I've always taken the "just about able to hold it" temperature to be about 60C, based on something I read years ago, but I must admit that I have never actually tested my personal temperature calibration!

My concern is that I'm not that certain that the motor is fully rated for slow-speed operation, but as it is the one that Denford fitted together with their original speed control board, I guess it's OK. Have to say that it does seem like a fairly big motor for only 1/2HP but it's presumably the one that came with the lathe and that dates back to the 70s. It originally came with a cassette recorder for toolpath storage!

Thanks for the comment - I'll check the label and just keep an eye/hand on the motor when using it to make sure it doesn't get stupidly hot.