IP 166 : 77(R1992)

The loads which can be transmitted by a pair of gears under given operating conditions are different for different lubricants, i.e., the lubricants have different load-carrying capacities. If the load-carrying capacity of a lubricant is exceeded it fails to protect the gears and the surfaces of the gear teeth become damaged. Some of the forms of damage which can occur are described in Appendix A1. In the IAE gear machine, which is used to determine the relative load-carrying capacity of lubricants, the most common form of damage is scuffing, although scoring is also experienced. As the incidence of both of these types of failure is affected by the lubricant they are used as criteria of performance in the test described in this method.