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The wide assortment of metals and alloys used for structural purposes in the aerospace industry is classified in terms of machinability. Applications of these materials to important aerospace components, as well as major machining operations on these components, are indicated. The preponderance of metal removal is accomplished by conventional machining methods. Recommended cutting conditions for milling, turning, and drilling of important alloys are presented. Electronic machining methods are applicable to special operations. A summary of these is presented, which includes applications, surface finish, dimensional tolerance capability and practical rates of metal removal.

Cost data are presented which provide justification for making systematic studies of all types of machining processes in order to select the most applicable tool materials. Full tool life tests are suggested for obtaining reliable machining data. Specific tool life test data are supplied for the drilling, reaming, and tapping of 4340 steel at 42 Rc, for the face milling of 32510 and 60003 grades of malleable iron, and for the comparative evaluation of T-15, and ultrahard high speed steels, C-8, titanium carbide base, and ceramic cutting tools. Sources of machining information are referenced along with a description of the Air Force Machinability Data Center.

THE AIR FORCE has set up a program to evaluate the machining characteristics of the more commonly used high-strength thermal-resistant materials. This paper describes the test results to date. Four materials are being tested: SAE 4340 quenched and tempered to 50–55 Rockwell C, SAE designation H11 quenched and tempered to 50–55 Rockwell C, AM-350 solution treated and aged, and A-286 solution treated and aged. Machining tests include: turning milling, drilling, and tapping.*