Do I need a hole in sintered bronze bearings

Hi All,

Sorry if i'm posting this when it's already discussed on other threads.
I have read answers to similar posts but want to be sure about my specific application.

I have an old Zyto lathe I am restoring which needs new headstock bearings.
The headstock has oil feed holes at the top to lubricate the bearings which I guess I could fit drip feeders to if needed.
The old bearings have holes lined up with the oil feeds to get the oil to the shaft surface.

I have found Oilite "sintered" bronze bearings the exact imperial size I need.
From what I have read I should not drill sintered bearings as it could seal the small holes existing by the design of sintered bearings.

So my questions …...

Will the oilite sintered bearings be OK for the load of an old small lathe headstock ?

If I don't drill a hole and feed oil through the holes in the top, will the bearings soak and distribute the oil enough to give the required lubrication ?

Many thanks in advance for your experienced advice

Thanks,

Jim

Having thought about this, the best thing to do is ask the manufacturers of the bush! You can consider a sintered bush as made from tiny balls of bronze brought together under heat and pressure which sticks them together, but leaves some passageways between the balls. You can see therefore that if you drill the bearing, you will squeeze metal into these passageways, and block them,. A lot depends on the rate that the bush will allow oil to pass right through its wall.. They are designed to hold the lubricant in the passageways, and are to a great extent, maintenance free, apart from the occasional oiling into the felt pad that usually surrounds the bush. As the bush warm up with use, it lets a bit more lube out of the passageways, and capillary action draws more oil out of the felt into the bush. if your bush will pass oil through itself at a sufficient rate, and slow drip lube is provided to the outside of the bush, with an oilway in the housing the full diameter of the bush, it should be fine but the manufacturers will KNOW all this stuff, and it would be sensible to check it out before you go to the trouble. Is there any wear on the spindle? if there is you may find you still have play, hope this helps.

phil

Edited By Phil Whitley on 13/11/2018 21:28:15

Thanks Phil for your very detailed reply.
Doh …. I was hoping for a simpler yes/no answer.
no disrespect meant

is it really that complicated ?

I thought it would maybe be a bit more simple in the way a sintered bearing would absorb and distribute the oil.
I'm very interested in the detail behind this but surprised at the complexity of your answer to my question.
Is it really this complex ?

Thanks very much again for your reply

Jim,

Let me try a simpler answer: Generally accepted 'best practice' with porous bearings is to to let the oil rise through the bearing by capilliary action ... so a little reservoir at the bottom of the bearing [*] is a much better solution than dripping oil into a through-hole at the top.

Presumably Zyto either didn't understand this, or didn't care. [edit: or the original bearings may be plain bronze]

The simplest 'fix' [if there is room] is to use two narrow bearings with a small space between them.

MichaelG.

.

[*] 

Edited By Michael Gilligan on 13/11/2018 22:44:37

I can't imagine that Oilite bushes would be suitable for use as lathe headstock bearings.

Martin.

Would a sintered bearing cope with the side loads generated by a lathe?

Bedtime reading: **LINK**

http://www.bowman.co.uk/bearings/oilite-bearings-self-lubricating-bearings

Maybe several nights-worth ...

MichaelG.

No, don't drill oil holes in sintered bearings. Oil dripped in from the top will spread throughout the honeycomb structure of the sintered particles.

Yes, sintered bronze bearing should be adequate for use in a small home-hobby lathe such as your Zyto.

Solid bronze bushings hand-scraped to finish may bear a bit more load and last a bit longer, but only a bit so not really worth agonizing over. Of course, solid bronze bushings are available from bearing suppliers in most of the same sizes sintered bushings come in, so it would be just as easy to replicate the original solid bronze bushings, which should have an oil hole drilled in the top as the original did.

Your choice.

Might be me misunderstanding again but I think the whole idea behind Oilite Bearings is that they are maintenance free. The matrix is vacuum filled with oil at the factory. In use, you don't feed oil into them, they are fitted to the equipment and run until they wear out. (Oilite can be refilled but I don't believe it's done much.)

Oilite suits many equipments, like electric fans, that have limited lives. The bearings only have to last for as long as the equipment is useful, which may not be long. Not having to pay a man to squirt oil into bearings is an important way of keeping costs down on small motors. And sealed bearings last longer than those contaminated by the clot in charge of maintenance!

I doubt fitting an Oilite bearing to a small lathe would be a disaster, but why bother when the original plain bearings are still available and oil can be dripped through them in time honoured fashion? Although plain bearings have largely been replaced by more modern types they still make sense on a lathe.

Dave

I think what SOD says is good sense. If the oilite bush is the easiest to get, and the bearing structure can withstand the side load, it should work.

OTOH, I can't see the harm in drilling the extra oil feed hole if you want to make sure there's always an adequate film between spindle and bush. You'll only compromise the capillary action through the interstices locally in the region immediately around the hole, and you'll more than compensate for that with the extra oil film and reservoir you'll create. Me, I'd suck it and see - and buy an extra spare bush just in case.

Edited By Mick B1 on 14/11/2018 16:32:54

I wouldn’t suck it and see. I would do as PW suggested. Probably look up the specs on t’internet first, but I would not be compromising the bearing unnecessarily, for no good reason.

I replaced a pair of sintered bearings on a water pump fan shaft. They leak oil all the time as they are fed from what should be a supply, by gravity feed, from the engine. I know they are working OK because of the dirty front of the engine and that the fan shaft has minimal play, while the water pump is not leaking past its seal. I hate to think how much oil would have been lost if I had drilled holes in the bearings! They have been there since the middle 80s.

I was intrigued to see from your patent link that the Germanic-sounding Herbert Kohn Staub was a British subject. Picador were major players in the early days of my interest in machines and it is a shame that they seem no longer to function.

I just don't think an Oilite bush will work as expected in this application.

Lathe spindle bearings of the plain type are usually of hydrodynamic design, which means that the spindle rides on an oil film induced & maintained by its rotation. This would need fairly sizeable unbroken bearing surface areas to contain & support it and is something porous bushes don't have.

Martin.

The only time I can remember adding oil to oil item bearings is when they had lost oil due to incorrect storage. Then before fitting the bearing was left submerged in suitable oil for 24 hours. I have never used any additional external oiling after fitting. Perhaps for this installation a bronze bush such as a Glacier du would be better, then additional oil loss system could be used for lubrication. Also a du would be have a higher load rating.

Thanks very much for the replies.

Based on all that has been said, I think I would prefer not to use Oilite bearings but after an extensive search I cannot find plain bronze bushes in the size I need.

The size needed is 1” ID, 1-1/8” OD AND 1-1/4” long.

Any ideas where I might find these ?

Glacier DU is ptfe. Chap in our club has oilite axle bearings on his loco with feed holes through the shell. It has lasted for many years, although I agree this probably isn't that many hours. ML7 countershaft bearings were oilite I think, and they last for ever.

SKF (skf.com) do solid bronze bearings I think. Look under bushings. They do your (imperial) diameters but you'll have to cut down a 1 1/2" long one down to 1 1/4".

McMaster Carr in the USA have 1" ID 1 1/8" OD 1 1/2" long oillites at the link below. Could be shortened easily to 1 1/4" and will carry a hell of a load for a hell of a long time for very little money. A couple of these in an envelope may not be a very big package at all, so postage to UK might not be outrageous. Just a thought.

https://www.mcmaster.com/6391k649

That's if they will ship to individuals in the UK, Jeff. They won't to Canada (citing security concerns for all this bog-standard stuff which was invented - more that a century ago - in Europe). At least at my last count that was the situation which was admittedly a few years ago now. Haven't tried recently.

They do ship to companies in Canada (or something that looks like one presumably) which may be a way for individuals to circumvent it.

you can get oilites at Bearing Boys in uk

**LINK**

as Jeff says, shortening them is easy and you don't need to worry about closing the pores if you're just cutting the end off. the issue with dfrilling/machining refers to what will eventually be the bearing surface. Unless the tools are very sharp, the surface pores get smeared over and stop being porous. If you are drilling a hole radially who cares.

Another complication s that the bearings seems to be split longways and adjusted with a pinch bolt (at least according to the pictures on lathes.co.uk)

If you have another lathe available, why not just get some cored bronze and machine to size?