For those that don't want to read the full article that Brad linked to, here is the pertinent data:
Attachment 377218
So as you can see, most steppers set at the most common (1/8) setting only have around 20% of their published torque. Be aware that that is when stopped. (Holding Torque) Assume 30% less than that when moving at normal cutting speeds, even less when rapid moves are executed.
Remember that those "honkin beast" 370 ozin nema23 motors on 3:1 belt drives with a 25 tooth pinion gear will develop no more than 15 pounds of force when moving. Less when hot. If on linear rails which have 3-5 lbs of frictional force, is it any wonder why I recommend against NEMA23 for commercial applications? Any wonder why machines fail an hour or two into a cut file? Any wonder why a rotary axis wont hold against off center cutting operations? Any wonder why rotary axes fail most often when doing a rotary raster that everyone loves so much?
I don't.
And remember that the 370 ozin motors I refer to are about the largest used on small machines, most are substantially less.