Phosphor Bronze vs Bearing Bronze

[Ramon Wilson]

Hello Kim, bit late in replying but you might find this useful http://www.modelenginemaker.com/index.php/topic,6744.msg138122.html#msg138122

It is a reply I gave some time back and then repeated - guess it might be worth doing it again.

As a basic guide I would plump for 'yellow' cast bronze for any bearings with unhardened steel shafts, 'gunmetal' for major components. The pink coloured drawn PB is lovely stuff to machine save for one op - drilling/reaming. It work hardens easily and will grip a drill tight beyond all expectation. A way round this is to grind the drill off centre to enlarge the hole. If reaming bore the hole to minimal reaming size and use lots of coolant - it gets hot extremely quickly. It's good for bushes in boilers and bearings too but usually with hardened shafts though I do use it on the untreated EN24T big ends in my IC engines. On soft shafts it can, though not necessarily will, pick up. If it does then it becomes near impossible to remove without damage.

The one thing to bear in mind on all bronzes is the tools need to be razor sharp at all times - anything less then the material tends to get 'pushed' with resultant poor surface finish.

Hope that helps some - sorry I cant find the original post - it is there somewhere

Regards  - Ramon

Edit - grinding the drill off centre on drawn PB only works if the hole is drilled in one. Step drilling is usually the only alternative until a boring bar can be used but every drill needs to be freshly sharpened for best performance with less 'stressful' results.

[Stuart]

Bronze in it forms is copper tin mix and brass is copper zinc  hence the problem with boilers.

the real rub is all the fittings you but are all brass  but your bushes must be bronze ha they would be a pain to replace bu

Boiler fittings can be , but are better in bronze esp. for loco use you don't want a fitting to let go while driving think of the proximity of certain body parts for us gents , sorry YL's

Edit for me being dyslexic

[Kim]

Stuart, Jo, Florian, Ramon,
Thank you all for your responses here.  I really appreciate it!

Based on this, it seems that the C932 "Bearing Bronze" should be an OK choice for me to make as a suitable material for use as boiler bushes and cylinders.  If I've misinterpreted any of your excellent advice, please do let me know!

Thank you very much!
Kim

[jadge]

Yes, but you need a certain amount of zinc content to get into trouble and your bearing bronze does not have enough of it.

Correct, generally more than 15% zinc can be troublesome. Dezincification occurs in the presence of oxygen and moisture so, in theory, steam should be fine. In practise, because of the low zinc content, steam and water should be fine in contact with what we in the UK call gunmetal.

Andrew