Cheers Jonathan!

Hmm might go for a small DC motor instead to get a bit more torque and run the shaft. The only reason why I thought of steppers for the driver is because I thought I might use a stepper controller, which normally covers 4 steppers. I could then interface with the controller using a microcontroller based circuit via an LCD interface, although I'm not sure how easy that is. I think most controllers are plugged into to a PC via an RS232 / 485 port, so I'd need a circuit which handles that, or it might be easier to build a stepper controller using LMD18245 chips and integrate everything into a single circuit.

Based on that formula for the torque, the value comes out rather small:

F = 3kg * 9.8mm^2/s = 29.4N
L = 1.25mm = 0.00125m
e = 0.3

T = (29.4N * 0.00125m * 0.3) / (6.28) = 0.00176Nm = 0.176Ncm

which is way below even the smallest Nema14 motors, so it's not bad news. Unless of course I've messed it up somewhere.

Regards,
dsc.