Just a little addendum.......
I've been ploughing........ Roughing a
lot of metal from a couple of flywheel castings.
Started at 5" diameter, with a 1" wide rim, alloy castings.......
Mini Lathe Motor. Again.......Around 200rpm.
The speed control, set around 1/3 of it's travel. Which is not the best position for motor cooling......
Mini Lathe Motor. Again.......Not a ha'p'orth of bother! Just ploughed on. Half a mill per pass, o/d. 30thou per pass, facing.
Motor felt slightly aired. Same with the extractor fan outlet. No alarming smells from the windings.

The result.....
Mini Lathe Motor. Again.......I reckon we've cracked it!

Thanks once again Lads, for all your help and encouragement. I couldn't have done it, without you all out there.

David D