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Thread: Bronze question

  1. #1
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    Default Bronze question

    I need to make six bronze portlight frames (8" x 16") for my boat. These are just flat frames that would be 3/16" thick. I have a friend who has a CNC mill that could cut these out. So I need to buy the flat 3/16" sheet stock. What alloy should I look for? I've played with naval bronze but it seems really hard, just need something that is millable and appropriate for a salt water boat.

    They would look like this (computer image).

  2. #2
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    Default Re: Bronze question

    Everdure is the most available and is workable. Naval brass is good, it drills, files and polishes well. Manganese bronze is most often used for the casting of many marine items. Stay away from phosphor and aluminum bronze as they are very hard to work and will afford nothing for the job you are doing.
    Jay

  3. #3
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    Default Re: Bronze question

    C485 "Naval Brass" or "bronze" is a "leaded" alloy and free machining.

    Like butter...

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    Default Re: Bronze question

    I just talked to Alaska Copper and Brass and they recommended 464 naval bronze. Does that sound right? A 24" x 36" x 3/16 is $393. (Ouch).

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    Default Re: Bronze question

    Hey Ron, if you do get the full sheet I'd be interested in buying the center cut-out waste pieces from you, assuming you don't have another use for them. I was thinking of using bronze plate to make a new instrument panel and the waste from your surrounds might be the perfect size. I have a few other places I'd want to use it as well.
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    Default Re: Bronze question

    Quote Originally Posted by cstevens View Post
    Hey Ron, if you do get the full sheet I'd be interested in buying the center cut-out waste pieces from you, assuming you don't have another use for them. I was thinking of using bronze plate to make a new instrument panel and the waste from your surrounds might be the perfect size. I have a few other places I'd want to use it as well.
    You might have a deal. I was thinking it would be nice to have some bronze scrap as well, but I have too many wood scraps I never use. But maybe we could just keep it in a community pot. Each center scrap would be about 6" x 14" less the width (x 2) of the milling bit.

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    Default Re: Bronze question

    You might have a deal. I was thinking it would be nice to have some bronze scrap as well, but I have too many wood scraps I never use. But maybe we could just keep it in a community pot. Each center scrap would be about 6" x 14" less the width (x 2) of the milling bit.
    sounds good to me. Size is about what I was expecting. I'll do some measuring to be sure but I think that will be just about perfect. Let me know when you are ready to proceed and let's chat.
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    Default Re: Bronze question

    I love this forum...
    "If it ain't broke, you're not trying." - Red Green

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    Default Re: Bronze question

    Quote Originally Posted by Canoeyawl View Post
    C485 "Naval Brass" or "bronze" is a "leaded" alloy and free machining.

    Like butter...
    What Jake said.
    '' You ain't gonna learn what you don't want to know. ''
    Grateful Dead

  10. #10
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    Default Re: Bronze question

    You may wish to investigate having these pieces cast instead of cutting them out of sheet stock. Most areas have foundries that can cast bronze. (Many specialize in casting art bronzes, while others do industrial work as well.) The pattern is very easy to make (check for any shrinkage allowance necessary.) You bring the pattern to them and they cast the piece for you. By making your own pattern and doing your own finishing of the rough casting, you can really cut the prices down. I could be wrong, but I expect sheet stock will be much more expensive, given that you'll be left with a fair amount of off-cuts. You can usually find a use for these over time, but still.

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    Default Re: Bronze question

    Quote Originally Posted by Bob Cleek View Post
    You may wish to investigate having these pieces cast instead of cutting them out of sheet stock. Most areas have foundries that can cast bronze. (Many specialize in casting art bronzes, while others do industrial work as well.) The pattern is very easy to make (check for any shrinkage allowance necessary.) You bring the pattern to them and they cast the piece for you. By making your own pattern and doing your own finishing of the rough casting, you can really cut the prices down. I could be wrong, but I expect sheet stock will be much more expensive, given that you'll be left with a fair amount of off-cuts. You can usually find a use for these over time, but still.
    That's where I started. I found one guy that wanted about $1000 to cast six of them if I made the plug. Then this morning I was calling around to get the number of another guy who had his own small casting foundry when another friend said he has a CNC milling machine that will easily do this; no charge if I work with him. Just the cost of the material which is about $400 plus maybe the cost of a bevel bit. Also the mill could easily drill and countersink the required screw holes.
    Last edited by ron ll; 02-21-2017 at 04:46 PM.

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    Default Re: Bronze question

    Quote Originally Posted by PeterSibley View Post
    What Jake said.
    Interesting. So when I called Alaska Copper and Brass, they said that c485 is more of an architectural brass, not naval. She suggested going with 464 which she called naval brass or bronze and said it would be more appropriate. I don't know the difference. On line both are called naval brass.

  13. #13
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    Default Re: Bronze question

    Quote Originally Posted by ron ll View Post
    I need to make six bronze portlight frames (8" x 16") for my boat. These are just flat frames that would be 3/16" thick. I have a friend who has a CNC mill that could cut these out. So I need to buy the flat 3/16" sheet stock. What alloy should I look for? I've played with naval bronze but it seems really hard, just need something that is millable and appropriate for a salt water boat.

    They would look like this (computer image).



    Here's an option that I would consider. Buy sheet stock of the required thickness. Rip or bandsaw out the straight and corner sections with an eye to TIG welding them together with two joints in each corner. Sand them flat. Make a couple of jigs to rout the outer and inner profiles. Polish.

  14. #14
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    Default Re: Bronze question

    http://www.nationalbronze.com/News/what-is-naval-brass/

    As its name implies, Naval Brass was originally developed for sea water service applications. Tin in included in the alloy composition in order to improve the corrosion resistance of Naval Brass. The presence of lead in Naval Brass assists in the machinability of the metal. C464 Naval Brass Rod has a fair machinability with about 35% of Free Machining Brass.

    The addition of Tin also gives Naval Brass a high resistance to dezincification. Dezincification is a type of dealloying in which one of the constitutes of an alloy is removed by corrosion. Dezincification was first recognized as a serious problem in brass tubes used for ship condensers around 1920. At the time this problem was referred to as “Condenseritis”. Since then various alloys have been formulated to stop this process, one of which being Naval Brass.

    Naval Brass is used extensively in marine hardware applications, but the uses don’t stop there. Its higher tensile strength and resistance to wear make it applicable in bushings and wear strip as well as fastener and valve stem applications.
    - Chris

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  15. #15
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    Default Re: Bronze question

    One resource on the 'Net indicates that C485 is more easily machined (rated 70 vs 30 for C464). They are both high in zinc content.

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    Default Re: Bronze question

    Evidently there is more lead in 485 than in 464. Not sure why she was steering me to the 464. I'll ask again before ordering it.

    Jim:
    Thanks, I had considered that, but the added labor on six pieces seems to out weigh the material cost, especially when Chris and I can probably both make use of the scrap. I already have a cad file that will run the CNC, and the idea of sitting back and watching the machine cut and drill six identical parts appeals to the slacker in me.
    Last edited by ron ll; 02-21-2017 at 07:36 PM. Reason: Brain fart correction

  17. #17
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    Default Re: Bronze question

    I had two oval portlights cast by classic marine for a very reasonable price, including shipping from UK

  18. #18
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    Default Re: Bronze question

    I am sort of familiar with the lead thing for a couple of reasons, one being machining, and the other being historical marine components where leaded brass makes good parts (gears, etc) which can stand only periodic oiling rather than submersion.

    I don't think your application will know the difference, but the machinist will! The dezincification on parts like yours is most critical in the fasteners, I would use silicon bronze fasteners.

  19. #19
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    Default Re: Bronze question

    Try reaching out to a Laser / Waterjet cutting shop that specializes in alloys. They often nest smaller pieces for other work inside drops. You might have to wait until they have other bronze cutting work

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    Default Re: Bronze question

    In case you haven't found a shrinkage factor yet, we used 3/16" per foot for Brass, Bronze, and "Nickeloy" (silver-colored Bronze alloy) plumbing product castings at Josam back in the 1970's. You'll find Josam products on the floors of public restrooms where you see Wade and Zurn these days. Polished surfaces had 1/16" added to that.

    Ten years ago I worked for a manufacturer of door and window hardware. One Designer and his Engineer Department Supervisor designed a big-ticket brass entry door pull forging and did not include any polishing allowance. Of course the finished product was weak due to insufficient sections. When I questioned (as an interested bystander) about what they'd used for a polishing allowance, neither knew what I was talking about.

  21. #21
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    Default Re: Bronze question

    Quote Originally Posted by ron ll View Post
    Interesting. So when I called Alaska Copper and Brass, they said that c485 is more of an architectural brass, not naval. She suggested going with 464 which she called naval brass or bronze and said it would be more appropriate. I don't know the difference. On line both are called naval brass.
    Naval brass is a group of six alloys with 60%Cu, 39.2Zn and 0.8%Sn. C464000 is uninhibited, C46500, C46600 and C46700 contain a small amount of As, Sb or P to prevent dezincification. The mechanical properties are almost identical. Machinability is 30% of free machining brass. C48200 is medium-leaded naval brass and C48500 is high-leaded naval brass with machinability ratings of 50 and 70% respectively.
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

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    Default Re: Bronze question

    Thanks Dave, that's very helpful. I think I'll hold out for the 485, unless it's cost prohibitive.

  23. #23
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    Default Re: Bronze question

    Quote Originally Posted by ron ll View Post
    I need to make six bronze portlight frames (8" x 16") for my boat. These are just flat frames that would be 3/16" thick. I have a friend who has a CNC mill that could cut these out. So I need to buy the flat 3/16" sheet stock. What alloy should I look for? I've played with naval bronze but it seems really hard, just need something that is millable and appropriate for a salt water boat.

    They would look like this (computer image).
    For whatever itīs worth....:

    Iīve used naval aluminium for the rims on 6 windshield glass-panes. The rims (integral) were cutout with a water-jet contraption in a speciality shop, and in succession powder-oated to a coloring similar to what you have posted, less the gilt-hue.

    Much cheaper than using any brass, let alone bronze, specially when one sees no immediate use for the sheeting that is left over.

    If you are at all interested, I could look up the correct spec and let you have the left-overs, provided you handle shipping and clearing at customs.

  24. #24
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    Default Re: Bronze question

    Thanks, I really appreciate the offer. But I'm not a big fan of aluminum (even coated or anodized). The bronze is a bit pricey but not out of the question, and I think more appropriate for Snoose. Plus I think between Chris and I, we can find use for the scrap.

  25. #25
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    Default Re: Bronze question

    Quote Originally Posted by carioca1232001 View Post
    For whatever itīs worth....:

    Iīve used naval aluminium for the rims on 6 windshield glass-panes. The rims (integral) were cutout with a water-jet contraption in a speciality shop, and in succession powder-oated to a coloring similar to what you have posted, less the gilt-hue.

    Much cheaper than using any brass, let alone bronze, specially when one sees no immediate use for the sheeting that is left over.

    If you are at all interested, I could look up the correct spec and let you have the left-overs, provided you handle shipping and clearing at customs.
    OP isn't interested (it's his boat), but someone else might be. ASTM B928
    http://www.aluminum.org/sites/defaul...porttheMar.pdf
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

  26. #26
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    Default Re: Bronze question

    Fair enough !

  27. #27
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    Default Re: Bronze question

    How about G10, the glass-epoxy laminate?
    For same size, it's a fraction of the cost if bronze.
    Needs painting.

  28. #28
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    Default Re: Bronze question

    Another option would be to use flat stock that you cut to length and have welded at the corners, then round the corners to whatever radius you want. Bronze welding rod comes in a variety of gauges and is about $20 for a one pound tube, which is more than you need. You would end up with less wastage this way, and it would be plenty strong enough for your application. I'd be given my walking papers if I tried to sell any here, but I have more 1/4" x 1 1/2" flat stock than I need.

  29. #29
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    Default Re: Bronze question

    Thanks Train, but I've a friend who is anxious to use his CNC mill on this little project and I think I can find a good use for the "waste" of the sheet stock. Plus the project has been put on hold while my boat is hauled out and waiting for the Seattle rain to stop, which should be about July 5th.

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