This document provides methodology for designing reliability into mechanical components. It discusses testing wear-related parts for 2 times their expected cycle life to ensure no failures occur during operational use. It also describes using a probabilistic design method called stress/strength interference to design non-wear parts subjected to reversing loads, selecting a safety margin probability number based on the mean and standard deviation of material strength and stress functions. All components should be designed to have a reliability better than a target for the total operational use time.