I have a single speed drill press which I would like to operate
using a variable-speed foot pedal (rheostat).
It all depends on the type of motor your drill press has.
In order to use a rheostat type foot control, the motor needs to be
a universal ac/dc motor. Look on the motor name plate for the type of
motor. If it says ‘Universal AC/DC’ or ‘AC/DC Series’ the rheostat
Be aware that when using a rheostat & running at slow speeds the
motor won’t provide as much power as when running wide open or
without the rheostat.
A good source of foot rheostats for small motors is a store that
sells & repairs sewing machines. They use the foot control you are
probably interested in.