Servo Question

I'm considering converting from steppers to servos (DC). After
looking at some specs it seems that continious stall torque is far
lower than peak torque. One motor I was looking at has a continious
stall torque of 3.313 lb-in, and peak torque is 300 lb-in! Why is
there such a huge difference? Can somebody give me a defenition of
each?


I know approximatly how much torque I want on the leadscrew, which
motor torque value do I use to figure out pulley ratios? Please help
me out. Thanks.

Mark