Nema 42 Motor Size Question

[15mgtar]

I have bought the wrong motor size which are nema 42 size with 19mm shaft. Can you guys tell me which rack and pinion size to buy? I will be running mach3 in metric.

[KenC]

Ouch!
No worries, IMHO, you can still use Mod. 1 gear & rack, 24 teeth will be too small but 30teeth is big enough to cater 19mm shaft.
You need to mod the laser profile parts as well, motor mounting plates & carrier plates... Just a few that I cna think of.

[15mgtar]

Thank you Ken, where do you buy your rack from?

[KenC]

Deitech in Hong Kong. they are cheap but with some quality issue, which is still well worth my money.

[bradm]

15mgtar, you have several things to check/solve before proceeding with those motors.
- Shaft size / pinion size; if you'll be happy with the final gear ratio, what the torque will be.
- Redesign of the motor plates, also clearances of the motor positions, changes in the springs.
- Drivers capable of running those motors; power (voltage/amperage) to run those drivers, speeds of the motors, etc.

Bigger doesn't always work out -> think installing a tractor motor in a motorcycle.

You might find it easier and less expensive in the long run to return or E-Bay those motors and get another set.

[KenC]

I second Brad's advise. Unless you are competent with the necessary design alteration on your own.

[Richards]

Size 42 motors may be difficult to drive if you use Gecko stepper drivers. Big motors may require expensive electronics. Big motors often run much slower than smaller motors.

I agree with Brad and Ken. Rather than redesigning the machine, it would be easier to sell the motors and get some size 34 motors that better match the design.

[MetalHead]

Ditto on the sell and rebuy of Nema 34 motors.

[Gerald D]

Why a stepper motor should not be too big . . . .

[15mgtar]

I already have the motors and the drivers . the drivers runs on 110-220vac. Selling them would be a greater lost, I'm very low on money so I just have to stick with them.
I really don't know about shaft's size/pinion size (19mm/30???maybe 34 minimal?) and final gear ration so if you guys would kindly guide me through.

[KenC]

I recon not selling them will be a ever bigger lost.
Sell them & start over again.