Gear Production

MAR 2015

Gear Production

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10—GEAR Production Supplement F E A T U R E alloy steel with a hardness of 28-32 HRc, a tooth depth of 0.438 inch and length of 7.25 inches, and 80 teeth in total. Using a carbide 2 start hob, the total cutting time was eight hours. With a TGII abrasive wheel, total grind and dress time came to four hours. By using a systems approach— which takes the abrasive, the work material, the machine and process conditions into account— the research concluded that grinding is a cost-effective alternative to hobbing and shaping, producing removal rates of 7 cubic inches per minute per inch. Mr. Plainte says that job shops, large gear makers, maintenance and repair facilities, gearbox rebuilders, and producers of specialty gears should consider grinding for a variety of reasons. These include lower cost, fewer setups, competitive cycle times, reduced tooling inventory and the ability to respond quickly to customers' needs. "No matter what type of operation it is, though, there are certain things that an operator L&H Industrial, call 480-968-6141 or visit Norton Saint-Gobain Abrasives, call 254-918-2313 or visit must keep in mind in addition to choosing the right grinding wheel, such as proper coolant application, keeping the wheel face clean with scrubber nozzles and using a quality oil coolant," Mr. Plainte says. "And of course, you need a machine that's both stiff and powerful, but that's certainly not a problem with the grinder that L&H has chosen. It's a monster." Strategic Streamlining The beauty of that beast is becoming more apparent over time, according to Mr. Tagle. To date, L&H has used the Höfer to grind more than a dozen gears complete from blanks. He has learned plenty along the way. One lesson involves the difference between rough and fnish grinding. "You need to dress the wheel more often when you're rough grinding," he says. "By doing that, you hold a better tooth form, because the wheel's surface can become distorted due to wear and material buildup." Another has to do with heat treating. When grinding a gear complete from a blank, heat treat occurs between the roughing and fnishing processes. During the roughing phase, the operator must determine how much stock to leave in place, depending on whether the gear An aftermarket replacement gear for mining applications is shown in L&H's new 23,916-square-foot addition, which will house the welding shop and new offce space.

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