Determination of Z_X acc. to

The size factor Z_X takes into account

• The statistical size influence (due to the distribution of weak points in the structure)
• The theoretical strength size influence (caused by smaller stress gradients at larger dimensions)
• The technological size influence (due to the forging ratio, unevenness of the structure, etc.)

Factors influencing Z_X are:

• Material, material charge (degree of purity), forging
• Heat treatment, hardness depth and distribution
• Radius of curvature of the flank
• Module (support of the core)

Z_X must be determined individually for the pinion and gearFor more information, see DIN 3990 part 2