[smclean1969]

It varies quite a bit from one machine to another. If you have your mill stalling out, there could be a few different issues. The most likely one is you're taking too big of a cut based on what the machine is rated for. The easy solution is to take a smaller cut.

You could also using cutting oil or some other type of approved lubricant to maintain the material at a cooler temperature which prevents chips from being welded to the part it was just cut from. It will also extend the life of your end mills.

Your end mills may be dull. If they're used heavily, then you probably should be replacing them every other year.

A little more complicated may be if the belts inside the mill are worn out so they don't have as much friction to turn the spindle.