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  • Turning copper

    I have a Taig Model 4500 Micro Lathe and am new to turning metal. I got it to make specialized copper grinding heads for gem cutting. Copper is a bit of a pain as I'm sure you all know, but I have a few basic questions for the more experienced:
    1. Should I use HSS or some other material for the cutting head?
    2. RPM - I need a good, smooth finish. Go as fast as possible?
    3. If I wanted to make a 1" diameter wheel on a 1/4" diameter shaft, and I don't want to turn down a 1" rod, how would I attach the two pieces?

    I need to use copper as I will diamond impregnate it for grinding purposes, and it sucks up diamond like a sponge in water.

    Can't tell you if it is hard or soft copper, if the two are different I'll take suggestions for both. Can always email me at [email protected]. Any help greatly appreciated, my skills and knowledge are in working stone, not metal. I have skills in "materials management", but still treat me like I don't know nuthin' and let's go from there. Thanks!

    Scott

    So much to learn, so little time!

  • #2
    3] I'd be tempted to solder a copper "disc" to steel (?, sorry not enough experience to specify material)

    Machinery Handbook keeps it simple, "Copper can be turned easily at 200 feet per minute."

    Atlas "Lathe Operation" gives a bit more detail, highlighted by:
    ...combination of toughness and softness...recommend tool angles as Front relief 12*, Side clearance 14*, Back rake 16.5*,
    Side rake 20*...turning speed recommended at 120 sfpm or slightly less for wide face tools...fine finish cuts at .0035 inch feed w DOC of .030 to .050 for roughing and finishing about .010...round nose tool w 1/16 radius for finishing and edges honed as sharp as possible...chips will be tough and stringy...cut-off on soft copper is difficult as the chip wants to spread and jam in the groove... [tooling HSS]
    [FYI: AFAIK neither is specific as to type of copper ("Ops" does talk about harder copper alloys later), I am assuming neither is discussing beryllium copper...whole different kettle of fish from what I have heard]

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    • #3
      Russ is onto something. Make yourself an arbor and be able to change wheels. You will need a positive location method, which is this biz means a tapered fit. What SFM are we talking about here?

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      • #4
        When you've gotten your answer I wonder if you could elaborate on your diamond-sucking copper experience There has to be something interesting about that. I have a feeling if copper can suck up diamonds then it should also hork garnet as easily. I have several buckets of garnet blasting media and am always looking for interesting ways of using it.

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        • #5
          I asked this question of an "old timer" when I got my first copper job long ago ... his answer: "Keep it wet."

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          • #6
            Originally posted by DATo
            I asked this question of an "old timer" when I got my first copper job long ago ... his answer: "Keep it wet."
            ...... with milk!
            Tel

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            • #7
              I can't exactly tell if your 1/4" is the working part or the 1" part, but I assume that it is the 1" part. I think you might consider drilling out the copper and pressing a 1/4" steel shaft into the copper for two reasons.

              First, it is easier. And second, if you are putting pressure on the 1" part with a 1/4" copper shaft, the shaft will bend.

              Are you doing concave faceting or something else?
              VitŮŽria, Brazil

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              • #8
                Cut with honed HSS tools (Sod Carbides), radiused end, cut fast and wet - Milk or WD40 or even Parraffin.

                Instead of bar stock, you could Silver Solder (British terminology) blanks from sheet to a smaller dia mandrel, which is going to anneal it anyway and turn to a disc.

                Regards Ian
                You might not like what I say,but that doesn't mean I'm wrong.

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                • #9
                  1. Should I use HSS or some other material for the cutting head?

                  2. RPM - I need a good, smooth finish. Go as fast as possible?
                  3. If I wanted to make a 1" diameter wheel on a 1/4" diameter shaft, and I don't want to turn down a 1" rod, how would I attach the two pieces?

                  HSS is fine. Keep it sharp,SHARP. I had good experience grinding my tooling the same as for alum.


                  As fast as alum. Copper is a lot 'gummier' so a finer feed is called for.


                  Silver solder the copper. Steel, brass, stainless, it doesn't matter.


                  If I were doing it I'd ss the blank to its shaft and then machine the copper to the final dimension.

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                  • #10
                    Maybe its because the smell of rancid milk makes me gag, but I've never understood the fascination of home type machinist wanting to use milk on copper. It will no doubt help and be better than trying to turn/mill/drill the copper dry, but you could also use water soluble coolant/wd-40,kerosene, or even plain ol cutting oil and not have rancid milk all over your machine.

                    When the milk thing may have been more common(whale oil and lard also for tapping) I dont think they had as many options as we do now. I would imagine all of the above would also attract critters to your machine.

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                    • #11
                      Turning copper is a pain, if you have a hard drawn alloy a lard,graphite,turpentine,cutting oil mix may be needed.Whole milk works well the fat helps keep your edge lard,milk, whale oil high fat types work best.Cutting tools with a positive rake seam to work best.To anneal it heat then quench.For a material that is supposed to be soft this stuff will dull your tools and ruin your day until you find the right cutting oils and tool combo.
                      Make a steel shaft with a tapered end with a nut on the end as your soft copper diamond imbedded tool wears tighten the nut.
                      I never trust a fighting man who doesn't smoke or drink.
                      William Halsey

                      As a Machinist & Gunsmith I like to hear how to not can't do. P.A.R.

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                      • #12
                        Originally posted by mochinist
                        Maybe its because the smell of rancid milk makes me gag, but I've never understood the fascination of home type machinist wanting to use milk on copper. It will no doubt help and be better than trying to turn/mill/drill the copper dry, but you could also use water soluble coolant/wd-40,kerosene, or even plain ol cutting oil and not have rancid milk all over your machine.

                        When the milk thing may have been more common(whale oil and lard also for tapping) I dont think they had as many options as we do now. I would imagine all of the above would also attract critters to your machine.
                        Perhaps 'cos the milk works so well!

                        Hmmm..... 'and arf a pint of whale oil please!' - in this country you'd probably get lynched!
                        Tel

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                        • #13
                          Originally posted by Tel
                          Perhaps 'cos the milk works so well!
                          I dont know, I've been turning, milling and drilling copper for years and never had any problems using the modern methods and no rancid milk smell to deal with. Drilled a bunch of .025" holes .5" deep in 101 copper yesterday, using a acid brush and some kerosene.

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                          • #14
                            Possibly with a heavier machine? Mine is a Myford ML7.

                            I use kerosine, or WD40 for aluminium, but have never had much luck with copper. Another thing that works OK with copper, tho', is a smear of Trefolex paste - but I didn't say that, it tends to give off nasties if you get it too hot.
                            Tel

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                            • #15
                              +1 on what P.A.R. said, I've been playing lately with making lard oil compounds from lard oil extracted from grocery-store unsalted lard. (Another post for another time). Tried a mix of lard oil and turpentine on brass, copper and aluminum bronze and was amazed at the quality of the finish with all of these on lathe turning. Slightly round-nosed tools, rake appropriate for the material. Non-staining oil, and gleaming smooth finishes....mixed with kero, it works great on steel, and with trichlor (don't ask...) makes the greatest aluminum threading and reaming results I ever accomplished. One poster here referred to one of the new synthetic threading compounds as "about as effective as warm spit." Maybe those ole boys back in the day really knew what they were doing....

                              The mix is not a lot of help drilling aluminum bronze, however, it still binds and squeaks.

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