I'm a computer geek who hangs around the machine shop too much and I wrote a small program in response to our need for creating gcode for milling sprockets. In order to visually confirm the results from the desktop I also made it generate a CAD file (dxf). Anyway, I thought it was too neat / useful not to share so I've posted it on my website at http://www.idleamusements.com/sprocketeer.htm. You basically choose the standard chain size ( or enter a custom pitch and roller diameter) and the number of teeth and it generates the gcode and CAD file.
Download it and give it a spin. If you find any problems or have any suggestions for improvement please let me know via the email address on the page.
I've created an installation package which should include all of the files that you'll need. It is now available for download at http://www.idleamusements.com/sprocketeer.htm . If you have any problems or have any suggestions let me know.
I also wouldn't mind some pictures of the final result for my webpage if you find this little program handy.
Mike, I successfully downloaded and installed the program. Pretty neat. The computer at school where our shop is had some trouble installing the program, but I had no problem at home. I'm going to take the g code file to the school tomorrow and see if I can't cut a sprocket.
I've been wanting to cut sprockets for about 5 years now. I even made a servo driven gear/sprocket hobbing attachment for our manual mill this year. This should be a lot faster and easier!
I ran your program and generated code for a 18 tooth 35 pitch sprocket. We haven't actually cut it yet, but I loaded it into our Tormach Mill stuck a pen in it and it traced the outline of the sprocket. We will probably cut the sprocket this weekend when I get the coolant pump going. One thing I noticed is that the tooth profile is a bit taller and sharper than an ansi standard sprocket. I don't think this is a problem, but it is a bit different.
I left the teeth as pointed as they could be. It seems that the final point cut of the sprocket teeth is something of a personal preference so I left it up to the machinist to make that final cut. Basically add a final circle event with a center of 0,0 and the diameter of your desired final profile.
If anyone can find a good standard or rule of thumb for that final trim then I'll make it cut that path from the start, or add that final event at the end.