steppers without flats on shafts

[davidma]

I picked up a couple nema34 compumotor 83-93MO motors from a surplus shop for a good price. i looked up the specs, plenty of torque for my little micro mill.

BUT, they have no flats or keyways on the shafts. how are you supposed couple anything to the shaft?

I guessI could heat up a bushing and do a press fit on it. but then how would i ever get that bushing off if i needed to replace it?

[Jason Marsha]

sdp-si has split hub coupling that clamp onto the shaft, this won't mar the shaft like a set screw.

Jason

[widgitmaster]

If you are using a coupling with one or more setscrews, simply assemble everything as it will be used, tighten the setscrews so they make a mark on the shaft, then disassemble. Then use the edge of a flat file exactly over the marks left by the setscrews, two or three strokes of the file should give you a small flat for each screw!

Eric

[Tim Tanner]

Originally Posted by widgitmaster If you are using a coupling with one or more setscrews, simply assemble everything as it will be used, tighten the setscrews so they make a mark on the shaft, then disassemble. Then use the edge of a flat file exactly over the marks left by the setscrews, two or three strokes of the file should give you a small flat for each screw! Eric

Hi Eric,

This will only work if the motor does not have a hardened shaft, very often motors do.

Regards,

Tim.

[mxtras]

If it's hard then use a die grinder - just spread a small amount of grease around the shaft/housing interface and cover any openings to prevent crap from getting into the bearings and motor.

The method described is what I have done in the past - use the set screws to mark the shaft and either file or grind small flats. I have heard using a pointed dimple on the shaft with a pointed set screw is better than a regular set screw on a flat but I just use a flat for simplicity.

Scott

[davidma]

useful info, thanks.

now that I know there is a workable solution for the flatless shafts, i can go back to the surplus store and pick up an even bigger compumotor for use on the Z axis!

these compumotors have some sortof connector that i have never seen before. i should post a pic, and maybe get some help identifying the style of connector so i could put mating connectors on a board that i want to build.

[Jason Marsha]

A picture of the connector and the motor would be nice. Does the store have a website?

Jason

[phantomcow2]

Helical beam couplings will work too, they clamp on the shaft rather than use a set screw.

[davidma]

Originally Posted by Jason Marsha A picture of the connector and the motor would be nice. Does the store have a website? Jason

here are a few pics showing the motor and mystery connector.

the store is vetco surplus http://www.vetcosurplus.com/

i don't think theye show motors in their on-line inventory. the compumotors i got there i think were a 1-time deal. i think people sell their old junk to them, they disassemble them and sell out the useful parts (power supplies, motors, etc)

[Adobe Machine]

mxtras method is the best if there is no keyway machined into the motor shaft. I know that you save a buck or two by not specifying the correct keyway when you order the servo or stepper, but the hassel it causes later would dictate that you should order with keyways...1/4 " shafts or smaller will not support a keyway, so the instructions listed by Scott are very appropriate. I have always used two set screws in this situation, 120 degrees apart, and if the pully flange is thick enough,use two sets ( one on top of the other) to lock, instead of "lock tight".Always mark that you used 2 set screws some place obvious..I can not tell you how many shafts that have been torn up because they loosened the top set, not knowing there was another underneath.

Adobe (old as dirt)