Beam type:

Beam type torque wrench. The indicator bar remains straight while the main shaft bends proportionally to the force applied at the handle.The simplest form of torque wrench consists of a long lever arm between the handle and the wrench head, made of a material which will bend elastically a little under the applied torque. A second smaller bar carrying an indicator is connected back from the head in parallel to the lever arm. This second arm is under no strain at all, and remains straight. A calibrated scale is fitted to the handle, and the bending of the main lever causes the scale to move under the indicator. When the desired indicated torque is reached, the operator stops applying force. This type of wrench is simple, inherently accurate, and inexpensive.

This torque wrench as it is known today was a development in the late 1920s/early 1930’s by Walter Percy Chrysler for the Chrysler Corporation and a company known as Micromatic Hone. The Cedar Rapids Engineering Company's sales representative Paul Allen Sturtevant, licensed by Chrysler to manufacture his invention, patented the torque wrench in 1938. Sturtevant became the first individual to sell torque wrenches to the trade.

Close up of beam type torque wrench showing detail of the torque display scale. This shows a torque of about 160 inch pounds or 17 newton metres.A more sophisticated beam type has a dial gauge indicator on its body, which can be preset to a value so that a visible and/or electrical indication is given when the preset torque is reached.