# Gunmetal or Brass



## vcutajar (Dec 24, 2011)

I need to machine a part in gunmetal (yellow brass). The instructions specifically say "gunmetal and not brass". The raw material came in a kit. How can I distinguish between gunmetal and brass?

Thanks


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## Tin Falcon (Dec 24, 2011)

tell us what the part is you may want to use bronze instead of brass. Unless you are running an engine a lot under load substitution of material is not a problem. 



> How can I distinguish between gunmetal and brass?


there may be some color differences but short of chemical testing or a spectral analysis not conclusive. 

for general parts brass is just fine 360 is the free machining grade.  for bearings and cylinders bronze is preferred
IIRC brass is an alloy of copper and zinc bronze copper and tin gun metal copper with tin and zinc.
tin .


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## bezalel2000 (Dec 24, 2011)

Hi Vin

Brass/Bronze covers a huge range of alloys - litterally hundreds of different types and compositions.

in really general terms Gunmetal (LG2) is a Red Brass at about 85% copper with equal amounts of Tin, Zinc and lead to make up 100%.

Yellow Brass usually refers to Copper/Zinc only alloy with a Copper content lower than 70% ( at higher levels of copper the brass takes on a reddish hue) when not otherwise specified it is likely to be either 1/3 Zinc & remainder copper or 60/40 - Cu/Zn

Bez


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## vcutajar (Dec 24, 2011)

The part that needs to be in gunmetal is the rocker arm bush. If this engine ever runs, I do not intend running it for long periods. Just for fun. As Tin suggested I am going to use the hexagonal section that came with the kit, whether it is gunmetal or brass, and see how it goes.


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## Noggin (Mar 22, 2012)

vcutajar  said:
			
		

> The part that needs to be in gunmetal is the rocker arm bush. If this engine ever runs, I do not intend running it for long periods. Just for fun. As Tin suggested I am going to use the hexagonal section that came with the kit, whether it is gunmetal or brass, and see how it goes.



Gunmetal is not generally available in anything but rounds. LG2 or SAE660 should be fine for the job.


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