Need Help!- New NEMA 42 steppers for BOSS mills

[CNCISME]

I have a retrofit Logitrol kit I bought from a man who originally bought it for this BOSS 5 mill that I also bought from him. The kit has NEMA 34 motors and the half inch diameter shafts are about half as long as the original 5/8 stepper motor shafts.

I know there are negatives to NEMA 42 compared to NEMA 34 motors concerng torque and rpm's but I can not use the NEMA 34 steppers due to shaft issues.

I have Gecko 201 drives ..... what would be my best choice for a new NEMA 42 stepper. I plan to sell the NEMA 34 motors

can anyone help me out?

...I have a 1:1 drive pulley ratio on this machine.

[HawkJET]

Originally Posted by CNCISME what would be my best choice for a new NEMA 42 stepper.

From what I can tell, the NEMA 42 motors that Bridgeport uses were most likely built to Bridgeport specs by Sigma and Superior Electric. They have a longer-than-standard output shaft and a nonstandard diameter. I have a Boss 3 and am also interested in replacement motors.

My machine is running with the original steppers with Compumotor drivers and Mach3. If you have the original motors, use them to get going.

It seems that normal NEMA 34 motors have a 1/2" shaft and NEMA 42 motors have 3/4" shafts. Both are still too short.

The original steppers are a very old design and are not optimized for micro-stepping. I am looking for replacement motors so I can gain the advantages of micro-stepping. Smoothness at low feedrates and better resolution should improve surface finish (especially when interpolating).

My plan is to use NEMA 34 motors with a ROUND 1/2" shaft (no flats) and make a 5/8" shaft extension.

[CNCISME]

Thanks HawkJET

Check out my "Adapting NEMA 34 steppers to original pulleys" thread if you haven't already... unfortunately my motors had flat shafts but Mactec has a good solution for me. How will you lock the adapters to the shafts ?

[HawkJET]

Originally Posted by CNCISME How will you lock the adapters to the shafts?

Since the pulley is about an inch from the face of the motor, I'll make the adapter 3/4" dia. between the pulley and motor face. I'll step it down to 5/8" for the pulley to fit. The 3/4" diameter will give me extra beef to allow for a decent 'squeeze' for a shrink fit.

The adapter bore will be about .001 interference fit, and will be heated to expand it to slide onto the motor shaft. When it cools, it will be locked in place.