Reconditioning a Relmac lathe

[irving2008]

If you want to get it hot you will need to lag it :D

Silly question... Are you faffing about casting because you don't have another lathe to cut the new bushing on? Do you need help?

Robin,

Well I wouldnt call it 'faffing' as such... there is an element of learning a new skill here too :) but you are correct in that currently I dont have access to another (working) lathe.

Even if I did, I don't entirely see how to create a bronze bushing as the spindle is offset in the casting. It would need to be turned down from a solid 1.75" round and bored out to 1.25" approximately 3/16" offcentre. But then the castings would need to be line bored to ensure they are concentric and parallel with the bed as the advantage of a poured bearing is that it isn't dependent on the alignment of the external casting as long as the spindle is in line. Thats not true of the bronze bearing.

Irving...

[Robin Hewitt]

It would need to be turned down from a solid 1.75" round and bored out to 1.25" approximately 3/16" offcentre. But then the castings would need to be line bored to ensure they are concentric and parallel with the bed

It seems very odd that they would have bored the headstock off centre. If the tail stock does not offset, have you checked for signs of jiggery pokery? It may have a history which can be undone, making the replacement bush easier, but you'd probably want a shoulder to take the end thrust.

[irving2008]

Robin,

If you look at the picture below you can see how much of an offset it is... the bearing itself is quite thick and is side spilt. The main reason it is thicker on the split side is because the spindle is keyed to retain the bullgear and when you extract the spindle the key has to pass through the bearing. To give a strong positive drive they wanted to use a fairly substantial key and that meant they needed the bearing to be thick enough to allow a slot for the key to pass through (you can see the slot to the left in the pic, just above the split in the bearing, out of focus tho). But to have that thickness all round would have made it difficult to pinch down without straining the casting, so they offset it in the casting. Thats easy to do with a poured bearing and meant the casting didnt need to be too accurate. I suspect they had a jig that clamped to the bed with a long mandrel with a built-in key and this allowed them to pour both bearings at once and in alignment..