Torque Wrench

A torque wrench is a tool used to apply a specific, controlled amount of torque to a fastener such as a nut, bolt or lag screw, typically built as a socket wrench fitted with either an indicating scale or an internal mechanism that signals, often with a click or a small movement, when a preset torque value has been reached. The tool matters wherever a fastener's tightness is critical to the safety or performance of an assembly, letting the user apply consistent, precise tension rather than guessing by feel. John H. Sharp of Chicago filed the first torque wrench patent in 1931, for an indicating type he called a torque measuring wrench; in 1935 Conrad Bahr and George Pfefferle patented an adjustable ratcheting torque wrench with audible feedback and a mechanism restricting back-ratcheting once the desired torque was reached. The beam-type torque wrench was developed in the late 1920s and early 1930s by Walter Percy Chrysler for the Chrysler Corporation with the Micromatic Hone company, and Paul Allen Sturtevant patented his own beam-type design in 1938, becoming the first person to sell torque wrenches commercially; a dual-signal deflecting beam design followed in 1948 from the Australian company Warren and Brown.