I ran my modified x2 mill at top speed (7,000 RPM) for 30 minutes to see how warm everything would get. The spindle was slightly warmed up, as was the cast iron head. The motor was very warm, but not hot. I could put my palm on it for 15 seconds without any discomfort.

I wonder how warm the motors become on other machines: Tormach, Industrial Hobbies, standard X3, X2, X1, treadmill motor conversions, and others.

Please post your results.