I believe that wire EDM is the usual way to make small quantities of internal (ring) gears. It seems possible that one might imitate a mini-Fellows by moving the z-axis up/down to shave the gear. At least some high volume small ring gears are made of sintered metal. I don't know your application but have you considered commercial ring gears? Many electric drills/screwdrivers use a planetary gear train. Also, Chinese gearhead motors may be a cost-effective way to get the needed parts.
-----Original Message----- From: andy pugh <bodge...@gmail.com> Sent: March 11, 2021 5:12 AM To: Enhanced Machine Controller (EMC) <emc-users@lists.sourceforge.net> Subject: Re: [Emc-users] Gear cutting setup on low-cost HF mill?? On Thu, 11 Mar 2021 at 06:31, Chris Albertson <albertson.ch...@gmail.com> wrote: > What's the best kind of steel to buy that gives a combination of > machinability on a small mill and strength. I will concur with Marcus, when making starter gears for the Ner-a-Car I used EN8. EN8 is the old name (ie, before 1970) name for 080M40 In turn 080M40 is similar to US 1039, 1040, 1042, 1043, 1045 > Given my setup, a HF mill and manual (non-CNC) HF mini lathe which > would have the best result, a hob or an involute cutter? You can only hob if you can set the hob spindle at an angle to the gear axis. Hobbing should give a perfect profile at any tooth count, but it more difficult to arrange. You definitely can hob on a mini-mill, though. https://youtu.be/ZhICrb0Tbn4 > The really hard part that I don't know how to do is a ring gear. I can't > figure out how to cut internal teeth. Cutting internal teeth isn't something that can be done with a hob _or_ an involute cutter. You need a Fellows gear shaper, or at least to find a way to set up the equivalent on your CNC mill. https://youtu.be/72YgpVF4O7g I don't think it is impossible, with the cutting tool in the rotary axis, circularly interpolating around the blank. It might be simpler to order one wire-spark eroded for a one-off or a stock part from HPC or similar. -- atp "A motorcycle is a bicycle with a pandemonium attachment and is designed for the especial use of mechanical geniuses, daredevils and lunatics." — George Fitch, Atlanta Constitution Newspaper, 1912 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
