Chapter 16: Process Capability and Tolerances

Users of steel castings establish performance requirements for specific characteristics of the castings based on the planned use. They express tolerance for variation in those characteristics to the producer of the castings. One issue which should never be taken for granted in considering capability and tolerances is the ability to measure with accuracy and precision (repeatability and reproducibility). This chapter discusses the methods for measuring accuracy and precision. It describes the variation of process characteristics, capability indices in general use, and factors related to process performance and tolerance specification.