Pulsing circut

Hi
I am in the process of constructing a rotary table for use with my
welding robot. I have a large (36" dia) cnc rotary table that I had
purchased on ebay. It has a 140v DC servo mounted on it for the
movement. I have purchased a AMC brush type dc servo amp that has a
step (com, +10v) and direction (com, +10v) pins. My idea was to
program a plc with the required foot switch and two limit switches (one
for each position of the table) to control the servo amp and communicate
with the robot controller. I chose to power the servo though the servo
amp because when power is removed from the step pin, the motor will stop
instantly, but the problem is the speed at which the table turns. The
limit switches do not accurately activate at the same place each time.
So my next idea is to install another set of limit switches approx. 1
1/2" before the position limit switch and to send a pulsing circuit to
the servo amp to effectively slowing down the motor so that the position
limit switch can more accurately sensed. Does this make sense to
anyone? So my question is, does anyone know how to build such a
circuit, possibly using a pot to adjust the frequency of a +10v pulse.
Thanks

David Paulson