In choosing a good stepper motor I would start with the RepRap Wiki, the large choice available should help find a supplier closer to where you live. I think you can just divide the holding torque by 10 if you prefer Kg-cm over N-cm.
http://reprap.org/wiki/NEMA_17_Stepper_motor

If you have a good drive gear and stepper combination, the point of failure of the extruder is more likely going to be at the hot end, basically, I’m referring to any hot end; not just the E3D.

I only use PLA filament due to being able to print directly on to glass, so the J-Head MK5 hot end is perhaps the best choice for me. Personally, I wouldn’t buy an all metal hot end just for printing PLA.

Mark

Thanks for the information. Not yet having purchased steppers for my build, which would you suggest I go with? The cost difference is minimal and my goal is to minimize potential faults and attain the best possible print quality.

As for the comment about the hotend, have you had a negative experience with the e3d or do you mention it because it is far less tried and true than the ubiquitous j-head?

Emilio

The SY42STH47-1684B stepper motor is basically used as a benchmark for high level of performance, all the bowden extruder performance graphs I’ve produced in previous topics are based on this stepper motor.

Any stepper motor type that match or better the specification of the SY42STH47-1684B should provide a reliable direct drive 3d printer extruder. The SY42STH47-1684B can serve as a starting point when looking for a stepper motor for direct drive extruder.

It looks like you have already got a good set-up, I think if you get any problems at all, it’s likely going to be at the hot end side.

Mark

My application is a Mini Kossel using your extruder and a 1.75mm e3d hot end with .4mm orafice. Any input/suggestions are appreciated.