One method is to make a multi-tooth straight hob with teeth that have flat sides. On each pass it does a full cut on the tooth or gullet on the center line of the gear and partial cuts to the teeth and gullets above and below. That makes a faceted approximation of involute teeth. If you have the patience and calculate things right you can make the teeth smoother by raising or lowering the hob and changing the gear rotation to hit the high spots between the first pass cuts. Or just buy the one cutter from a set of eight 0.5 MOD cutters and cut one tooth at a time to the full smooth profile. Each cutter is made for a specific range of numbers of teeth. IIRC they provide the best fit near the middle of their ranges.
Or you could build your own gear hobbing machine. https://www.collegeengineering.co.uk/product-category/castings/gear-hobbing-machine/ On Wednesday, March 10, 2021, 11:31:35 PM MST, Chris Albertson <albertson.ch...@gmail.com> wrote: I'm looking for advice on gear cutting. I've got a low-end harbor freight mill with a 4th axis added (actually a rotary table) and I want to cut some module 0.5 spur gears. I know that the smaller the gear the more precision is required. These need to be as strong as possible too. They need to survive impact loads. What's the best kind of steel to buy that gives a combination of machinability on a small mill and strength. I'll buy either a set of involute cutters or a commercially made hob in 0.5 size. 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? 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. I might just buy these if they can't be machined. If this works I need about 60 total gears plus all the ones I used for testing Yes I can 3D print these but plastic would not be strong enough. _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
