Jittering and jamming of stepper motors

[Belal Mohammad Hashmi <belal.hashmi-at-nu.edu.pk>]

I have installed emc with redhat 6.2 on a HP KAYAK PII 233 mhz machine to
control a bridgeport series I CNC. (got it up from scrap). I am using
stepper motors with freqmod.o. The motors do good, but at about 40ipm they
jam. what may be the problem. Period is set at 20, Prop gain=70. I,D gain=0
Velocity forward gain is 1.0 all other are 0. There are no following errors.
The steppers work fine through a signal generator upto 10k steps/sec. What
may be wrong?

Belal.