Homebrew PCBs

Derek,

These Precise spindles are some of the best for printed circuit 
drilling. I have a four spindle machine that uses Precise SC53 
spindles with the air collet. This machine uses a frequency converter 
for driving the spindles. Sometimes you can find these converters on 
the surplus market but they go for big bucks. I might have a 
schematic of the drive used in my machine if that will help you.

Some of the Excellon machines use a frequency converter made by PTI. 
I have also seen these on the used market for around $150. These 
converters are just a high voltage variable frequency three phase 
motor drive. Perhaps you could get some off-the-shelf industrial 
motor drive to do the job. 

BTW, you can put approximately 7 volts DC momentarily across any one 
of the three windings to stop the spindle in about five seconds. This 
is how the Excellon machines stopped the spindles. These spindles 
have excellent bearings and will spin forever after removing the 
drive voltage so some type of dynamic brake is used for rapid stop 
and tool change.

Tom