Laser machining system with x, y and z axis translational movement and C and D axis rotational movement of a beam positioning device to perform automatic tracking over the surface of a workpiece at a constant distance utilizing a sampled capacitive sensing device operative in the refractory interval between laser pulses. The system also automatically determines the normal vector to the part surface and is controllable along a selectable axis for accurate tracking the focal point of the beam across the surface of the workpiece even when the beam is oriented at an angle other than normal to the surface of the workpiece. The system also provides for control of the of the focal point of the beam at a particular displacement from the machining nozzle tip, using a least means squares curve fitting technique and further provides for identification of a mounting fixture unique to a workpiece by sensing coding on the surface of the fixture thereby to select a particular part machining program.