Make a blank cap with centre thread and screw in a bolt?

A threaded cap with a bolt through the middle is a great idea, wish I had thought of that. But this is one of the revolving centres I dismantled and unfortunately it does not have a thread inside the end, the end plug is just pushed in and held with a rubber O ring. The bearings inside the body were a radial needle roller and a ball thrust bearing.

Nobody has offered any suggestions yet as to how to remove the bearing

Roy

The design of live centres differs widely, that one may only be dismantled by destroying the bearing. There will also be a thrust bearing behind the needle roller.

You may have to bore a steel plate or ring that will support the rotating end from the MT side and press the centre out.

Another way would be to make a replica of the front end, drill and fit a grease nipple and force grease through the bearings without further dismantling.

Edited By old mart on 14/03/2021 15:24:04

Edited By old mart on 14/03/2021 15:27:17

Edited By old mart on 14/03/2021 15:30:32

Try the grease method, take out the 6mm bolt and replace it with a grease nipple and gently pump grease through. The grease will work its way through all the bearings until it emerges at the back.

That bearing is an open needle roller bearing with no inner race. **LINK** The hardened shaft runs straight on the rollers, as a slightly loose running fit. So the shaft does not need pressing out of the bearing as you would do with a ball bearing with an inner race that is a press fit.

So there must be something else holding it all together. Possibly a pin through the outer housing that locates in a groove in the shaft or something similar. There will be a radial needle roller in behind that visible bearing to take axial load but that too will not stop the main part from coming off in the opposite direction.

Some of those centres with the tapered outer body have a concealed join somewhere along that taper and the body is pressed together at the factory. Each half goes either side of an integral flange on the shaft that bears on the radial roller thrust bearing. Not really designed for dismantling once together. I think they machine the taper after the two halves of the body have been pressed together, so it is really hard to see the join. Or the join may be where the taper meets the parallel section of the outer body. Careful inspection with a glass might reveal?

So be wary of trying to press it apart with bolts or even grease pressure. You may distort the flange on the inner shaft that the radial thrust bearing runs on. Heat from a torch may expand the end half of the body enough to come away from the inner half? Kind of operating in the dark though if you cant see that join on the taper and be certain.

As the bearing is open onto the central shaft, with no seal, standing the unit up vertically and pouring oil down into the bearing space might be enough to free it up. Would only need a couple of drops. You don't want to wash the factory grease out. Or melt a little grease in a tin an pour a small amount in instead of oil.

You could then pack the cavity with a bit of grease, leaving some air space, and screw the centre in with some gasket sealer on the thread to stop the grease coming out.

Edited By Hopper on 16/03/2021 02:28:42

Edited By Hopper on 16/03/2021 02:37:45

Yes that might do it without needing disassembly. It's construction will be an enduring mystery.

I wouldn't be surprised if your live centre turned out not to have any seals fitted, there is not much room for swarf to enter through the rear.

Stick a thin feeler gauge up the gap and feel if there is rubber or metal in there?

If there is no o-ring or seal, maybe the grease is gravitating downwards while the centre is stored in the usual manner, nose upward. Maybe keep it nose downward between use and drain the grease back inwards again?

I imagine if you put a grease nipple on a threaded plug and fill it chockers with grease, it will ooze out all the more. Plus not good for the bearing to run in 100 per cent grease with no air space. Tends to overheat the bearing as it tries to pump the grease around in there, which then destroys the grease which then lets the bearing wear prematurely. Usually aim at 50/50 grease and air in a bearing cavity. Or even less. And needle rollers dont really like grease. They are happier with a thin oil. But maybe in this low stress low rpm application grease is ok if it is a thin grease like white lithium Optimol etc?