[DampRobot]

I have to put a plug in here for hand G-Coding. (It's how they did it in the good old days!) If you don't want to buy/learn a CAM package, and the part isn't too complex, you really can hand program the mill.

Each mill is different, but here's the gist of it: each program starts out with a series of commands (part of a header) that get the mill ready to cut. Sets the zero, which mode the mill is in, etc. Then, before each cutting sequence, you tell the tool to spin at a certain rate, such as S1500 (in RPM) and the direction (CW or CCW) with the correct M command. The feed rate (usually in inches per minute) is then set with the F command, F2.5 for example. On some mills, you need to set the tool zero using a H command (H01, for example would import the Z-zero for the first tool).

After the setting up, it's just a matter of controlling the toolpath with G00 and G01 commands. G00 followed by an x, y, or z coordinate (or a combination of the three) moves the mill to that location at the maximum mill speed. G01 moves the tool in a straight line from the last coordinate to the one given in a straight line at the feed rate. G02 and G03 are used for cutting in circles, but its a little to late for me to get into that...

Heres some psuedo-G-code for drilling a hole and returning to the origin:

G00 X0.5 Y2.375 Z3.0
G00 Z0.5
G01 Z-0.75
G01 Z.5
G00 Z3.
G00 X0. Y0.

You get the idea.

This is just an extremely quick primer on G-code, if you want to do it for real, search around for your mill model and the exact G and M codes it uses. Or, you know, you can always just get a CAM program and learn to use it.