1520 plotter (was RE: Your VIC-20 is worth $300!!! W@W!)

You'd really only make a mold like that if you intended to produce many, due to the expense. And that would be if your mold was at least a three part, with the mold cavity having a through hole, to be capped off on each end by other components of the mold. If you preferred a blind ( not through ) hole cavity, you would probably burn the teeth into it ( after boring out most of the material first ) with a conventional electrode type EDM machine, which might also be a whole lot easier to home brew than a wire type. But then you generally have to machine the electrodes. Easier to do because you would be machining the teeth on it's OD, but machining graphite is a messy, nasty task, and you still need a cutter, though a hand ground fly cutter might do ( milling saw type better ). Other very realistic possibility is ... For an alternate to thread wires, use the shank portion of drill bits. Between all the fractional, wire gage, and letter sizes, there are an awful lot to choose from. You often are able to find something within a thou or so, if not tenths. For info on measuring gears etc, check Machinery's Handbook put out by the Industrial Press. It is the machinist's and mechanical designer's bible. For Tony, having a lathe. If you had a plate, turned circular to indicate it in when you set it up, with the same number of holes as teeth on the gear, drilled in a evenly spaced circular bolt pattern on the face of the plate, bolted to the lathe chuck, and a fixed portion bolted to the bed ( or ways, or headstock, etc. ) with a pin that would locate into the holes in the plate, it could serve as a dividing head for use on the lathe. Then hand grind a slotter type cutting tool to the shape of the valley between the gear teeth, mount it in the tool post, and by moving the carriage up and down the ways, cut that shape into a blank a little shave at a time, dialing the next depth of cut on the cross slide, just like on a slotter ( or shaper ). Tony Duell wrote: