[quote=sanddrag]I bet Joe Johnson could explain better than I. It uses really thin wire that gets really hot and it cuts intricate shapes in metal. Look for "wire EDM" on google. I found this that tells a little more
http://www.emachineshop.com/machines/fabrication/kerfing/wire-edm.htm[/QUOTE]
yes, I meant Wire EDM when I said "wire burn"
EDM stands for Electro Discharge Machining. Essentially, you use a very good conductor (carbon, copper, etc.) as a "tool" and you pass a spark from the tool to the work piece. The spark vaporizes a bit of the work piece (as well as a smaller bit of the tool). This allows for very detailed parts to be made (almost all tools for complex molded parts use some EDMed features in the tool). In the case of wire EDM, you have a copper wire that "burns" its way through the metal. The tool is constantly made new by moving new wire between the upper and lower wire guides. Wire EDM is perfect for flat parts like gears -- it is even better if you have several gears to make as many plates can be bolted together allowing one pass to make N gears.
We typically pay about $50 for a custom gear made from 1/4 inch steel plates. If you don't have a wire EDM source in your neck of the woods, I can put you in touch with some sources in the Detroit area that will take MasterCard and will give you a good price for FIRST projects.
One big advantage of EDM by the way is that it does not care if the work piece is hard or soft. Also, the parts themselves get warm but not so hat that the heat treatment of the base metal is affected -- so hard parts stay hard.
This year, the only thing we used our EDM source for is to put accurate holes in the hardened pinions we used in our Dewalt transmission (yes, I know I owe folks a whitepaper on that topic -- it will come, be patient). The source we used charged us $20 per pinion to put very accurate holes into the hardened pinions we bought from Dewalt so that we could press these pinions on the Fisher Price and Globe motors. We felt that $20 was not too bad for what it saved us.
Joe J.
P.S. most sources like to have an IGES file with the gear profile you want cut rather than saying "a 10 DP gear with 100 Teeth" Again, this should not be a road block if you don't have access to CAD, but things usually go smoother if you can give them an IGES file.