Ali Bronze v Phos Bronze

Does anyone know if aluminium bronze is suitable for lathe headstock bushes ?
I am refurbishing a 1950s Winfield lathe (don't ask why - I just AM)
and have acquired a spare headstock with nicely made new bushes in ali bronze. I have no idea whether this is the right sort of metal, as I would have used PB1 and have some of it waiting. Should I throw the bushes away and start afresh, or will it be OK to use them?
If you ask me whether my spindle is hardened, then I would say not. Did they really harden lathe spindles back in the good old days, and if so how (induction hardening, case hardening or what) ? I am not convinced they used to bother, maybe they just used a slightly better steel grade. Unfortunately the only hardness tester I have is a file, which is not so good at telling you if its a 'bit' hard !
Grateful for some guidance.
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wrote:

In my opinion, both Aluminium Bronze & Phospher Bronze may be too hard to run an unhardened steel shaft in. If the spindle is hardened then Phosper Bronze would be fine, but Aluminium Bronze is probably the hardest and most corrosion resistance Bronze and wouldn't be a first choice in this application. If the spindle is 'soft' then Leaded Bronze may be a better choice. It's a bit more conformable and is more tolerant of imperfect fits and poorer lubrication.
Others may disagree or have better suggestions.
Peter
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wrote:

There was an article in ME by the late Dave Lammas on refurbishing a Winfield headstock about 10 15 years ago. He used leaded phospour bronze IIRC. I'll see if I can look it up since the article was very sensible.
Charles
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On Sat, 21 Jan 2006 09:55:52 +0000, Charles Ping

ME Vol 167 No 3911. Dec 20th 1992 My scanner is playing up but I'm happy to send you a photocopy next week if you like.
Thanks
Charles'
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Charles, that article sounds useful if you can get your scanner to work.
I thought the idea was that you had to make sure the two metals in a bearing were different hardness otherwise one would pick up on another. That would mean you use a soft metal on a hard shaft, and vice versa. I remember years ago being told you must never run hard on hard, for example you must never use chromed piston rings in a chromed cylinder bore. So if you had a soft steel shaft you would want hard bearings - does this make any sense ?
Also if you have third party abrasive in there (which is not the intention) then the hard metal is worn at the expense of the soft - in fact the soft metal laps the hard metal. This means its tricky to decide whether a spindle is hard or not from the wear on it.
It all seems 'orribly complicated. Is there a book on bearings, maybe its time for some homework ?
Steve
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Finally found some info on the web at australwright.com.au
They have a product data sheet on copper based bearing materials which compares quite a range and suggests (to me) that phosphor bronze and ali bronze are pretty much similar, but that leaded bronze offers better conformability. Both have very high hardness and wear resistance. Conformability is presumably to do with bedding in and whether the spindle shapes itself to the bearing or the bearing to the spindle...now which one do I want given the spindle is hardly perfect ? Tricky.
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wrote:

Steve, I'm not an expert on tribology so my opinions would need verifying. What you said is true but it's also all relative, how hard is hard and how soft is soft. Certainly the surfaces need to be a different hardness to minimise wear, but you also need to consider the anti-friction properties. Ideally their should always be a film of lubrication between the two surfaces, but where there isnt ( i.e. a typical hydrodynamic-ish drip fed lathe spindle after its been at rest) then the bearing material needs to have some inherent lubricity. Aluminium Bronze has poor anti-friction properties and could lead to galling and seizure when run with a softer shaft/spindle.
There is a lot more information here: http://www.copper.org/applications/industrial/bronze_bearing.html and here: http://www.machinedesign.com/BDE/mechanical/bdemech6/bdemech6_9.html
The other consideration although somewhat obvious I know, is that when choosing your material which component would be easier to replace, the spindle or the bearing, and then make sure that the one that is more difficult to replace is the one that is designed to wear the least.
However having said that, it doesn't always seem to happen in practice. I'm replacing the leadscew on my ML7 because of wear on the bearing surfaces at both ends (the screw threads were badly worn too) and the leadscrew seems to have worn more than the bronze Oilite bearings that it runs in. FWIW I'm making the new bearings for this out of LB4 leaded bronze.
Peter
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Peter,
Maybe the leadscrew bearings have got some machining dust in them. This would explain why the leadscrew is more worn than the bearings, when hard particles are present then the soft metal laps the hard metal.
Thanks for your thoughts, and the links. I will at least learn something this weekend.
Steve
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Try the copper development association's guide to copper alloy bearings.
http://www.cda.org.uk/megab2/costeff/tn45/index.htm -- Dave Baker
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Thanks Dave,
That is a chunky reference, shoukd keep me quiet for a while !
Anyone know a good source of leaded bronze ? That is looking favourite from all that has gone before.
Steve
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Steve wrote:

Steve, Leeds Bronze are probably the biggest UK stockholder but I don't know if you can buy direct or whether you need to find out who distributes for them.
http://www.leedsbronze.co.uk /
Regards Peter
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Which bronze to use is a constant issue in race engine work. Valve guides, little end conrod bushes, cam bearings etc. It would be nice if there were simple answers but usually there aren't. However what this often tells you is that the choice is not as critical as you might suppose because most types of bronze will work passably well in most situations.
Although tribology is complex and often the softer surface acts as a lap and wears out the harder surface faster there seems to be a general rule with bronzes that the softer they are the quicker they wear out. I've used ali bronze for valve guides and it's a superb material although a right bugger to machine. It last many times longer in extreme applications than softer bronzes like manganese bronze which is really just a high tensile brass. Colsibro came along some time ago and briefly became "the" thing to use for guides but others swear by phosphor bronze and others still by silicon bronze. Frankly most of it is bullshit and marketing to get you to buy their particular choice of product.
What the OE manufacturers use is often more determined by price and ease of machining than suitability for the task. I remember chatting to an engineer at Cosworth some years ago about valve guides for a particular application where they used cast iron for the road engines and bronze for the race ones. The bronze ones wore out so fast that people started paying a premium for road heads with iron guides because they lasted more than a few races in race use. He admitted that the choice of bronze was soft, cheap and easy to machine rather than long lasting and that they could have made a better choice.
If you already have finished bearings to hand then I'd suggest slap them in and they'll probably be fine whatever they are made out of. You can agonize for ever about a better choice of material but you'll probably never reach a definite conclusion or know whether you were right after the event. Bronzes generally don't wear out steel shafts if lubrication is adequate so I can't see this turning into a major problem and I equally can't see ali bronze wearing itself out fast whatever the application. -- Dave Baker
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Thanks Dave, what you say makes a lot of sense. I feel reassured and will use the Ali bronze bearings. Not only would it be a shame to not use them given the work that went into making them, but it is also the easiest option and will hurry things up.
You raise an interesting question re valve guides. I am shortly to do an engine rebuild on my 650 Norton (its rather on the smoky side!). It will probably need valve guides. Last time I had the head done was donkeys years ago and I remember then having a choice of bronze or iron guides. I went for the bronze and subsequently heard they tend not to last very long. I think I opted for them because it seemed better to use a metal with a closer expansion ratio to aluminium so there is less risk of them coming loose in the head. As you said, they probably go for a grade that is easy to turn given the tolerances required. Maybe I'll have a go at making my own this time around - see if I can achieve the required precision in AliBronze.
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