Hello all,

Firstly, sorry if I am not in the right section because there is a bunch of it

I am building/planning my first CNC that I aim to mill Aluminium with. It's a small desktop CNC but I try to make it sturdy.

But I have a hard time choosing stepper motors... I have established the size standard I will use : NEMA23 form factor.

I think, I have established the torque I need : about 2.8nM (430oz I think) -> Is it "correct" coupled with SFU1605 LeadScrew ?

I plan to use either a "OpenBuild Black Box" or a "CNC xPro V5" controller, so as I wish to use the internal stepper driver, I will limit myself to 4.2A of peak current.

What I really don't get about the spec sheet of motors is the relation between current peak and torque, it does not seem to be related like a traditional motor. I see 4.2A with 3nM of torque, sometime I see 6A with only 2nM of torque. Is the length of the motor influencing this ?

Maybe you can give me a general rule about stepper to help me choose ?

Thank a lot.