Brass vs phos bronze

[portbury]

Hi Folks,

A newbie here, asking for some basic advice .

Just starting to make some phosphor bronze clack valves to replace the existing brass ones (club I belong to isn't keen on brass for boiler fittings) and I wanted to check that the metal I have is actually phos bronze? I'm somewhat colour blind (not to mention inexperienced!) and am pretty sure that the bar I'm using was sold to me as phos bronze, but it seems to machines like brass. I believe it could be leaded phos bronze, but not sure. I've taken a photo of various bits of bar I have in stock, the top piece is phosphor bronze, the bottom piece is brass and the middle piece is the one I'm not sure about...

www.atomic-album.com/showPic.php/45823/P1070071 (Large).JPG[/img]
Any advice gratefully received,

cheers

Rich

[kneedeepinswarf]

Hello Rich,
I think the metal you have is continuously cast leaded gunmetal. I bought some of this material from RS Components, so I can be sure of its identity, and it has the same "ringed" surface finish. This material should be fine for use on boilers, but due to the lead content, I am not sure if it can be siver soldered successfully.

[baggo]

Hi Rich,

I agree that it's cast gunmetal. I have several pieces which also came from RS and the spiral pattern on the outside of the bar seems a feature of the stuff.

I've used it to fabricate cylinders and made large boiler bushes from it. It silver solders ok but doesn't seem to like too much heat. I initially used Silverflo 24 to solder it but the surface of the gunmetal seems to 'bubble up' at the high temperature needed for this. This could well be due to the lead content. I've had no problems using Silverflo 40 and Easyflo.

John

[russell]

I recently bought some phosphor bronze rod from Blackgates and it has the same spiral pattern so Rich,s could equally be PB. Not that it makes much difference for boiler fittings.
Russell.

[portbury]

Many thanks folks,

sounds like it's definitely not brass and is suitable for making boiler fittings, so all systems go

Cheers

Rich

[baggo]

May 22, 2008 18:38:06 GMT russell said:

I recently bought some phosphor bronze rod from Blackgates and it has the same spiral pattern

That's blown my theory then ;D Obviously the marks are down to the method of manufacture.