Bronze questions

[razzle]

Ii have two questions I am hoping someone can answer.
1. What is the US equivalent to 'Gunmetal'? What alloy designation?
2. What bronze alloy is appropriate to use for boiler bushings?
A lot of the model engineer Youtubers just call it gunmetal or bronze and never tell you what the alloy is. When i look at bronze alloys at US metal suppliers the list gets completely overwhelming. I know that some bronze alloys are difficult to machine and/or impossible to silver solder. So i want to know which alloys are the correct ones to use.
Thank you.

 

[jkimberln]

According to Google, gunmetal is called red brass in the USA. For boiler bushings in copper boilers I use SAE 660 or 93200 (same thing) which is easy to get at McMaster-Carr, Speedy metals, and Online Metals. For bushings in steel boilers, I use steel bushings.

 

[kwoodhands]

From what I gather gun metal is 88% copper, 10% tin & 2% zinc
The color is a dark gray . I have used phosphor bronze or aluminum bronze for bearings, bushings and twice for gears.
mike

 

[DJoksch]

I have a bunch of Oilite bronze and was thinking it might work as a steam cylinder sleeve.

 

[Nerd1000]

They're probably referring to LG2 bronze, composition 5% tin 5% zinc 5% lead and the remainder copper. C932000 should be an acceptable substitute.

 

[abby]

Gunmetal , so called because it was developed for cannon barrels before cast iron , is as already stated red brass in the US and has a composition of 85:5:5:5 Cu b:Sn:Zn. It is good for any steam fittings including boiler bushing and cylinders. Brass should not be used as the zinc is gradually depleted by the steam leaving very weakened fittings.
Dan.

 

[razzle]

I had seen the 'red brass' designation for US, but that is as vague as 'gunmetal'. I did read of a designation for 'admirality brass' which is denoted as 'bronze G' but I only found that listed on one supplier and the cost was too rich for my blood. The sae93200 gives me what I was looking for. I just got Stan Bray's book 'Making simple model steam engines' so I have some projects in mind and am trying to pull together a list of supplies. Getting the right bronze alloy was my biggest hang up. Thank you.

 

[Charles Lamont]

660 is primarily a bearing bronze. It is probably fine for boiler bushings, but I would prefer to use something with a lower lead content. My own choice would be phosphor bronze. Gunmetal is more commonly used for castings, and while it can be obtained in continuously cast bar, it does not seem to be widely stocked. UK designations are LG2 & LG4 for leaded gunmetals, and PB1, PB2 & PB102 for phosphor bronze.

 

[comstock-friend]

I have a bunch of Oilite bronze and was thinking it might work as a steam cylinder sleeve.

Oilite (sintered bronze) is intentionally porous to hold oil for lubrication. Don't use where it needs to be steam tight.