Yes, it has to be a 6mm keyway. I don't have enough funds to be buying a broach and the shims, though I could easily make the 20mm bushing.
Same story with cutting the teeth. No funds to get a small flat back chuck to be able to put it on my horizontal/vertical rotary table and buy a 1.75 module x 20º gear cutter.
I got two guys on the PM site to quote me for hobbing the teeth. One said $100, the other $70 for the 70T gear, and I might also want to make blanks for the 30 and 35 tooth gears that the machine needs for other pitches. If I get just the 70T gear, I can do 0.25, 0.5, 1.0, 1.25, 1.5, 2.0, 2.5, 3.0 and 5.0. Adding the other two, I would be able to also do 0.75, 1.75, 3.5, 4.0 and a few others. Oddly, none of the gear combinations allows doing 0.7, though I don't know if I'd ever have to do an M4x0.7. A thread that small could be done with the dies I have.
Of course, as you mentioned in our text exchanges tonight, once I have the YAM CNC lathe up & running I won't need any gears at all! I think is just a good idea to have them for this lathe in the event I should ever sell it off. They would help with the value.
Same story with cutting the teeth. No funds to get a small flat back chuck to be able to put it on my horizontal/vertical rotary table and buy a 1.75 module x 20º gear cutter.
I got two guys on the PM site to quote me for hobbing the teeth. One said $100, the other $70 for the 70T gear, and I might also want to make blanks for the 30 and 35 tooth gears that the machine needs for other pitches. If I get just the 70T gear, I can do 0.25, 0.5, 1.0, 1.25, 1.5, 2.0, 2.5, 3.0 and 5.0. Adding the other two, I would be able to also do 0.75, 1.75, 3.5, 4.0 and a few others. Oddly, none of the gear combinations allows doing 0.7, though I don't know if I'd ever have to do an M4x0.7. A thread that small could be done with the dies I have.
Of course, as you mentioned in our text exchanges tonight, once I have the YAM CNC lathe up & running I won't need any gears at all! I think is just a good idea to have them for this lathe in the event I should ever sell it off. They would help with the value.