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I Can't Believe Cored Bronze Round Moved

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  • I Can't Believe Cored Bronze Round Moved

    I made these two rings to cut the weight segments out of for my balancing hubs. I measured them to the tenths on the ID & OD.
    After I cut the first ring from the bar I noticed when I put a ground parallel across the faced end that it had moved. The inside edge raised slightly in a few spots. I could also feel it move when I set it on the surface plate.
    I've had this issue when making similar parts out of steel but didn't expect it to happen with 932 bronze.
    The rings also went out of round by about 1.5 thou. None of this will matter since the weight segments won't be much longer than a 1/2" but what if it was something that did matter like a bearing or sleeve.

    Now I have to face the opposite side down to the appropriate thickness.
    Lastly............ what do I do with the 3 Lbs. of turnings?????? Hate to scrap it. Maybe I can melt it down into something useful like a piece of bar for the next project.

    JL................


  • #2
    Everything moves and/or is made of gum rubber. Cast stuff moves the most, When machining something cast I usually rough things in and leave it overnight before finishing, and even then I've seen cast iron casting move .006" across a 1.5" bore.

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    • #3
      As for the turnings... I do some considerable work in brass and bronze. I used to sweep and toss the turnings, no longer. Save all the turnings and scrap and it goes to the salvage yard, $1.10 per pound. Oh' be sure to thoroughly clean your machine of any steel residue before beginning the brass/ bronze work. If the scrap man's magnet picks up anything, you loose big on the price.

      Joe B

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      • #4
        I think you weill need more chips....but this cast apple is sort of neat....

        https://www.youtube.com/watch?v=4pdjg3a1amM
        in Toronto Ontario - where are you?

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        • #5
          Originally posted by rkepler View Post
          Everything moves and/or is made of gum rubber. Cast stuff moves the most, When machining something cast I usually rough things in and leave it overnight before finishing, and even then I've seen cast iron casting move .006" across a 1.5" bore.
          It didn't move until I cut the ring from the round. At this point it's not going to return to post cutting dimensions. In this case it's not going to matter and I can't change the ID or OD.

          JL..................

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          • #6
            I'm told that swarf doesn't really cast all that well because the metal has so much surface area that it tends to oxide heavily at melting temperatures and you lose a lot to slag. That's not to say that if you had a lot of turnings you couldn't make up for losses by adding more to the crucible though.

            The other problem is having a furnace that's gets hit enough to melt copper and bronze.

            Sent from my SAMSUNG-SM-G900A using Tapatalk

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            • #7
              In my experience, bronze is the worst as it always moves, warps, twists in some form or fashion, fortunately is this case the pieces are still usable..

              Very nice work on the entire project!

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              • #8
                In the future it might help to run a raw block thru a heat cycle to normalize internal stresses.

                If you want to melt down the swarf, put a cover over the metal in the crucible - like a layer of crushed charcoal. Helps cut down on the oxidation.

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                • #9
                  It sounds like it's not worth the time and effort. I had thoughts of perhaps melting it down and casting a small bar that might come in handy for a future project. There may also be some steel swarf in the mix. I may be able to pick it out with a magnet but if I don't get it all I'm not sure how it will come into play in the mix. Will it separate from the molten bronze???
                  The other thought that occurred to me after watching the video of the guy casting the apple is I may end up with a lot of voids in the bar which would make it unusable in most cases. Not sure if it changes the strength or integrity of the material either, and I would probably use more gas to melt the stuff that it's worth.

                  JL.................

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                  • #10
                    Does anyone have any ideas on how I can fixture each weight segment after I rough cut each one out of the ring????

                    After I cut each segment out I would like to make sure each one is the same size and the angle cuts are the same.
                    I need some thoughts on how to set up to do this.

                    JL.................

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                    • #11
                      Originally posted by JoeLee View Post
                      Does anyone have any ideas on how I can fixture each weight segment after I rough cut each one out of the ring????

                      After I cut each segment out I would like to make sure each one is the same size and the angle cuts are the same.
                      I need some thoughts on how to set up to do this.

                      JL.................
                      Center and clamp it to a rotary table. Run a thin endmill through it to make a cut. Crank the table 120 degrees, add clamps if necessary, and
                      make the next cut.
                      Location: Long Island, N.Y.

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                      • #12
                        I thought of this but I don't want to remove the chuck from my RT and go through all the set up. Got to be an easier way.

                        I can scribe the lines and was thinking of clamping the ring in the mills vise and slicing through it with an .020 slitting saw.
                        However this still presents an issue as far as getting the angles all the same and the length of each segment the same.

                        JL..............

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                        • #13
                          Originally posted by JoeLee View Post
                          I thought of this but I don't want to remove the chuck from my RT and go through all the set up. Got to be an easier way.

                          I can scribe the lines and was thinking of clamping the ring in the mills vise and slicing through it with an .020 slitting saw.
                          However this still presents an issue as far as getting the angles all the same and the length of each segment the same.

                          JL..............
                          Then carefully chuck up the ring and make scribe marks 120 degrees apart. You can do this on the lathe or rotary table. Now you should be
                          able to clamp it in the vise and and line the scribe lines up with the slitting saw.
                          Location: Long Island, N.Y.

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                          • #14
                            Yes, that is the way I had originally figured I would have to go about this without getting too elaborate.

                            The other thing I was wondering about was how big or long should I make each weight?? I know that in this case it's not size that matters but the weight of each segment, weather they are all perfectly equal shouldn't really matter.
                            I do know that even one segment that is about 1/2" long is probably five times heavier than any 7" x 1/2" wheel could be out of balance.
                            But this is relatively new territory for me. I'm pretty much going by what I see in other manufactured hubs.

                            JL...............

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                            • #15
                              Three pounds of chips, lots of actaul labor, elaborate setups, more tooling. Why CNC is making more and more sense for the home shop! About 15 minutes to draw this and program in CamBam, then watch it cut. I get it, you aren't in a hurry, but it is nice to finish minor stuff quickly so you do more interesting projects. CNC is getting cheaper all the time at a very fast rate right now due to the influence of 3d printers.

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