What is the recommended hardness of a pinion for helical or herringbone gear teeth to sustain life, measured in BHN?

The recommended hardness for a pinion in helical or herringbone gears is typically measured in Brinell hardness number (BHN) and falls within the range of around 48-65. This hardness level is crucial for ensuring that the pinion exhibits the necessary wear resistance and fatigue strength to sustain operational life under varying loads and conditions.

For this type of gearing, the hardness of the pinion affects its ability to withstand the contact stresses that arise during operation. A higher hardness can lead to better performance by minimizing wear and reducing the likelihood of surface fatigue, which can significantly extend the life of the gear system.

The specified hardness range also considers the characteristics of the materials used and the heat treatment processes that can modify their mechanical properties. This is particularly important for helical and herringbone gears, which are designed to handle significant torque and require a balance between hardness and ductility to accommodate operational demands without fracture.

Thus, the desirable hardness range for pinions operating in these gear types focuses on strength, wear resistance, and the ability to effectively transfer loads within the designed application, making the range of 48-65 BHN appropriate for achieving a long service life.