In the preceding volume in this series, we described a stepping motor automation package for XRD data acquisition, based on the Apple microcomputer with an interface card that produces the stepping motor pulses and counts X-ray pulses from the normal X-ray detector and amplifier. We are presently using the system to automate a General Electric XRD-5 diffractometer mechanism, by replacing the original synchronous motor with the stepping motor, and installing 10:1 reduction gear instead of the chain drive to drive the double worm gears. This gives 2500 steps of the motor per degree two theta. Motor pulses are counted by a small machine language routine which also handles accelerating the mechanism when slewing over long angular ranges.