I made a brew and sat down on my stool with a packet of digestive biscuits and give it some thought. I was turning the original pulley around in my hand I noticed that the pulley had very small v shapes running all around the inside. I examined the pulley on the headstock and thats the same. I took the belt off and examined it the belt is less than a 1/4" wide but it has V shapes on the inside of the belt.
So I assumed they were there for a reason so I went to plan B.
I refitted the belt with a temporary small pulley. I then machined the original small pulley that was attached to the original motor to fit the new motors 5/8" driveshaft. I was not sure there would be enough meat on the pulley it was tight but we got there.
I fitted it tensioned the belt crossed my fingers and started the lathe. I chucked up a 5" long piece of 2" round aluminum bar stock I faced it off no issues I turned it around and faced the other end no issues.
I then took a light long pass along the length of the bar with no issues I slowly increased the depth of cut on each pass. I can take at least four times the depth of cut I was taking before with no issues
I could probably go deeper if I wanted to push it.
I repeated the exercise with a 30mm piece of bright steel with the same result.
YIPEE



I am a happy bunny I can now crack on with my projects. Except I have to go into work next week. There is all ways a downside.
