Using an Edge Finder
Before doing precise work on a milling machine, one must locate the edges of a part accurately. An edgefinder is
designed to do this on edges with flat vertical surfaces. An edgefinder is composed of two concentric cylinders, spring
loaded together. To use it you must first insert it into the machine with the appropriate collet. The big end of the
edgefinder is held in the collet at least ½ way in. Start the spindle and set the speed to approximately 1,000rpm. Flick
the bottom of the edgefinder to induce a wobble in the smaller diameter. The smaller diameter is usually .200”
diameter. Then, move the part into the tool very slowly. The edge finder will center up, then break out of concentricity
suddenly. At that point, reset the dial indicator or digital readout for that axis of the machine to a value equal the radius
of the edgefinder. Repeat the process at least twice to make sure your edge finding was correct.