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  • Another gear question

    If you lap a set of gears together with diamonds, can any embedded diamonds be completely removed by heating the gears in an oxygen rich environment?

  • #2
    Originally posted by elf View Post
    If you lap a set of gears together with diamonds, can any embedded diamonds be completely removed by heating the gears in an oxygen rich environment?
    Probably, but the temperatures required would probably melt or at least damage the gears if theyre made from something like brass, and burn the carbon out of steel. Seems like the temperature needed to start burning diamond is about 1300f in an oxygen-rich environment, 200f shy of brass's melting temp but still probably not the best for it. Steel wouldnt melt, but oxidizes quickly at high temperatures, something that an oxygen-rich environment wont help much.

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    • #3
      I haven't lapped gears, but as you note general lapping knowledge says you'd turn the gear faces into laps; lapping requires a lap softer than the work so thats where embedding occurs In those very rare instances where work on work lapping makes sense, Timesaver or other garnet abrasives which supposedly break down and loose their cutting action is an option - could you use it?
      Last edited by Mcgyver; 10-20-2018, 02:13 PM.
      in Toronto Ontario - where are you?

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      • #4
        I'd like to hear more about how you see lapping gears with diamond would work. As plain gears are designed, there isn't a rubbing action between adjacent gear teeth of a set. Hypothetically it's a line contact that moves down the touching faces as they move into and then out of contact. Lapping the gear face requires some slightly different action.

        You can induce that lateral movement of faces by running a straight cut gear against a helical gear with an appropriately skewed axis. And presuming the gear you want to lap is hardened (otherwise why would you be going to so much trouble to refine the surface and geometry) you'd leave the helical gear soft so the diamond compound would be embedded there and consider it a consumable part as it inevitably wears away. Diamond would not be transferred into the face of the other gear.
        .
        "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

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        • #5
          Originally posted by TGTool View Post
          I'd like to hear more about how you see lapping gears with diamond would work. As plain gears are designed, there isn't a rubbing action between adjacent gear teeth of a set.
          that was my first thought, but according to this its a bit of both - rolling and sliding

          http://www.cscos.com/wp-content/uplo...ille-Sachs.pdf
          in Toronto Ontario - where are you?

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          • #6
            Originally posted by epicfail48 View Post
            Probably, but the temperatures required would probably melt or at least damage the gears...
            Ignition temperature for diamonds is just below the heat treating range for low alloy steels.

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            • #7
              Originally posted by TGTool View Post
              As plain gears are designed, there isn't a rubbing action between adjacent gear teeth of a set.
              Not so. There very much does exist sliding contact and is a specifically targeted quality to some extent in trains designed with purpose. If there were not, scuffing would never be of issue...

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              • #8
                Originally posted by Zahnrad Kopf View Post
                Not so. There very much does exist sliding contact and is a specifically targeted quality to some extent in trains designed with purpose. If there were not, scuffing would never be of issue...
                I'll stand corrected. You're the gear guy. Nevertheless, if you want to lap gears for correct contour and surface finish I think it should be something more thought through than run two gears together with grit.

                It is true that it may be a useful technique if the gear or gears you have are rough and the geartrain just needs to be smoothed a bit. Otherwise, a form tool lap or a lapping disk and mechanism to generate the correct contour would be a more intentional approach.
                .
                "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

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                • #9
                  Actual legitimate lapping uses a "lap gear" run against the gears. That smooths and provides correct form.

                  Lapping them together is really just "pre-wearing" them, it will not predictably produce correct form, etc. It's no better than "lapping in" the carriage of your mini lathe with abrasive powder between it and the bed. (which I have seen recommended. There is probably youtube stuff about it).
                  CNC machines only go through the motions.

                  Ideas expressed may be mine, or from anyone else in the universe.
                  Not responsible for clerical errors. Or those made by lay people either.
                  Number formats and units may be chosen at random depending on what day it is.
                  I reserve the right to use a number system with any integer base without prior notice.
                  Generalizations are understood to be "often" true, but not true in every case.

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                  • #10
                    Originally posted by Lee Cordochorea View Post
                    Ignition temperature for diamonds is just below the heat treating range for low alloy steels.
                    In high-oxygen environments yes, but the same oxygen needed for the diamond to burn will also react with the carbon in the steel, resulting in heavy decarb and scaling

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                    • #11
                      Wearing in would be a better term than lapping. It could be useful for noisy gear trains.

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                      • #12
                        Originally posted by elf View Post
                        Wearing in would be a better term than lapping. It could be useful for noisy gear trains.
                        ( assuming that you are discussing Spur Gears )
                        Only at the expense of the very reasons for utilizing the Involute form to begin with.

                        The only time that I have seen lapping ( in the manner being discussed ) specifically requested or required is for Straight Toothed Bevel/Miter Gears ( Plain & Skew variations ) and that is only to get rid of the abhorrent inconsistencies left behind of manual Form Milling in effort to create "matched pairs".

                        Otherwise, it's a poor choice for any desire to actually remedy any issues.



                        Last edited by Zahnrad Kopf; 10-20-2018, 05:35 PM.

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