Fitting thin-walled Oilite bearings

I have had this problem (bushes compressing and losing clearance on press fitting) with bronze bushes, where I could not ream to fit afterwards. I turned the O/D down until they were a push fit in the housing, then fitted them using Loctite 238 if I remember right. Result was a perfect fit and the bushes have remained firmly in place for many years despite arduous use. Not sure if Loctite will secure Oilite, but Henkel have an excellent advice service. Andrew

Thank you Andrew(s)

The ball bearing sounded like a good idea but I had wondered where people were getting them from? I had no idea that you could purchase large single balls - but prompted by your suggestion I searched online - and up popped Simply Bearings with a hardened chrome steel ball for a few pounds.

7/8 inch Diameter Grade 100 Hardened 52100 Chrome Steel Ball Bearings Simply Bearings Ltd

So I will order one and see how we go - my Warco 2B is probably man enough but I don't want to stress it.

I've 're-bushed' quite a few things over time, either because of wear or to change the bore size. Loctite has been my favoured solution (rather than a press fit) but I was also really not sure about this approach on Oilite.

Thanks again everyone.

Regards,

IanT

I have secured Oilite bushes in the past with Loctite 638. This has usually been when the oilite bush has become loose in the bore during service and the machine is needed to be in use ASAP. Loctite will however close in the bore of a thin walled bush, so one needs to think about this.

I would imagine the bond would be be very good as the adhesive has an increased area of contact given the porous nature of the material. This will allow the Loctite to flow around the particles of the sintered material.

Regards

Gray,

Does this (use of loctite) not render the sintered material non porous and defeat the point of oilite bushes which I have always understood to be to retain oil in the pores and thereby provide continuous lubrication.? Some installations have oil cups for recharge (Myford clutchshaft for example) so sealing the outside of the bearing with loctite would seem not to be a great idea. (At least to me). My thinking assumes that the bush is in a clean state with no oil in the pores. If the bush is full of oil then who knows where the loctite ends up. I notice Graham says he has used it to retain loose bushes in the past and he knows a thing or two so maybe I'm off track. It would be interesting to know what does go on when mixing oilite bushes and loctite. As an aside, we used oilite bushes on our rotating anode X-Ray generators for many years and the bushes were cleaned and filled with oil under a vacuum. The bush sat in a small puddle of the correct oil and the vacuum chamber was pumped down which removed all the air from the bush replacing it with oil by capilliary action resulting in a fully lubricated bush.

regards Martin

Ball sizing is effective but its not quite as simple as it seems, especially with Olite bushes.

Oversimplifying you are basically expanding the bush to increase the interference fit in its carrier.

The fact that the bore comes out the right size is, physically speaking, an incidental benefit. So, ideally you need to do the maths to ensure all the stresses et al work out properly or, better, follow established practice where someone has already done the maths and verified that everything works in practice.

One place where ball sizing is really handy is when you can't install the bush with enough interference fit for security e.g when you have to cold install in something that really needs to be heated to get the interference. Pushing the ball through gives you that extra hold. It also give you a bit more room on tolerances. In our sort of practice not vastly different to using loctite with the advantage that the bore comes out dead on and the surface smoothed out.

With Oilite ball sizing is essentially an alternative to using a mandrel to control compression on installation so you work to the same tolerances and sizes if you don't have any specific ball sizing data. Basically a mandrel increases the interference fit by reducing compression on installation whilst the ball gets the same effect by expansion afterwards. The important thing is not to apply so much force that the internal pore structure is significantly disturbed.

The compression on normal installation alters the pore structure but the bush is designed and made in such a way that the distortion produces the right structure so the oil moves as it should.

Oilite fitted without compression using loctite doesn't seem to work very well. The couple of times I tried that the Oilite bushes wore rapidly. Having a lifetime supply of "that size", which simply happened to be dead right for the repair job n question, I simply treated the replacements like simple bronze and oiled them on a sensible schedule which worked out fine.

It occurs to me that using loctite to repair fit bushes that have come loose for some reason ought to work better than using it on new bushes. The bushes will originally have compressed when fitted so the correct pore structure will have been established. Can't see any serious loctite migration into the bush happening and any outside sealing effect will surely not be vastly dissimilar to the effects of the interference fit from the housing wall.

Clive

Edited By Clive Foster on 01/10/2022 11:55:14

My example of using Loctite to retain an Oilite bush was to show it does work. The amount of Loctite used would probably have only penetrated a few microns. Given most bushes have a 1 to1.5 mm wall thickness I do not think this is going to seriously affect oil retention.

When a machine is stood idle because there are no spares, or the lead time for a replacement is days away. Then it is a case of needs must, or you have to turn patients away. The bush was later replaced with a new one, but the original was extremely difficult to remove. Not wanting to use a drift on such delicate machinery I made a dedicated extraction tool. This work being carried out at the next scheduled service.

Regards

Gray,