474 Modern Metalworking Copyright Goodheart-Willcox Co., Inc. Boring Boring, Figure 26-83, permits holes of any diameter to be 3 machined accurately with fine surface finishes. On the vertical mill, a single-point tool is fitted to the boring head, which is then mounted in the spindle. The hole diameter is controlled by offsetting the tool point from center. The adjustment screw is graduated for direct reading. 26.9 Industrial Applications Many types of milling machines are in use in indus- try. They range in size from small tabletop models to machines capable of handling work weighing many tons, but they operate on the same basic principles as those used in training programs. Most industrial mill- ing machines have CNC capability and automatic tool changers, Figure 26-84. Some CNC machines can handle speeds of 25,000 rpm or higher and feed rates of 600 inches per minute. This type of milling, frequently used in the aerospace industry, is known as high-velocity machining. It involves using machining practices such g g as high feeds and speeds, rapid traverse movements, quick acceleration and deceleration rates, and fast tool changes. CNC machines must be built with a base, drive train, and coolant system capable of meeting these operating conditions. Balanced cutting tools, toolholders, and CAD/CAM systems that can create toolpaths for this type of work are also needed. 26.10 Milling Safety Practices Safety precautions are very important and must always be practiced in the machining of metals. Safety practices cannot be overemphasized in metalworking applications. To minimize hazards, observe the fol- lowing precautions when performing milling opera- tions and handling milling equipment. The following procedures are suggested for the safe operation of a milling machine: • Do not attempt to operate the milling machine until you know the proper procedures and have been checked out on its safe operation by your instructor. • Never attempt to operate any machine tool while your senses are impaired by medication or other substances. • Wear approved safety glasses. • Dress appropriately. Wear closed-toe shoes. Remove any tie, sweater, or jacket. • Confine (tie up or tuck in) long hair and loose clothing. Keep them away from the moving parts. Marposs Corp./Komet of America, Inc. Figure 26-83. A boring head with a programmable electronic controller interfaced with the machine’s computer numerical control (CNC). It relates measurement data to present tolerance limits, and signals the tool to make size adjustments to compensate for tool wear. Communication to, and powering of, the tool is entirely wireless. Photo courtesy of Grizzly Industrial, Inc. www.grizzly.com Figure 26-84. A 3-axis CNC vertical milling machine with an automatic tool changer. Automatic tool changer