irving2008: When I contacted Astrosyn I was adviced for the best speed and torque to run the steppers at 30-40volts not exceeding 1amp per phase.

I know that running at this kind of voltage is going to make alot of heat.

The heatsink is not a computer / cpu heatsink

The heatsink it's self is 85x90x4mm if you include the cooling fin's it's 85x90x24mm so the fins are 20mm, I do also have a 80mm 12volt fan bolted to the heatsink.

Kip: I am using unipolor as that is all my driver boards support.