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Thread: Sorting through old screw bins. How to tell silicon bronze from brass?

  1. #1
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    Default Sorting through old screw bins. How to tell silicon bronze from brass?

    I was given a good size assortment of marine hardware, and some of the screws are obviously proper silicon bronze boat screws. They have a dark almost green copper patina and most have slot heads. Some of the smaller wood screws are Phillips head and look a little too shiny to be bronze. They look to be brass maybe. Is there a common way to sort through these screws and separate them?
    Thanks folks!

  2. #2
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    Default Re: Sorting through old screw bins. How to tell silicon bronze from brass?

    Silicon bronze can be quite shiny when untarnished. The "Phillips head" is more likely a Reed & Prince aka Frearson head on either metal. It shouldn't fit a phillips driver properly. If you remove some of the tarnish (with scotch-brite or similar), brass has a more golden color whereas bronze tends to be more red. Of course, there are a variety of bronzes and brasses, so it's hard to be 100% certain if something is silicon bronze or not.

  3. #3
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    Default Re: Sorting through old screw bins. How to tell silicon bronze from brass?

    Just put them in salt water for a while. The brass ones will disappear.

  4. #4
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    Default Re: Sorting through old screw bins. How to tell silicon bronze from brass?

    Or drive hem into a properly bored hole in hardwood. The brass ones will shear off.

  5. #5
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    Default Re: Sorting through old screw bins. How to tell silicon bronze from brass?

    I have had the same delema as you a number of times. There is a boat builder /repair guy in RI who makes videos "Hints from a boat builder" or something like that who showed a way to pretty well tell the two apart (want to give credit where it is due.). (I was sceptical at first, but it seems to work pretty well.) If you drop them on a concrete floor and listen to the ring, bronze being harder makes a sharper more clear ring. Brass is a bit more of a dull tone. I use that in conjunction with looking at them.

  6. #6
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    Default Re: Sorting through old screw bins. How to tell silicon bronze from brass?

    Quote Originally Posted by nedL View Post
    I have had the same delema as you a number of times. There is a boat builder /repair guy in RI who makes videos "Hints from a boat builder" or something like that who showed a way to pretty well tell the two apart (want to give credit where it is due.). (I was sceptical at first, but it seems to work pretty well.) If you drop them on a concrete floor and listen to the ring, bronze being harder makes a sharper more clear ring. Brass is a bit more of a dull tone. I use that in conjunction with looking at them.
    A good tip!

    360 Brass (Free Machining Brass)
    C360 Free Machining Brass
    Minimum Properties Ultimate Tensile Strength, psi 58,000
    Rockwell Hardness B78
    Chemistry Copper (Cu) 60 - 63%
    Zinc (Zn) 35.5%


    Silicon Bronze
    Silicon Bronze, C655
    Minimum Properties Ultimate Tensile Strength, psi 85,000
    Elongation in 2" 20%
    Rockwell Hardness B90
    Chemistry Copper (Cu) 97.0% min

  7. #7
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    Default Re: Sorting through old screw bins. How to tell silicon bronze from brass?

    Tips From A Shipwright Louis Sauzeede but I can't find the video....oh, and price

  8. #8
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    Default Re: Sorting through old screw bins. How to tell silicon bronze from brass?

    In the do as I say not as I do department, you might try the vinegar test:
    http://forum.woodenboat.com/showthre...Silicon-Bronze

    The old Lydian stone trick comes to mind, but you will need to see if the color difference is good enough to tell.
    http://straightrazorplace.com/hones/...ian-stone.html
    The lydian stone is hard, black and acid resistant, so it works by giving a good color contrast and survives a lot of testing without regrinding the surface.
    Lydian is basinite is similar to novaculite. Black novaculite is a good grade of Arkansas stone, so if you want to pay more than the screws are worth to try a scratch test on something more durable than 600 grit wet or dry paper, the stone will be a good addition to your sharpening tool kit. http://www.naturalwhetstone.com/productssharpening2.htm

    I would toss the screws in a plastic colander and pour some muriatic acid or Tarn-x over them hoping to get a discernible color difference.
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

  9. #9
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    Default Re: Sorting through old screw bins. How to tell silicon bronze from brass?

    Thank you everyone for the good tips and ideas!

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