control and because of that the motor is 3-phase. One of the many advantages of a 3-phase motor is that they are simple to disconnect (3 wires) and service as they don't have a centrifugal switch and capacitors like a single phase motor.
I've always wondered about a use for this mill's turret swivel feature, well here's one as it allows easy access to the motor that is installed at the back of the mill just by loosening a few bolts on the column and rotating the head assembly.
The motor's case is comprised of aluminum and therefore it's very light for it's size and I had no trouble removing this 1.5HP motor without any lift aids. For the record, the motor was made in 2008 which makes it 17 years old at the time of this article.
Pulling off the belt pulley. I've had this loosened-up before to straighten the drive belt so it came off easily.
On the other side of the motor is a cover which protects a plastic fan which was easily removed. Here I'm pulling the end bell off the fan side of the motor.
And there are the bearings. While both bearings would spin easily, one bearing produced a slight ticking sound while turning which is what I was hearing when the mill was running.
The housings for the bearings have no grease fittings so whatever lubrication that is inside the bearing is all it will ever have.
There's a wave washer in the bearing housing of the end bell of the motor. Don't lose it!
Pulling a bearing off. Obviously I'm replacing both bearings.
The replacement bearings: a 6205-ZZ and a 6203-ZZ. Both bearings were around $5 a piece.
Unfortunately I didn't take any pictures of pressing the new bearings back onto the motor shaft, but it's an easy job just make sure to press with a tube so the force is on the inner race of the bearing. For the rest of the bits, installation is the reverse of removal.
With the mill back together again happily the noise is now gone. It's amazing how annoying that slight noise was to me and I'm really glad I took care of this issue.