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  • Metal for lathe change gears...?

    I need to cut another change gear for my CQ62301 Chinese generic 12x36 lathe. Is steel acceptable material or should I seek out some cast iron bar?
    Thanks.

  • #2
    Yes it is and so is aluminum too.
    Amount of experience is in direct proportion to the value of broken equipment.

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    • #3
      If it will only be for occasional use, as in a home shop, then almost any metal will work; and many plastics, and hard woods, and other things too.

      If it will be for heavy, daily use then I bow to the advice of others.
      Paul A.
      SE Texas

      And if you look REAL close at an analog signal,
      You will find that it has discrete steps.

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      • #4
        I agree with Paul, most anything in the scrap box. I made an 11 piece change gear set and used about the whole gamut of material scrounging up that many blanks.
        If everything seems to be going well, you have obviously overlooked something........

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        • #5
          I have used al. 6061 t6 which I am sure will outlast me. Also used al/brass for change gears and a set of split nuts. All doing fine.
          Jim

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          • #6
            My lathe, a (Clausing- Colchester), has one intermediate gear that is made of canvas based phenolic resin and had worked fine for the past 30 years. It holds the lube and reduces noise.

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            • #7
              I made a set of gears ₣or metric threads out of PVC , very durable and easy to cut by slotting with a form tool. PVC was sourced from discarded 12inch sewer drain pipe.

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              • #8
                I vote for aluminum. Do your gear cutters a favor. They will return it with long life. Not to mention the lack of banging everything will take vs. using steel.
                Wayne

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                • #9
                  Thanks for the advice. I spent ages making a steel blank and cutting the key slot but I am thinking I will put that away for some other use, one day! I have black and I have white unknown engineering plastics and I have aluminium to experiment with.

                  This is a 22 tooth pinion which I expect gets a hard life so maybe I will make a couple while I am at it.
                  Last edited by The Artful Bodger; 02-04-2014, 10:48 PM.

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                  • #10
                    7075 would be a good choice

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                    • #11
                      Originally posted by The Artful Bodger View Post
                      Thanks for the advice. I spent ages making a steel blank and cutting the key slot but I am thinking I will put that away for some other use, one day! I have black and I have white unknown engineering plastics and I have aluminium to experiment with.

                      This is a 22 tooth pinion which I expect gets a hard life so maybe I will make a couple while I am at it.
                      As usual I'll take the other road. If you make the setup and figure the math for the gear, the material is inconsequential...you're going to make it anyway. Plastic and UMHW are cool as well as phenolic, but since you're set up, why not make it out of steel. This material will last longer, you'll only have to make once and you probably have something in your scarp bin that will fit the bill. My two cents.

                      Stuart

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                      • #12
                        I just had one of those thoughts, you know you can make leadscrew nuts by heating a peice of thread and pressing plastic half nuts on, aka Evanuts, could you make a plastic blank then rotate a heated gear into it to melt the plastic to a gear shape, on a pair of studs say,
                        Mark
                        Ps assuming no dividing head available etc

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                        • #13
                          yep, may as well use 1018 cold rolled, it will last, will cut decently, cheap, no good reason not to.

                          Aluminum can be used, but it isn't any prize to cut in some alloys, although 7075 is nice to work with. Some are stringy and nasty.

                          Plastics.... well OK, but I'd not bother. Some of the better ones yeah, but steel is way cheaper, and a lot of plastic cuts like crap. If you have the right stuff, I guess so.

                          I'd go on the basis of what I could cut the keyway in. That's harder than the tooth cutting.
                          CNC machines only go through the motions

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                          • #14
                            Change gears don't see a lot of force unless the carriage is crashed. Many manufacturers insert a micarta gear in the gear train as a sacrificial gear in the event of a jam.

                            Terry Sexton in HSM many years ago wrote up a method of making an emergency change gear using plywood and Bondo. He ran a strip of shimstock through a pair of gears to create a corrugated "rack" of the proper form. He then wrapped the "rack" with the proper number of teeth around a plywood blank of the requisite diameter and filled the voids with bondo. AIR, the plywood blank had steel or other suitable material for the hub.
                            Jim H.

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                            • #15
                              I just got done making three change gears for my Victor 1640 which enable me to cut metric threads. One 70T, one 35T and one 30T gear. I made the blank for the 70T gear out of 4150 annealed because that's what I could get locally as an inexpensive drop. The 30 and 35 were made from a short bar of 1144 that I'd bought from the same local source, though it turned out the blank for the 35T gear was too small (dims given to me by a gear cutter vendor), and the fellow in Woodinville WA who cut the gear teeth for me (I have no dividing head nor 20PA 1.75 cutter) made a new blank out of something he didn't specify. It could be Durabar, could be 1144. He did ask me NOT to make my blanks out of 1018 because it leaves a horrible finish on cut teeth. Hobbed or broached teeth my be better.

                              Having no idea how long I may use the gears, I didn't want to make weak ones and have to do it twice (or more.) I broached the 6mm keyway when it was done. To do that I had to borrow a broach from a friend and make a bushing for the 20mm gear blank bores.



                              If I need the gears for the 1/2 dozen threads I'm doing now or for thousands of parts (not likely), the gears will hold up. I didn't consider making aluminum, brass or plastic gears because I'm not worried about "what could happen" any more than the original machine maker did when they built the machine. The friend I borrowed the broach from has the exact same lathe and his gears are steel.
                              Last edited by PixMan; 02-05-2014, 10:22 AM.

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