Turning down a servo motor shaft. Anything to look out for?

I’ve got new Chinese ac servos on the way as discussed in another post. The large 180mm frame y axis motor has a 35mm shaft and I’ll need to reduce it to 24mm to fit the pinion gear for the reduction gearbox, as per the original yaskawa.
Being an AC motor I’m assuming I can simply remove the rotor shaft assembly, chuck it up between centres and turn it down.
When removing the encoder can I just mark it’s location on the shaft and reinstall the same way? Will that be sufficient?

Basically what I’m asking is, what’s going to bite me on this?

That’ll be fun
Will be interesting indicating it true with such a short shaft.

there are tupper returnings for shaft size reduction

is it a relal need or can you get the servo to a side and make some Timingbelt in between

taking the servo apart is always a risk of cracking the bearings

The body is square but I don’t think I’d trust it to be perfectly true to the shaft. It’ll be fine, slowly slowly during setup and lots of checking with dial indicators will get it done.

I’m just glad you guys gave me the heads up on permanent magnet motors. That would have made for a bad day.

unless the motor is *very* old, i bet it has a rare earth magnet rotor which survives just fine being pulled out of the stator. the tricky part is not to scratch the rotor coating. i have replaced bearings on a few servos, although smaller ones - 1HP and lower. i also turned a straight shaft to a taper on a 400W mitsubishi servo.

i'd also think about the possibility of fixing the motor somehow to the lathe bed and turning the shaft under it own power. the one i modified was free-machining steel, very easy to turn. haven't tried that, but should work, imho

Yeah, I'd considdered removing the encoder and having a look, there must be something there for the encoder to key onto and I'd like to bet that there's a centre drilled in whatever's back there. That might be a quick and simple answer. Shaft between centres, hold the body still (just so it's not flogging around) and use a drive dog.
Motors haven't turned up yet, I had a quick look at the original Yaskawa (which I suspect the new chinese motors are a copy of) but I'm reluctant to mess with them.