What 'decent' Milling machine?

[Jess]

Look for denfordata on google to get the mill details as well as lots of info from people who have probably converted them to Mach 3 and / or modern drivers etc.

Yes, everything should posted somewhere on Denford's forums; might need some digging though!

Caution however, if it's a dc motor thyristor drive it is NOT isolated from the mains and you will need an isolating circuit to link the drive to your BoB.

Given the simplicity of the circuit needed for this (in the common PWM output case, it's one opto-isolator, two resistors and a capacitor), I'd probably avoid a breakout board that has a non-isolated 0-10V spindle output on the basis that it's been overly cost-reduced.