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Turning copper

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  • #16
    I have to agree with mochinist. I never heard tell of using milk on copper till I came to this board and I've been in the business 40 years. Totally agree with just using a kerosene and oil mix off a paste brush. I've done it often myself and it managed to get the job done efficiently.

    With regard to the "warm spit" post : An old guy I worked with long ago mentioned a machinist he worked with when he was a just starting out in the trade who chewed tobacco. He said the guy was so proficient in the use of tobacco spit as a cutting lubricant that when threading he could hit the thread just in front of the tool as it was cutting from his normal standing position at the lathe. Said he saw him do it often with his own eyes and that the guy never missed. The guy who told me this was pretty much a straight shooter so I believe his story.
    Last edited by DATo; 09-23-2011, 03:54 AM.


    • #17
      Sorry guys, haven't visited in a few days, little busy. A few answer to questions asked, and other clarifications.

      1. Diamond has an affinity for copper so it just "sticks" to it. It gets impressed into the metal and just stays there. Makes it easy to create and use your own cutting heads. Wouldn't try to mill a battleship out of a single block of steel, but it works wonders at the smaller scale.
      2. I am using my creations primarily for fantasy cutting. For those not familiar, that is the art of placing dimples, V channels, U channels, and other forms on the surface of a stone. For what I like to do, no one makes what I need, so I need to make my own. Hence the lathe, and the questions about turning copper.
      3. My heads will be less than 1" in diameter (a ball, wheels with rounded edges of different radii, wheels for creating a V with different side wall angles, etc), the shaft can be up to 3/8" diameter. To create a head attached to an arbor, I can do solder, milling out of solid stock, drilling and tapping to insert and end screw similar to Dremel, anything is possible. I care about the destination (finished product), not the trip itself (process to make it). So I wanted to see what you guys recommended.

      So, from what I gather, copper gums things up (already knew that). The use of a cutting liquid, ranging from milk to petrol products to whale blubber to fairy wings would probably work, I just need to see what works for me. Not unusual, every gem cutter cuts stones, and every one of them does it differently. Same things you pros go through, we just work rock and not metal.

      For a good finish, use high speed and a light touch.

      So I shall experiment, and if anyone can recommend a good book on metal machining (I can actually read AND look at pictures!), I would be greatly appreciative. Send the suggestion to [email protected] if you would please, I don't do much web blogging.

      Thanks for your inputs.



      • #18
        Originally posted by Video Man
        +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.
        Add a tablespoon of powdered graphite to the lard and kerosine.
        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.


        • #19
          Not knowing exact details and that the end product it the thing, for you, I would suggest not duplicating items already out there that may be close enough


          that is just a quick found example from Lee Valley,
          Suitable for all woods, hard metals, bone, alabaster, glass, gemstone and plastic, the bits keep their shape, even when working metal
          and that is without any looking at jewelry sites.

          At the very least a look at the general shapes of those and other types of burrs could give you ideas as to what is needed or what is just nice but seldom used (there are what, 100s of shapes ? in mounted points for example but only maybe a couple dozen have common usage, rest are used but only for specialized needs)


          • #20
            You will probably find that copper cutters are a bit slow, even with coarser diamond, especially for the "V" grooves where it is difficult to hold a sharp edge.

            You probably will have better luck doing your initial grooves with diamond coated (or scintered) "V" or "U" shaped little wheels which some lapidary shops make. They do leave quite a bit of "subsurface damage" and later need more work to remove the scratches in the gem material. The the finer work can then be done with other kind of materials like copper. If you are concaving, copper rods stiffened with steel inserts (if the your cutters are thin) works well, but are slow.

            If you are using shaped copper discs for your cutting, you will need to change them often due to the copper becoming misshaped. You might consider a small sort of arbor, like dremel has, where you drill your copper and then change frequently on the arbor.

            The grinding wheels which RussZHC suggested will not hold up for very long under lapidary use.

            You biggest challenge will not be cutting the shapes, but polishing.
            Last edited by davidwdyer; 09-25-2011, 06:11 AM.
            VitŮŽria, Brazil