In these examples,'S'denotes structural rather than engineering steel; 275 or 355 denotes the yield strength in newtons per square millimetre or the equivalent megapascals; J2 or K2 denotes the materials toughness by reference to Charpy impact test values; and the'W'denotes quenched and tempered steel ('Q'or'QL'); and thermomechanically rolled steel ('M'or'ML').
42.
The term " Hotchkiss gun " also refers to the "'Hotchkiss Revolving Cannon "', a Gatling-type revolving barrel machine gun invented in 1872 by Benjamin B . Hotchkiss ( 1826 1885 ), founder of Hotchkiss et Cie . It was a built-up, rifled, rapid-fire gun of oil-tempered steel, having a rectangular breechblock which moved in a mortise cut completely through the jacket.
43.
A cold chisel is a tool made of tempered steel used for cutting'cold'metals, meaning that they are not used in conjunction with heating torches, forges, etc . Cold chisels are used to remove waste metal when a very smooth finish is not required or when the work cannot be done easily with other tools, such as a hacksaw, file, bench shears or power tools.
