Modifying stepper motor shafts

I have resurrected the cnc conversion of my x1 mill and want to turn down the end of some nema 23 stepper motor shafts from 8mm to 6mm and thread it for the handwheel - double ended motors you see.

I had in mind just to chuck the other end of the shaft in the lathe and keep the motor casing still but will this kill the motor?

I've cut the keyways already.

Cheers

Andy

Hi Andy,
I can see no reason why this should cause a problem. I think it would be wise to support the motor casing and use a centre in the tailstock end. (Assuming it has a centre drilling.) I would keep the speed fairly slow. I was going to say below the motors maximum speed rating but a quick look at the specifications on ArcEuro's website does not give a maximum speed or stepping frequency. I would guess at below about 400 rpm. (This is just a guess. I have no information to base it on.) Make sure the wires are not shorted together as it will be acting as an alternator. They seem to use small stepper motors in this way in wind up torches.

Les.

Might be easier to keep the 8mm diameter and modify the handwheel, although that may not always be possible.

Doug

Or even make a new handwheel?

Russell.

.

Or, better yet ... use these

They are flexible in bending, but stiff in torsion.

MichaelG.

Thanks for all the good ideas guys, turned down no problem, tailstock support and motor lightly held in the fixed steady, 200rpm on the Boxford and a sharp hss tool.

I had thought of but discounted an adapter because the damn things are going to stick out an awfully long way anyway but John's advice to "modify the cheapest bit" makes excellent sense - I must try and remember that bit.

Andy

If you have the motor connected to a driver, even if the power is off it will be quite hard to turn the handwheel as the stepper charges capacitors in the driver. If you want manual control best unplug from the driver. Even better, use a manual pulse generator (MPG) to drive the stepper via Mach 3. I'm looking at "stepperature" which uses small steppers as encoders for just this.

John,

Thanks for your lead to stepperature

... I was unaware of it ... Looks very promising!!

MichaelG.

I have a stepper motor drive connected to the right hand end of the leadscrew of my Myford speed 10 lathe and use the enable input of the driver to disable the motor when it is not running.This arrangement has worked fine for some time but I do sometimes feel uneasy when I use my mandrel handle for screwcutting.

The turning of the mandrel handle rotates the stepper motor (incidently there is very little resistance caused by the motor  and I do worry about the back emf generated by the motor and the effect this might have on the well-being of the driver electronics. I presume that modern drivers have protection built in to prevent damage of this kind, but I still worry.

Doug

I wonder why the designer used a stepper motor for the basis of his design, he admits it can miss pulses at slow speed. Surely it would be better to use an optical encoder from an old computer mouse (or even an optical mouse)?

The only thing I can see the stepper being used for here is to provide a well engineered spindle with some detent action.

Ian P

Ian,

Yes, on further consideration I'm inclined to agree.

MichaelG.