OM154-26-1/4” Omega Piloted Aircraft Countersink Cutter, 7/16” x 100 x 1/4”. OMEGA Piloted Aircraft Microstop Countersink Cutters are used to make precision countersinks to accept flush-head fasteners. OMEGA Piloted Aircraft Microstop Countersink Cutters feature a 5/8” body diameter, high speed steel, 100°, 1/4-28 thread. OMEGA Piloted Aircraft Microstop Countersink Cutters are designed to be used for countersinking holes for 3/16” or smaller diameter fasteners. The flush fasteners head diameter must not exceed 7/16” to guarantee proper seating of the screw. OMEGA Countersink Cutters are precision ground to exact tolerances to insure concentricity. OMEGA Countersink Cutters can be used in any microstop cage that accepts 1/4-28 threaded shank cutters.