There's a spreadsheet "gearcutterstemplateupdateddec292012.xls" in the downloads area, excellent piece of work, for making cutters by the "two buttons" method, although I'm not sure it does all gear types - take a look?
I have a copy of one that I downloaded *somewhere*, can't remember where, though! There's still the need to make multiple cutters for different DP and tooth counts, and although the tooth profile isn't an exact involute making a geartooth-count specific cutter will probably be closer than a bought cutter at the extremes of its range...
The usual two-disc method of cutter making is fairly easy to extend from single to four tooth (making cutting quicker and a little kinder to the machine) by offsetting the cutter blank equal amounts in the direction of each jaw of the 4-jaw chuck and gashing the cutting edges at the resulting "corners" - this gives a 4-tooth form-relieved cutter that's relatively easy to sharpen and retains the correct form too...
With a stretch of the imagination I can see this extended to higher tooth counts, but it would be a piece of work to produce a home-made 12 or 16 tooth cutter...
Single-tooth cutters usually need to be set on an eccentric arbor, but do a good job of cutting fairly accurate gears, albeit a bit slowly
Dave H. (the other one)