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ω=WtvtKnowing how the power splits enables the determination of the transmitted load at each mesh.(a)Form milling cutter(b) Spur gear shaper cutter(c) Hob for small pitch gears having large teeth(d) Hob for high pitch gears having small teethFIGURE 9–4 A variety of gear cutting tools (Gleason Cutting Tools Corporation, Loves Park, IL)
CHAPTER NINESpur Gear Design 325(a)Gear being shaped with shaping cutterFIGURE 9–5 Gear shaping operation and shaping machine (Bourn & Koch, Inc., Rockford, IL USA)(b)Gear shaping machineof the next adjacent space. This method is used mostly for large gears, and great care is required to achieve accurate results.Shaping[Figures 9–4(b) and 9–5] is a process in which the cutter reciprocates, usually on a vertical spindle. The shaping cutter rotates as it reciprocates and is fed into the gear blank. Thus, the involute-tooth form is generated grad-ually. This process is frequently used for internal gears.Hobbing[Figures 9–4(c) and (d) and 9–6] is a process similar to milling except that the workpiece (the gear blank) and the cutter (the hob) rotate in a coordinated fashion. Here also, the tooth form is generated gradually as the hob is fed into the blank.The gear teeth are finished to greater precision after form milling, shaping, or hobbing by the processes of grinding, shaving, and honing. Being products of sec-ondary processes, they are expensive and should be used only where the operation requires high accuracy in the tooth form and spacing. Figure 9–7 shows a gear grinding machine.(b)Large hobbing machine(a) Long pinion and a hob in a hobbing machinePinionHobFIGURE 9–6 Gear hobbing operation and hobbing machine (Bourn & Koch, Inc., Rockford, IL USA)