Heat treating is often used to carburize metal parts such

Chapter 12, Problem 14E

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Heat treating is often used to carburize metal parts such as gears.  The thickness of the carburized layer is considered a crucial feature of the gear and contributes to the overall reliability of the part. Because of the critical nature of this feature, two different lab tests are performed on each furnace load. One test is run on a sample pin that accompanies each load. The other test is a destructive test that cross-sections an actual part.  This test involves running a carbon analysis on the surface of both the gear pitch (top of the gear tooth) and the gear root (between the gear teeth).  Table E12-6 shows the results of the pitch carbon analysis test for 32 parts.