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CNC machined change gear for Atlas Lathe

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  • CNC machined change gear for Atlas Lathe

    Well I got antsy and wanted to see if I could just machine the gear using standard tools, instead of the custom cutter stuff. Or I should say, earlier, than the custom cutter stuff. I will still most definitely be doing the custom cutter tooth stuff when my O1 and W1 rods get here.

    So...my ingredients included:

    -block of nylon I had in the scrap bin..not sure exactly what nylon

    -turns out a cutter with a 78 thou radius will get within a couple though of the curvature of the teeth for these DP gears! And lo and behold. I had some weird HSS end mill that was 78 thou, and somehow had also hand ground the shank to be smaller, so it had a longer reach! WTF! First time I tried it it broke though on the deepest cut, the chip clearance wasn't so hot, and I dont have the feeds and speeds dialed in yet for a cutter that size in nylon. Luckily it was double sided so I ground the other end to be skinnier for longer and that worked.

    -The nylon had lots of burrs, I dont machine nylon very often so I just took pretty wild a%% guesses about the feedrates. I was able to clean up the gear afterwards but its dumb to have to do that. So if I end up making a bunch of these I'll do some experiments and get the feedrates and rpm perfected, and/or make it out of a different plastic. I didnt have any delrin on hand.

    -Looks like the teeth mesh great!

    -The threaded holes are for the fixture so I can flip it over and machine the other side. I mic'd the bore diamter and keyway diameters.

    -I had to file the keyways inside radiuses flat because I dont have an endmill that cuts square holes yet, cant seem to find one for sale. I guess next time I'll have to just go in deeper so the radius clears the existing geometry but I didnt want to deal with that this time.

    -I made a 32 tooth gear, because thats all I need to be able to do 27 TPI with the other gears I have. Not that I really need 27tpi but at least I can try this out with just one CNC'd gear.

    -The toolpath took about 13 minutes, totally hands off, 5 tools. But all the feed rates for the small cutters were guesses. I'm not sure how long it would take once I get it all dialed in. I'm guessing at least twice or three times faster possibly.

    -Nothing too special about the toolpath. The model was courtesy of emachineshop.coms spur gear generator in its CAD package. Exported as DXF, imported in solidworks (turn OFF constraints and merge points), then extruded, and modified to have all the Atlas Lathe geometry. No spokes on this one because its so small. All the Atlas gear measurements are pretty basic. Looks like I got it right the first time. Camworks for the toolpath. All of its 2.5 axis stuff.

    -Man the Atlas really is a pain to change gears on. I guess if I print out the gear change chart and put it near the lathe that might help. But why did they put the bracket nut on the BACK of the bracket so you have to reach around backwards and use a flashlight and struggle to get a wrench in there. Am I missing something??

    -So got it in the Atlas and started her up. Hey it works!! Not sure how it would handle a crash but for actual threading might actually do the job.







    VIDEO!!

    Hobbyist: someone who makes something sound harder than it is.
    Professional: someone who cant afford to be a hobbyist.

  • #2






    Hobbyist: someone who makes something sound harder than it is.
    Professional: someone who cant afford to be a hobbyist.

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    • #3
      VIDEO

      Hobbyist: someone who makes something sound harder than it is.
      Professional: someone who cant afford to be a hobbyist.

      Comment


      • #4
        Looks nice.
        Not sure how it would handle a crash but for actual threading might actually do the job.
        If you are lucky, it will strip. In the event of a crash, the Atlas was designed to break the bracket that supports the leadscrew at the tailstock end of the lathe.

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        • #5
          I agree with RichR. If you crashed and the only damage was to that nylon gear, you'd be fortunate.

          That was a great experiment. However, if you make the appropriate cutter, you can make a 'geared rod' of arbitrary length. Then you just slice gear blanks off with the bandsaw. It will save a lot of time if you need multiples of gears.

          Consider making more gears so you can produce 20 tpi and 13 tpi threads - those are common TPIs for 1/4" and 1/2" threads. Perhaps it would be a good bang/buck. You might also consider using Delrin.

          On my Atlas, all the bolts related to the change gears are easily accessible.
          Last edited by Tony Ennis; 10-12-2014, 08:40 AM.

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          • #6
            Doc
            bolts are standard 3/8 carriage bolts with the head modified
            George from Conyers Ga.
            Remember
            The early bird gets the worm, BUT it's the second mouse that gets the cheese.

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            • #7
              Right about now, I'd be considering making the gear from AL or 1018..... nylon is fine, so far as it goes, I suppose.

              No sense worrying about having a crash.... best to worry about how NOT to have a crash. You have enough machine sense to avoid most of the problems, I'd suppose.

              Not ALL Atlas have that breakaway bearing.
              1601

              Keep eye on ball.
              Hashim Khan

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              • #8
                Originally posted by J Tiers View Post
                Right about now, I'd be considering making the gear from AL or 1018..... nylon is fine, so far as it goes, I suppose.

                No sense worrying about having a crash.... best to worry about how NOT to have a crash. You have enough machine sense to avoid most of the problems, I'd suppose.

                Not ALL Atlas have that breakaway bearing.
                Yes mine certainly does not..the bearing looks like it could take a direct nuclear strike...

                BTW if anyone wants to try the toolpath just let me know! You need at least a 2 axis CNC (with manual quill/zaxis) and would probably have to futz around with the toolpath a bit for feeds and speeds depending on what tools and material you use. I would recommend nothing bigger than 80thou dia for the finish pass on teeth.

                Im going to try and do some threading and see how this nylon holds up. Ill probably make the other ones in delrin or some other plastic I can get cheap that would do the job, and buy the proper end mill.

                Hobbyist: someone who makes something sound harder than it is.
                Professional: someone who cant afford to be a hobbyist.

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                • #9
                  Shouldn't be any problem with it.
                  The mini - lathe series runs on 1 MOD gears [ 25.4 DP ] in moulded plastic 10mm wide
                  .

                  Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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                  • #10
                    Doc-

                    First off - Great Job! Secondly - Nylon makes mountains of burrs when machined. Trying to deburr it makes a lot of other stringy burrs. Doable, but still a pain. For Nylon, I get off all the burrs I can, then melt the remaining strings with a propane torch just close enough to melt the strings and not the project. Also, the Nylon will grow and shrink with changes in humidity.

                    Delrin and Acetal (very similar) machine very cleanly almost like a molded part when finished. Most burrs can be scraped off with a fingernail. No change in size with humidity either.

                    Bottom line is your Nylon gear will probably go forever. If not, a replacement is not far away.

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                    • #11
                      Originally posted by Toolguy View Post
                      Doc-

                      First off - Great Job! Secondly - Nylon makes mountains of burrs when machined. Trying to deburr it makes a lot of other stringy burrs. Doable, but still a pain. For Nylon, I get off all the burrs I can, then melt the remaining strings with a propane torch just close enough to melt the strings and not the project. Also, the Nylon will grow and shrink with changes in humidity.

                      Delrin and Acetal (very similar) machine very cleanly almost like a molded part when finished. Most burrs can be scraped off with a fingernail. No change in size with humidity either.

                      Bottom line is your Nylon gear will probably go forever. If not, a replacement is not far away.
                      Thanks!!!

                      BAH seriously? Ive only machined nylon a few times, its always been a mess of burrs, and never enough machining to justify dialing in the feedrates..I just assumed it was that. Okay delrin it is then. BTW I was wondering If I could burn off the "hair" last night using a lighter...do the hairs vaporize or do they make little lumps?
                      Hobbyist: someone who makes something sound harder than it is.
                      Professional: someone who cant afford to be a hobbyist.

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                      • #12
                        Some vaporize and some lumps, but the lumps break off easily.

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                        • #13
                          BTW, does anyone want a custom change gear(s) for the Atlas? I.e. some tooth number or combination of tooth numbers that doesn't exist and would result in some magical thread pitch that is otherwise impossible? Because I can now make any tooth pitch.
                          Hobbyist: someone who makes something sound harder than it is.
                          Professional: someone who cant afford to be a hobbyist.

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