suppliers of gunmetal

[Garry Coles]

Hi everyone
Can anyone please tell me who can supply cast gunmetal in various sizes in the UK, also, why do we use this metal for some of the fittings on locos and not brass or phos bronze.
Thanks

[gwrfan]

Hi Garry,

You will find that Blackgates Engineering, Bradford, West Yorkshire, have a good supply of cast gunmetal, in round and square sizes from half inch to 3 inch. Try this link to their website:

www.blackgates.co.uk/body_materials.html

Gunmetal is usually used in castings such as hornblocks and cylinder blocks, etc, whereas phosphor bronze is usually used for steam fittings, boiler bushes and so on. Brass isn't really suitable for steam fittings as it will eventually rot! The more learned amongst us will no doubt enlighten us with the science behind this - I hope, LOL!

Geoff

[the_viffer]

This is not exactly right but it might do as a first approximation.

Brass is an alloy of copper and zinc. In some alloys there are small bits of copper next to small bits of zinc. Stick it in water with some ions floating around and you have got a battery. Result a small electric current and the zinc turning from solid metal into soluble zinc ions. The term is dezincification. As gwrfan says this means that the brass has rotted and it will loose lots of strength.

Some grade of brass have the zinc and copper more intimately mixed and the battery effect doesn't happen. That means no loose of zinc. The trouble is that you can't see by looking at it which grade of brass you've got. So it is better to use a different metal.

You can use phos bronze for boiler fittings. It comes in 2 kinds. One is yellowy and cast. It turns up a treat. I have a commercial boiler with bushes made of it. I was a bit alarmed about the lead content but both the boiler maker and the material supplier envisaged no problem in brazing up.

Drawn phos bronze is evil. It is the coppery coloured stuff that grabs your drill and breaks your tap. It is fine for strength purposes but as it is nasty to work it is not a good choice.

Gunmetal is half brass half bronze. It is copper with some zinc and some tin. Often got some lead in it as well. The zinc is alloyed in a way that it doesn't dissolve. It is a bit easier to machine than many bronzes. You might hope that it'd be cheaper than bronze as zinc is cheaper than tin. Still mighty pricey.

BTW the price of copper is currently very high. Expect suppilers to try and raise prices.

Chap I knew reckoned that dogs weeing against lamp posts ought to be case hardening them.

[gwrfan]

Thanks T-W,

I knew someone would elighten us (me!!). Useful info, which I've copied to my own Documents File for future reference.

Geoff

[the_viffer]

Well take the typos out before you save it!

As I say it is not exactly correct.

The exactly correct answer is not far off this but harder to follow.

Alpha brass with less than 35% zinc is generally resistant to dezincification. This is the stuff you can cold work.

Cheapo brass with a higher zinc content so called alpha-beta brass will dezincify.

I'd check with the supplier before using brass in any kind of demanding environment. And get the answer in writing

[gwrfan]

Thanks again T-V,

But I have already saved it. Not worried about the typos, and sorry about calling you names (T-W!!). You should have heard the names I called my PC a little while ago, when the on/off switch jammed inside! Had to take everything apart, side panel off, and front panel off, to see the switch, which had snapped at the weakest (ie the 'springing bit) point!

I just had to have it up and running to get back to MECH, haha. But there's no front cover on it now, just a tiny plunger type switch. Least it works!

Geoff

[Garry Coles]

Thanks to all for your info, Blackgates are now sending me a catalogue.
I now have a choice of suppliers (Reeves, MCM, GLR and Blackgates) to help me choose all I need to build my next 5 year project !!!!! 3 1/2 g William. Its taken me weeks to work my way through the plans and list all the metals I wiil be needing.
Garry

[waggy]

Gary,
R.S.Components do gun metal and other "stuff" via mail order at reasonable prices. You have to create an account at rswww.com
I ordered some bearings about 12-00 on a Monday, by 10-00 Tuesday I had them. Prices are reasonable and you don't have to drive miles to collect anything.

Regards,

Dave.

[the_viffer]

College Engineering Supplies in the Black (Pudding) Country would also be amongst my usual suspects for this stuff

[spurley]

Have a look at Macc Model Engineer's Supplies. Phone for a quote, 01625 433938, very reasonable. I am merely a satisfied customer and from Northern Ireland too!

Cheers

Brian