THE CNC SHIELD HAS NOW BEEN DEPRECIATED AND REPLACED WITH THE GRBL BREAKOUT
The Arduino CNC Shield makes it easy to get your CNC projects up and running in a few hours. It uses open source firmware on Arduino to control 4 stepper motors using 4 A4988 Stepper drivers, with this shield and the Arduino you can build all kinds of robotics or CNC projects including CNC routers, laser cutters and even pick & place machines.
GRBL 0.8c compatible. (Open source firmware that runs on an Arduino UNO that turns G-code commands into stepper signals (https://github.com/grbl/grbl)
4-Axis support (X, Y, Z , A-Can duplicate X,Y,Z or do a full 4th axis with custom firmware using pins D12 and D13)
2 x End stops for each axis (6 in total)
Spindle, Coolant enable and direction
Uses removable Pololu A4988 compatible stepper drivers. (A4988, DRV8825 and others)
Jumpers to set the Micro-Stepping for the stepper drivers. (Some drivers like the DRV8825 can do up to 1/32 micro-stepping )
Stepper Motors can be connected with 4 pin molex connectors.
Setup Instructions: http://blog.protoneer.co.nz/arduino-cnc-shield/