From Davo's and cmm's answers there seems to be a wide range of drill spindle speeds used (3k-30k rpm). So, just to add to that... 11,000 rpm would appear to be adequate.
I have been looking into converting a Wilson II 3D printer chassis into a CNC PCB etching machine, recently. In particular, what motor I needed to replace the extruder with.
A collegue pointed me to an interesting video, PCB making, PCB prototyping – UV solder mask STEP by STEP, produced by Wegstr (no affiliation whatsoever), and their machine uses a 11,000 rpm drill. From the specification page:
- Spindle - Brushless AC motor
- Diameter of spindle - 3.175 mm (0.000737 inch)
- Spindle speed - 11 000 rpm
Electronic overload protection for the spindle motor
Apparently DC motors suffer from carbon brush wear, so a combination of DC circuitry and brushless AC motor is used for "superior performance and durability".
The voltage and current of the spindle motor is unclear/unspecified, but the PSU, that comes with it, outputs 12 V 5 A.
However, the parts page lists the spindle motor separately, spindle 11000rpm, with the following specifications:
- 26V DC power supply
- 11000 rpm
- designed for tools with shank diameter 3.175 mm
- fastening tool with the setscrew
- in the rear spindle 4x M4 threaded hole for mounting on a substrate
- power consumption 25W
- brushless construction => no carbon brush wear => long life
- low noise
So, given the voltage and power consumption the current rating would seem to be ~1 A.