MACHINABILITY OF MATERIALS

The machining characteristics were determined for a variety of ultra high strength steels, titanium alloys, nickel base alloys and cobalt base alloys of current production interest to the Air Force. This group of alloys was the result of a field survey intended to select the most difficult to machine materials presently being fabricated in aerospace components. Most of the conventional machining operations on these alloys can be performed with reasonable tool life, providing that specific machining conditions are followed. This report presents recommendations for particular machining operations. It should be noted, however, that even small departures from suggested variables, such as cutting speed, feed, cutting fluid, as well as tool material and geometry, may result in a significant reduction in tool life. High speed edge milling tests were also run on a select group of materials. This particular operation is becoming increasingly important in airframe fabrication. In addition, residual stress and distortion studies were run on four high strength structural alloys. The data developed give an indication of the large variations possible in surface integrity as a function of machining conditions employed.