[gicos]

NC Cams, your inbox is full. Hopefully you can chime in here.

I'm working on an oddball project. Take a 4 pole induction motor, press the shaft out of the rotor, hog out the rotor ID for a larger hollow shaft (without getting into the squirrel cage), press the rotor back onto a new shaft. I've done the homework electrically and it will work with a small loss in power. The motor is for driving a portable lathe which needs a large pass through hole for the work being done.

The shaft is connected directly to a chuck in a spindle-less setup. The shaft is 1/4" thick 4140 tubing, internally tapered at the front to accept ER50 collets. The rear may run a fan or a pulley, I haven't yet decided. Motor will turn up to 7K RPM for short runs from a VFD.

The original plan was to install these bearings in custom face and rear plates:

50x80x16,MR6010C-ZZ/C3 #5 EP2 EMQ,Metric, Electric Motor Quality (EMQ) Bearings

but NC Cams' posts have made me reconsider this, especially in the thermal expansion department. The 50mm ID is about the practical limit price-wise as large ID bearings go. The next size up doubles in cost, the next triples, etc. Initial plan was a press fit against steps on the shaft and a press fit of the races in the end plates, with either shims or bolts in the plates for preload.

I think it would be wise at this point to ask those more in the know how you'd do it before I end up smoking $250 in bearings.

[Al_The_Man]

Unfortunately NC Cams passed away a few years ago.
Al.

[gicos]

I'm very sad to hear that, Al. Not because of my little project, but because the world is now lessened.