I have a Denford Starmill, converted by previous owner to Mach3.

The spindle is belt-driven from the motor hidden in the column, and can be adjusted upto around 3000rpm.

The last time I used it it popped the circuit breaker a couple of times before settling down okay, whenever the motor span up - something of a concern! That, coupled with the pretty low rpm (I'd like to use the machine for PCB drilling/milling, and would prefer to get up to 24k rpm) has lead me to think of the chinese water cooled spindles.

The existing spindle is held in place with two 80mm dia (ext) bearings, with belt drive to the motor. The spindle tooling is the old BT45 style, for which I have a ER32 collet holder. All that I can live without.

One thought I had was to remove the spindle and bearings, disconnect the motor, remove the bearings and bore out the circular rib (somewhat less than 80mm dia) that holds the bearings apart, then fit a 80mm chinese spindle motor in situ, directly driven (no belt) with some form of bracketry. But, boring the rib might be a challenge! (depending on the weight/shape I might get it in a 4-jaw on my ML7).

Another thought was a narrower bore spindle motor that would slide in with the rib in place, and turn a top and bottom sleeve to hold it in place (essentially replacing the old spindle bearings).

Is this a sensible idea?, or plain crazy? The mill at this time is good for steel (which I do very little of), but very slow for ali and next to useless for PCB - I've not got the space to realistically host two machines, so I need to make this a practical single machine.

Any advice, gratefully received. (or any pointers to a cheap [<£1k] alternative)

Mike