316 FORMS OF ENERGY Milling machines which remove metal by means of rotating cutters, planing machines which remove metal by moving an object backward and forward under a stationary cutting-tool, turning machines which remove metal by applying a cutting-tool to an object while in rotation, grinding machines, and power drills are the parents of printing presses, tanks, automobiles, and airplanes. f Fig. 107. Idealistic view of a 15-arm Owens bottle blowing machine. (Courtesy of the Owens-Illinois Glass Company.) The machine-tool industry resembles research in that it employs relatively few, but highly trained, men. The total number of employees in the machine-tool industry in the. United States in 1940 was 83,000. The machine tool makes possible mass production, but it, like research, cannot be produced by mass-production methods. The improvement in the design and materials used in machine tools renders older tools obsolete in about seven years. One of the problems of modern industry is that of retooling every few years. The introduction of new tools generally involves changes in factory buildings, rerouting materials in assembly lines, changes in methods of handling, etc., to such an extent that retooling is not economically feasible until the older tools have paid for themselves. Progress in production methods is therefore closely geared to the useful life of machine tools. A single machine tool may cost as much as $150,000, and for that reason it cannot be replaced very often.
MACHINES HAVE RAISED LIVING-STANDARDS 317 Automatic Machines Are Gradually Replacing Semi-automatic Machines. Most of the machines in present-day factories require people to tend them. Machine-tenders have to do the same thing day after day, at the pace which the machine sets. Such work is not creative, and such Fig. 108. Automatic automobile frame plant. Capacity of automatic plant, 8000 finished and painted frames per day. (Courtesy of the A. 0. Smith Corporation.) workers are really slaves to the machines which they tend. An important development in industry is the introduction of automatic machines, which require no human labor other than that involved in producing, adjusting, and repairing them. Modern nail-making machines keep up their incessant clatter without the presence of an attendant. Modern automatic bottle machines can turn out 250,000 bottles a day. Modern automatic die-casting machines can turn out castings at the rate of 4,204,800 per machine per year. Automatic punch presses help to make Woolworth stores possible. Electrical devices, to be studied later, such as solenoids, thermostats, meters, magnetic valves, transformers, electromagnets, vacuum tubes, and the electric eye have made possible automatic machines that could