Fitting thin-walled Oilite bearings

Finally got back to re-building the headstock of my Atlas MF mill.

Started as a bit of a clean and check, ended with the machine completely in pieces, stripped down and re-painted. Decided it was worth changing all the bearings for new ones, including the Timkens. Came to the headstock pulley (which includes the backgear). There are two new 1"OD x 7/8th ID Oilite bearings to refit, a 1/2" and a 1". Checked that they fitted over the shaft OK, then used the same M8 threaded rod (with steel formers) to pull the first 1/2" bearing in place. The shaft won't fit now. Partially inserted the 1" and got the same result. Removed both bearings and neither now fit. Clearly I've compressed the 1/16th walls by this method. Two new bearings have just arrived in the post.

So, what to do?

Thinking of trying to lap the (aluminium) pulley to make the bearing insertion easier but maybe I'm missing something. Any suggestions welcomed.

Regards,

IanT

Edited By IanT on 29/09/2022 09:36:58

IanT

Oilite bearings compress slightly on installation. Its inherent to the nature of the beast. As, for practical purposes, they cannot be reamed to size you have to find the specified bore size for your particular bearings and take out the bore to size first.

Specified size varies for bearings of the same size from different makers so its often not safe to simply change old for new. I have the impression that modern oilites compress a bit more than old style ones.

Last ones I fitted, about 3 weeks back, needed almost no nip to come down to size. Frankly I'd have liked a thou or so more for better retention. But it will work.

Clive

Good morning, Ian,

I fear that I can't give you the link to the web-site of the manufacturers of Oilite bearings but you should be able to find it easily.

That web-site used to have a section on fitting the bushes. If I remember correctly, they advocated the use of a mandrel of the same diameter (or plus a running clearance? ) as the shaft that was eventually to run in them. This ensures that the bushes contract to the right extent.

I hope that helps.

Best regards,

Swarf, Mostly!

Hi Ian,

When I have installed Oilite bearings they do close up a little when pressed in, just enough to be a running fit. Are the 1" hole reamed to 1"? I assume you have read their Best Machining Practice or Engineering Assist?

Thor

Edited By Thor 🇳🇴 on 29/09/2022 10:06:17

Were the original bushes Oilite or plain bronze? Oilites are made with oversized bores to allow fo slightr compression when fitted. Your machine might have housings sized for plain bushes.It is possible, but not ideal, to machine oilites. can you take a bit off the ODs?

Were the original bearings oilite ? Could it have been solid bronze or steel backed abronze lined ? Reaming them will spoil them, is there a burr caused by crushing the edge as they were pulled/pusged in ? Check data for the bore size of the hole your fitting them to. A new chainsaw file eg 3/16" may help to clean up and not costly ! Noel.

Ian,

Did you pull the bearing into place with a fitted bar in the bearing? Would this have prevented any constriction of the internal dimension and left it at the desired diameter, upon removal of the plug? Maybe need a fraction larger?

While reaming is not permitted, a sharp boring cutter can be used - as long as it cuts rather than ‘smears’ the surface of the bearing. Smearing prevents lubrication while cutting does not.

Yes you should use a sized mandrel inside the bush when fitting. And yes you can ream the Oilite bushing after installation. This is according to Oilite's own literature.

To find a PDF of the Oilite fitting instructions saying this, do a google search for "Oilite bushing fitting instructions". About the third listing down on the search results will a site address something like Https//: bearing.co.il .> oilite PDF. Click on it and you will download the Oilite brochure. For some reason I am unable to copy and paste a link so just follow the said procedure to find it.

I have never bothered with the sized arbor. I just ream the bushes to size afterwards with an adjustable hand reamer and they have worked perfectly. Inspection with a magnifying glass will confirm there is none of the alleged "smearing" of the sintered bronze particles. Oilite does specify to use a sharp reamer though. You can also bore the bushes with a sharp HSS toolbit.

OIlite bushes I have reamed like this have been running for years without problems.

Ok, thanks everyone.

Some good food for thought there. When I eventually get around to it, I'll report back on my progress (or not) - balancing my time between getting outside repairs and inside (insulation) work done on house before cold weather really sets in. Main workshop gets very cold and I'm not going to be (fan) heating it this Winter, so visits will be very brief.

Regards,

IanT

My experience is the same as Hopper's I use a sharp reamer and looking at the surface with a x 10 eyeglass shows no sign of the alleged "smearing".

I have done this on several UK made single and three phase motors. I did the first one 15 years ago and it is still going strong, with no hint of "shake" from the shaft.

I suspect it is one of the old wives tales, similar to the "Tool MUST be on dead centre when turning a taper", G H Thomas nailed this fable and showed that errors caused by not being on dead centre were totally insignificant.

Andrew.

Hopper, Andrew

When it comes to reaming Oilite say :-

"Oilite bearings may be reamed provided a dead- sharp cutting tool is used. However, reaming does destroy porosity more than single point tooling."

I think it doubtful that typical Model Engineer/ Home Workshop Guy tooling will be good enough for a reamed Oilite bearing to work perfectly well over its full specified performance range and lifetime.

Which is a whole different thing to "works well enough for me in my home workshop".

Generally the things we do are very much at the light duty end of the bearing performance spectrum and actual running lifetime but a small fraction of the specified life under industrial conditions. So odds are that a significant amount of pore smearing is unlikely to make much difference to folk like us. Especially if the shaft and bearing are lubricated before installation.

I seem to recall being told that if pore smearing is sufficient to be visible using normal inspection optics the self oiling properties will have been almost completely destroyed. Sufficient sub-surface damage to affect performance can easily be done with no reasonably visible effects. I gather the engineering of and operational modes of these things is somewhat more complex than simple description implies.

Think I'd be looking for a brand new carbide spiral flute reamer if I had to ream one and be confident it would still work well.

Most of my adjustable hand reamers are essentially new and nicely sharp but I'd not trust their ability on that job. I agree that its highly likely that they would do the job well enough to produce an at least adequately functional bearing but its not the sort of chance I like to take. Especially no given the temporal investment in disassembly to get at the offending bearing and re-assembly afterwards.

Clive

Edited By Clive Foster on 29/09/2022 12:13:19

IanT,

my Oilite catalog from ~1975 lists the following :

AA-1008-9 .876" ID x 1.003" OD x 1/2" (noted that as stock is sold will become obsolete)

AA-1008-6 .876" ID x 1.003" OD x 1"

AA-1009-3 .877" ID x 1.003" OD x 1" (no listing for 1/2" wide)

What many people do not know is, back in the good, old days there were Oilite Bushings available with various OD/ID size ranges. I am refering to actual Oilite Corp (Amplex division of Chrysler). As an example for the common 1" ID x 1-1/4" OD there are (were) :

1.001" ID x 1.252" OD

1.002" ID x 1.252" OD

1.003" ID x 1.253" OD

1.005" ID x 1.2525" OD

for most of the Oilite materials the tolerances for all the above values were +.000/-.001". Oilite Corp had 7 different materials to choose from.

Hi

Hi-jacking the thread little bit!

Would a 1mm wall thickness work for a camshaft bearing made from an oilite bush?

There is an oil supply from the engine.

The ID is 12mm and the OD is 14mm, the OD was machined down.

I thought the sintering might break down.

Cheers Michael.

Is Oilite necessary if there's a steady oil feed from the engine?

Well thank you again - I've been up a ladder all afternoon, probably not the best thing for me to be doing but basically a simple job if you can reach it and I'm afraid these things cost silly money around here if you try to get outside help.

So, my current thinking is that the old bearings look like Oiltite and were probably made by them too. The new ones are from Simply and most likely from the Far East. They are a close fit to the shaft, which is slightly worn on the section where the bearing runs but not on the first part that the bearings need to slide over when being re-installed. I probably have a 1" reamer (haven't checked yet) but doubt it will be "razor sharp".

So I'm going to make a fitted 7/8th mandrel to pull them in, with a separate 1" top-hat that can be removed, so that I can then pull the mandrel out after the first operation. I'm also going to try and make the bearings an easier fit in the pulley. Since my ability to turn/bore to very fine limits is clearly not as good as some folk here, I'll most likely lap the 7/8th mandrel to a very close fit, which will also give it a very fine surface finish. Same with the pulley. I think (for me) it's probably easier to work on the bits that surround the bearings than the bearings themselves. I suspect that if I can get the shaft to actually pass through the pulley (with bearing fitted) when re-building - that the bearing will run fine on the shaft once it's in (due to wear) and anyway it can be run-in.

So don't hold your breath - lot's of other stuff to do first - but thank you for your feedback

Regards,

IanT

Don't "make the bearing an easier fit in the pulley". This is begging for the bushing to spin within its hole and will end up trashing the pulley it is pressed into. Leave the hole alone. You need that interference fit there to hold the bushing in place. Do not mess with it.

If you make a sized mandrel, read the material from OIlite mentioned above. You need to make the mandrel bigger than the shaft you want the bushing to fit. You need to add at least a thou for oil clearance, plus about half a thou for "spring back" when you remove the mandrel. So 1.5 thou bigger than the spindle would be about right.

And if it ends up too tight after all that, don't be afraid to use a hand reamer on it. It works. Don't let perfectionism or fear of the unknown stop the job getting done, or even worse, causing bad work practices such as enlarging the hole the bushing presses into.

Not sure what you are planning re "lapping" the mandrel to size. Whatever you do, don't put any abrasive near that oilite bushing. You will never get it out again. Turning the mandrel to almost size and finishing the last thou or so in the lathe with emery cloth should work ok. Then clean it off before fitting it into the bushing. .

Regards,

IanT

Oilite bearings I have purchased from Amazon are variable in quality. Those I have purchased from Simply Bearings, (the usual disclaimer), have all been of excellent quality.

All Oilite bushes need to be inserted into a standard H7 Fit bore. When this is done the bearing collapses to the correct running fit on the shaft. If the bore does not conform to the H7 tolerances then you will have problems.

Oilite stick material is still available I have been told. This can with good tooling be machined to size. It is however very hard on HSS which may mean continued sharpening. Carbide tooling tends to rip the small bits of sintered material out of the structure of the material.

If you can get hold of a ball bearing of the nominal size this can be pressed through the bearing to size the hole. You will however need a very good press to do this.

I hope these notes help,

Regards

Gray,

Thanks Grey - yes, they are from Simply Bearings.

I generally use SB or Bearing Boys, both have been very good in terms of price, quality and delivery.

Don't have a suitable ball bearing (or large press) but it has made me think about chamfering/rounding the leading edge of the pull-in mandrel more carefully. Keep coming back to the pulley bore being correctly sized (as Goldilocks would want - not too big and not too small but just right)

Regards,

IanT

Expanding on Graham's suggestion of using a ball, that's the method I used to size the new Oilite bushes I fitted to the pulley of my Tom Senior mill. They were 1.1/8" bore and were too small after being pressed in.

It didn't take an inordinate force to press the ball through and was well within the capability of my 1/2" drill press. I used a steel rod in the chuck with a 60 centre drilled end to locate on the ball. It's not difficult to compress the sintered structure. There was a certain amount of 'spring back" of the bush after the ball was forced through so I heated the ball for a few minutes in boiling water and that enlarged it to give the running clearance I wanted. The result was a perfectly round highly polished bore that was still porous and exactly the size I wanted. I think this method is less risky than reaming.