I’ve also posted to the Vectric forum, but I thought I’d tap the talent here as well. I’m designing (yet another) wooden clock, the works to be driven by a stepper motor. I’d like to drive the works with a worm gear attached to the stepper. The problem is that, like most wooden clocks, the gear teeth to be driven are large, about .25 inches across. I’ve experimented with the VCarve threading tool path, and it looks like it should be possible given the proper thread mill. A rotary axis would be ideal, but that’s beyond me at present. I’d appreciate any advice from someone who has tried something like this, and maybe a hint as to a source of (large) thread mills.
I’ve not tried what your trying to do, but i can not see how it can be done without a rotary axis. I doubt the “cavities” in the threads can be reached using a flip jig, 2-sided milling. Now, i have watched 4-sided milling on youtube (winston moy) i cant wrap my head around that . Winston uses F360.
It may be possible to mill a worm gear using the external thread toolpath in VCarve, but it’d be cheaper to do it with a rotary axis and a v-bit. The problem that you’ll run into is that large thread mills are extraordinarily expensive…buying a rotary axis would be cheaper than the thread mill you would need. All of the larger mills I’ve come across have also had shank sizes too large for an ER20 collet.
Two- or 4-sided milling wouldn’t work, since you need to be able to mill directly over the center of rotation of the worm to not mess up the shape of the helix.
It’s fairly easy to model one in Vectric’s software, but I can’t think of a practical way to mill without a rotary axis.
Thanks for the advice! A user on the Vectric forum suggested using a keyhole bit with the threading path, and sent me a sample .crv. I’m going to experiment more with that, but it looks like the necessary gear diameter might be too large. I could drive the clock with a regular spur gear, but using the worm gear would allow for a thinner clock case and a higher “cool” factor. I’m going to look into the idea of a rotary drive because, as Dan pointed out, of the rather breath-taking costs of large thread mills.
So, this may or may not be a terrible/dangerous idea, but I’ve found myself wondering whether or not a finger joint bit could be used as an external thread mill for wood. I generally wouldn’t use Chinese bits, but this one looks like it may have finger spacing that could work for gears…
Could possibly also use something like one of these wedge router bits:
There’s also a store on Etsy that sells wooden gears, including worm gears and wheels, if you’re not set on making them yourself.