How to Identify Brass vs Bronze?
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    Default How to Identify Brass vs Bronze?

    I scrounged some brass or bronze bar mystery metal from a dumpster when they were clearing out a college machine shop 15 yrs ago. But I honestly don't know whether I have brass or bronze. Any way to tell them apart?

    I have a non-critical part I'd like to make out of bronze. Its a threaded flange. A hand crank will rotate a threaded steel shaft and the shafting thread will push/pull this threaded flange.

    The oxidation is a dark brown. When I cut into the bar it is a brassy color. just ever so slightly redder than 360 brass. So perhaps this is brass and not bronze. Oh well, if the flange is brass or bronze it won't really matter.

    But would like to make an educated guess on whether this stuff is brass or bronze. Any way I can be able to make an educated guess at this? Densitys look to be pretty close to each other.

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    When you turn bronze the chips are almost like dust.

    Bill

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    Found this. It says bronze drill chips are stringy. Whereas brass is flaky. I have turned and drilled a lot of 360 brass and I know how that behaves. How its grabby on a drill bit. But there are numerous alloys of each and they all behave differently.

    http://answers.yahoo.com/question/in...3230342AAEHfdg

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    My guess is that if you put the hydrochloric acid on it, it will go pink if it's brass.

    I'm basing that on the fact that over time this happens to brass fasteners in a marine environment.
    The chlorides in seawater fizz away the zinc and leave a spongy copper substrate which falls apart if you put it under any stress.

    Bronze has no zinc.

    I emphasise that this is just a hunch, but someone else here will know, or you could craft a Google search using 'de-zincification' 'brass' 'hydrochloric' and other terms in various combinations till you hit the jackpot.

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    Brass will generally be yellow in color where as bronze will be redder in color.

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    Quote Originally Posted by Troup View Post
    My guess is that if you put the hydrochloric acid on it, it will go pink if it's brass.

    I'm basing that on the fact that over time this happens to brass fasteners in a marine environment.
    The chlorides in seawater fizz away the zinc and leave a spongy copper substrate which falls apart if you put it under any stress.

    Bronze has no zinc.

    I emphasise that this is just a hunch, but someone else here will know, or you could craft a Google search using 'de-zincification' 'brass' 'hydrochloric' and other terms in various combinations till you hit the jackpot.
    yep, brass will look just like copper on the surface if washed in hydrochloric acid. what bronze does i don't know but i'm pretty sure there are some types that also include zinc?



    dave

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    Not to thread hijack, or anything, but this has raised my curiosity...

    My nephew has been using my garage toys to make a model steam powered engine for the experience of making it whilst doing an engineering course at the local college. We have made some parts out of, what I have been told, is "Aluminium bronze" (got it from the college), namely the cylinder and big end connector.

    Does anyone have any opinion as to whether the material is suitable, or whether we should remake the big end connector/bearing from phosphor bronze? (Again, college donated some material to the project).

    Thanks,
    Chris.

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    Quote Originally Posted by DazedConfused View Post
    is "Aluminium bronze" ... suitable?
    Aluminium bronze is a prince among bronzes, arguably exceeded (for most purposes) only by Nickel Aluminium bronze which is pretty much the king.

    They're outstandingly tough, hard wearing, damn strong, and pretty nice to machine.

    Also Alu Bronze is a particularly nice colour, nicer than PB :-)

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    Default Bronze vs Brass

    Quote Originally Posted by ZAGNUT View Post
    .... bronze ..... i'm pretty sure there are some types that also include zinc?
    dave
    AFAIK except for gunmetal, which sometimes has a bit of zinc, the only 'bronzes' which have zinc are more properly classified as brasses, such as Naval Brass which is sometimes called Naval bronze (it has a smidgen of tin but masses of zinc), and Silicon Bronze aka Everdur, which doesn't necessarily have zinc although it's allowed to have a bit. It has no tin so it definitely cannot be a true bronze.

    I'm no expert on this though, so am cheerfully prepared to be contradicted if I'm talking nonsense.

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    The commen bearing bronzes have between 4 and 7 % of Zinc Tin and Lead in them
    For example RG5 (din 1705) has 4- 6% of zinc 4-6%lead 4-6%tin and 83-87% copper

    The deffinition of bronze I know is it needs to have some percentage of tin
    It often is hard to tell the difference

    Peter from holland

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    Here is some interesting data that might help:

    http://www.metalreference.com/Forms_Copper_Alloy.html

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    Quote Originally Posted by aluminum View Post
    Here is some interesting data that might help:

    http://www.metalreference.com/Forms_Copper_Alloy.html
    GREAT Chart!

    Thank you..

    Regards,

    Stan-

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    You know how brass is always "kinda grabby" when using any sort of pointed tool into the work. It will pull your tool into the work. Does bronze behave that way? Or is it different?

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    "It says bronze drill chips are stringy. Whereas brass is flaky."

    I think either they got this backwards you got it backwards. I have never milled, turned, drilled or in any way machined bronze and had it ome out in strings. That was going to be my suggestion... If it creates crumbs instead of strings, it's bronze.

    You will also find those chips are basically fishhook shaped, complete with barbs. You will regularly embed one in your body any time you work with it. They go absolutely everywhere, unless you can hold them at bay with a properly placed rag, brush, or sheet metal guard.

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    If you don't "know", then short of chemical analysis, all you can do is guess. There are so many different types of copper alloys that the line between brass/bronze/copper can get pretty hazy and overlaps quite a bit. For a very general but probably as close as you are going to get without chemicals:
    Gummy & distinctly red= copper
    Not gummy but still sort of soft and gold-ish in color= brass
    Not gummy and seems pretty tough, gold to slightly red in color= bronze
    Red and darned hard and tough= possibly BERYLLIUM copper (put on your respirator)

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    Quote Originally Posted by Mike C. View Post
    "It says bronze drill chips are stringy. Whereas brass is flaky."

    I think either they got this backwards you got it backwards. I have never milled, turned, drilled or in any way machined bronze and had it ome out in strings. That was going to be my suggestion... If it creates crumbs instead of strings, it's bronze.
    I was going to say the same thing. Mike C. is right about this.

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    Take it to a larger scrap yard in your area. Most of them now have Niton (sp?) guns. They place the point of the gun up to the material and with a non-destructive test it tells you in a matter of seconds what material it is. I even see some of the more succesful scrappers at the auctions carrying them.

    When you see a scrapper with one of these at a sale,two things are possible. Either he knows what he's doing or he just stole the gun. I understand they are about $30K a copy.

    Craig Donges

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    Quote Originally Posted by Mike C. View Post
    "It says bronze drill chips are stringy. Whereas brass is flaky."

    I think either they got this backwards you got it backwards....
    I dbl checked and that is the info printed in the liked article. I guess the author had it backwards.

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    Quote Originally Posted by morsetaper2 View Post
    I dbl checked and that is the info printed in the liked article. I guess the author had it backwards.
    I've only worked with bearing bronze and such like bronze oillite, ect. I would say the maching I did on it it acted more like a non-ductile cast iorn or cast aluminum. That type of chip anyway. Maybe some of these other bronzes mentioned act differntly?

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    Quote Originally Posted by Troup View Post
    Aluminium bronze is a prince among bronzes, arguably exceeded (for most purposes) only by Nickel Aluminium bronze which is pretty much the king.

    They're outstandingly tough, hard wearing, damn strong, and pretty nice to machine.

    Also Alu Bronze is a particularly nice colour, nicer than PB :-)
    Thanks Troup, that eases my mind!
    I'll save the phosphor bronze for a more fitting project.
    And thanks for the link to the info table, aluminum, pretty & useful!
    Last edited by DazedConfused; 04-13-2009 at 02:27 PM. Reason: British spelling!


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