Electrode wear

I've pretty much gleaned the fundamentals of EDM of books pretty solid, but needless to say I lack the practical experience. Can any of you guys give me some sort of idea of electrode wear rates in off-hand-glance layman's terms, preferably from an older-machine point of view ie Charmilles D1S/D10/D20? Just a few examples, like "Well, x type of graphite starts to lose it's sharpness after burn number y at a sink-depth of z." and etc. like that. I'm thinking about getting a sinker EDM soon, and I want the general idea of how many parts I can burn with the same electrode (I'm guessing not very many) before it starts to show appreciable wear, like .010 wear being "appreciable" for my application. Thanks EDM dudes!

General G

Figure about 30% wear on the electrode for general work. If you burn 1"deep the first trode will get you about .7 deep the next trode will get about 70% of whats left and the 3rd trode will get whats left. If you need real good definition you should hit it with a 4th trode. If you move from cav. to cav. and use up the trodes you can get by with about 8 trodes to burn 11 cavities.

If you are considering doing production machining on a sinker edm, you should look at using tungston copper. It is fairly expensive, and difficut to machine. However, the wear rate is a fraction of carbon or telco copper.

I don't know about difficult to machine. But it is pretty expensive. We used to buy out of the scrap box at EDM Supply. They make custom electrodes as well as supplying EDM stuff. They always seem to have cutoffs at a reduced price.