Abstract: A universal interface unit is provided for use with a pneumatic drill having an axially extendable tool holder, the interface unit being adaptable for use with `valve in head` type and `thru head` type pneumatic drills of different sizes. The interface unit includes a compact housing which fastens to the pneumatic drill and houses one or more proximity sensors for sensing the position of extendable tool holder and also houses valves for controlling air flow to the extend and retract ports of the drill. The proximity sensors sense the position of the extendable tool holder and send signals to a remote controller. The valves receives signals from the remote controller and communicate with the drill extend and retract ports to control the tool holder position. The valves are plumbed to be easily convertible for use with either the `valve in head` type of `thru head` type pneumatic drills by removing two plugs and changing a fitting.