ASTM specification A 48 classifies gray irons in terms of tensile strength. The usual microstructure of gray iron is a matrix of pearlite with graphite flakes dispersed throughout. Section sensitivity effects are used in the form of a wedge test in production control to judge the suitability of an iron for pouring a particular casting. Mechanical property values obtained from test bars are sometimes the only available guides to the mechanical properties of the metal in production castings. Gray iron castings are used widely in pressure applications such as cylinder blocks, manifolds, pipe and pipe fittings, compressors, and pumps. Where high impact resistance is needed, gray iron is not recommended. The machinability of most gray cast iron is superior to that of most other cast irons of equivalent hardness, as well as to that of virtually all steel. Gray iron is used widely for machine components that must resist wear.

This article discusses the types and operations of the most common machines used for die threading. The construction, types, and comparison of solid and self-opening dies are discussed. The article explains the modification of chasers for threading Monel shaft. The principal factors that influence thread quality, production rate, and cost in die threading are composition and hardness of work metal; accuracy and finish; thread size; obstacles, such as shoulders or steps; speed; lead control; and cutting fluid. The article examines these factors and describes the tools and cutting fluids used for pipe threading along with the severity of stop lines.