Having dismantled the wiring on my Boxford C lathe, I discovered that it was 'shocking'. No earthing and some wires not rated for mains voltage, so a fire risk as well as unsafe.. (I should mention that my lathe is heavily modified by the previous owner.)

So my question: can I expect the motor on the lathe, which is I believe, the original Brook Crompton motor, to pass modern insulation tests, and to what voltage?

The reason I ask us that it measures 60Mohms when only tested to 250V which is less than the 160Mohms required to pass (the motor works OK,btw)

Is it possible that it just needs a good clean or is this a common issue?

Thanks for any advice,

Kevin.

The supply is RCD protected so I'm not concerned from that point of view. I guess I want to know if I should expect it to pass or not. If it should pass then I will need to strip it down and find out what the problem is and maybe even have to source a replacement.

I already have a lot to do to rewire and reassemble this lathe.I was considering changing the motor drive but was hoping to do that at a later date.

Kevin.

Thanks for the comments. I double checked – you are correct that the pass limit should be 1Mohms, though guidance is to investigate for <2Mohms. I was mislead by my new (to me ) digital tester which allows you to set the pass impedance for different standards – should know better So the motor may be OK, though I still expect open circuit to case, so it may be full of swarf as you say – hadnt thought about cast iron swarf..

I measured just the motor. The motor is the far side of a pwm controller – 1980's tech by the look of the PCB – it has RCA power transistors ! If I PAT tested the lathe in total it would definately have failed. I started out at 250V to be cautious, but yes it should be tested at 1kV.

As a cautionary tale, the mains wiring was awful. 3A flex twin core, no earth, no gromets through the stand walls, to the latching on off switch – to be replaced with a zero volt release switch and emergency stop switch. From there, the live and neutral to the controller, but also a switched live to a changeover relay for reversing the motor. The later fed on the multiway alarm cable used for the speed potentiometer, probably rated 50V ! Terminals were taped over with masking tape, and where they were touching there are char marks on the tape. Also dry solder joints in several places resulting in heating. Amazing it didnt burn the previous owner's house down. I guess it didnt run long enough to get going.

The lathe has many mechanical modifications as well, including having the spindle modified to accept 2c rivett collets – sadly the nose end is missing, so my first turning job will be to make a new one. There is also a non standard gearbox for the leadscrew, and various small gadgets I havent entirely worked out the purpose of.

Having said that it comes with lots of gear, and it seems to be in fairly good nick. I think its had the bed re-ground, as the apron sits low so that the handwheel has rather excessive slack on the rack.

Sounds like its worth stripping the motor down anyway, so I may do that.

Thanks,

Kevin.