Page 68 - Gear Technology Solutions

reduction at the drive axle. The advantage of this concept is the lower torque in
the complex shift or automatic transmission and the high torque only at the ring
gear at the drive axle.

Figure 17: Hypoid gearset location in vehicles with rear wheel drive

4.9 Is Lapping an Attempt to make Hypoid Gears Conjugate?

Lapping like grinding is a hard finishing process. In grinding the same profile
and length crowning applied in the soft cutting process is created. Grinding re-
establishes the original surface function after the heat treatment. In lapping
material is only removed in the tooth contact area. This not only establishes a
good rolling condition, it also makes the flank surfaces more conjugate in the
area where the tooth contact patterns are located.

Lapping and grinding are hard-finishing operations. The soft manufactured
bevel and hypoid gearsets have to be heat-treated, which in the most common
case begins with a case carburizing of standard gear steels steel such as AISI
8620 or 16MnCr5. In order to give the low carbon steel a surface hardness in
the 60 HRc range, a layer of carbon enrichment below the surface of 0.8 to

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