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|Gear honing is a finishing process that can be applied to external and internal spur or helical gears of up to 180" dia.|
|Honing can improve the sound quality of shaved, hardened gears by removing nicks and burrs. Also, the process can improve Involute, lead, tooth spacing pitch diameter run out and surface finish, Figure 1. Typically, shaved gears have a tooth surface finish ranging from 25 to 40 micro inch, while honed gears are in the 8 to 14 micro inch range. Honing will always improve the characteristics of shaved, hardened gears. Honing can also be used to prolong the wear life and increase the load-carrying capacity of hardened ground gears by improving surface finish to a point where up to 80 percent surface contact can be achieved. An example of this application is in the aerospace industry, where gears operate at high speeds under heavy loads. The gears are usually cut, heat-treated and ground (16 to 32 micro inch) to provide highly accurate tooth surfaces. However, tests with exotic profile-meters reveal that the ground surfaces have jagged, wavy profiles which will support heavy loads or provide long wear life only if costly break-in procedures are carried out. Employing honing on a 39-tooth,5 -diametrical-pitch2,0 -degree-pitch-ang7le.8, 00' pitch-diameter spur helicopter drive gear reduced surface finish to 8 micro inch, increased wear life by 1000 percent and increased load carrying capacity by 30 percent.|
|Honing tools are usually throwaway types that are discarded at the end of their useful life. They are abrasive impregnated tools in the form of a helical gear. The honing tool teeth are thinned as the tool wears. This tooth thickness reduction can continue until the hone O D causes root or fillet interference with the work gear. Then the honing tool OD must be reduced by a dressing tool. It is not unusual for a tool to hone from 5000 to 8000 pinion gears in a production operation. Eventually, the thinning of the hone teeth results in interference at the root of the hone teeth with the work gear OD, at which time the hone is considered to have ended its Useful life. In some cases the hone root can be re-cut (gummed-out) with a grinding wheel in the tool room to provide additional life. Selecting proper honing tools depends on the tooth finishing method, the gear material and the honing operation requirements.|