Adding more pulleys to increase the speed of my lathe?

[Thomas Lawson]

I have a very old Milford lathe with three speeds from a leather link pulley belt.  It seems fine for turning bowls, but I think it may be a bit slow for fine spindle work such as turning pens.

I don’t think changing the existing pulley sizes would make enough difference, but what if I added a shaft with a pulley set in between?

Is this a crazy idea?

I realise it would decrease the torque on the motor, and may stress the bearings…

[Bill21]

What sort of speed are you hoping to achieve? If you’re only turning small stuff at high speed the torque may not be a problem. The bearings may be an issue though. What type are they and are they easily changed?

As a point of interest I had to do the opposite on a metal work lathe as the slowest speed was a bit  too fast for my liking when thread cutting. In my case I made and fitted a much smaller motor pulley. It’s been on there well over 10 years now.

[Duncan A]

It's a common arrangement on 12 speed drills, with the intermediate pulleys as a jockey wheel.
Duncan

[Bill21]

It’s the same on my milling machine, but it was designed that way.
Thomas’s concern about the bearings is a valid point. They may not be rated to run at the speed he wants?

Edit: Looking on the Lathes.co.uk site the author is not sure what type of bearings are in the head. He assumes they are ball races?

http://www.lathes.co.uk/milford/

I’m not so sure though as there appear to be lubrication points at each end of the headstock?

Maybe time to take the spindle out and have a look.

[Twisted Trees]

I would say smaller pully on the motor is the best way forward as long as the bearings are rated for higher speed. Extra pully needs an extra shaft and bearings to go with it.

[Bill21]

Other way round.

https://www.aimsindustrial.com.au/blog/pulley-speed-ratio#:~:text=The%20bigger%20your%20driven%20pulley,less%20torque%20it%20will%20produce.


This may be useful as well.

https://www.engineeringtoolbox.com/pulley-diameters-speeds-d_1620.html

[Twisted Trees]

Other way round.

Ooops yeah bigger to smaller = more speed, sorry

[Bill21]

We all have senior moments. It keeps things interesting at times.