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BumpI have nothing to contribute but would like to know the answers to this rather important question. Mike
Gun metal is 10% tin, while 660 Bronze is about 7%. I doubt it makes much difference at all in model making. I've been quite happy using 660.
Known as bearing bronze, C93200 has excellent machining properties, good hardness, as well as strength and wear resistance with excellent antifriction qualities. SAE 660 bronze has a long life span, making it an ideal alloy for bushing and bearing applications. C932 brings a machinability rating of 70, giving it a vast number of potential applications. Copper Alloy 932 is not subject to dezincification.
Stick with the 660 bronze. Easy to work with. Definitely don't want to use any of the aluminum bronzes. Like Ampco 18 or such. Difficult to work with unless you need it.Work with the 660 frequently.
A key part of the question is whether the bearing bronze is okay for the boiler parts?
And isn't "dezincificaiton" the thing that people worry about with Boilers & steam?
Yes, but you need a certain amount of zinc content to get into trouble and your bearing bronze does not have enough of it.