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Machining Bronze

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  • Machining Bronze

    I have a P.M. steam engine kit that has bronze castings. I will be turning these parts on the lathe, and will be milling some also. My question is-- what is the correct type tooling to use on the bronze? My lathe has indexable carbide. The mill has high speed steel cutters.

  • #2
    There's about a gazillion "bronze" alloys, so it's hard to say for sure. In machinability, bronze (depending on the alloy) runs the gamut from not too bad to difficult. You'll just have to try the castings to see what you have. Presumably, whoever made the castings had some interest in making them machinable.

    *Sharp* tools are always good, especially so with bronze. I haven't tried carbide on bronze, but I'd guess that you'll do better with hss.
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    • #3
      Would depend on the size of your piece/rigidity of your setup and the type of bronze you are cutting. We use either HSS or carbide at work for this. Profile tools are very much HSS and most else is carbide.


      • #4
        Just did some .75 bore x 1.625dia.x4"bushings for a machine.
        Treat bronze like brass. Used a cheap carbide boring bar for the bore. Make sure your drill is ground for plastic or brass (flatten the cutting edges about .031 to prevent grabbing.
        Used a HSS cutting tool for turning ground flat-top, horizontal to the bed like import carbide tooling to prevent grabbing. The pucker factor of back raked tooling in brass, bronze,or hard plastic is a 9!. If you don't want to ruin a drill by flatting the cutting edge, you would be best to really have a solid (read solid and locked set up,) and drag on quill or table. If you have ever drilled almost through a thin piece of metal and had the drill grab, understand that these materials do it during the whole cut. Remember also, those cheap imported boring tools and many others work as a single flute drill if the central corner of the carbide is at center of the starter hole to be bored in the stock.
        good luck
        To know by reading is different than knowing by doing. OR:
        What you have going into a situation is knowlege..What you have coming out of that situation (providing you survive!) is wisdom.


        • #5
          It's a fair bet that your castings will be gunmetal - leaded bronze. In which case HSS or plain high carbon steel is fine. I have always used tools shaped for mild steel in cutting bronze castings in model enginering applications.

          Drills tend to grab badly in gunmetal so keep things tight and go gently. Flattening the drill lips helps as others have noted.


          • #6
            Thanks for the replys guys.

            I go a little easy, especially when drilling, and will let You know how the carbide goes.