Stigma (letter) Stigma (letter) Stigma (ϛ) is a ligature of the Greek letters sigma (Σ) and tau (Τ), which was used in writing Greek between the Middle Ages and the 19th century. It is also used as a numeral symbol for the number 6. In this unrelated function, it is a continuation of the old letter digamma (originally Ϝ, cursive form ), which had served as a numeral since antiquity and was conflated with the σ-τ ligature in the minuscule handwriting of the Middle Ages. The στ ligature (, ) was one of many ligature forms that came into widespread use as
Electric torque wrench Electric torque wrench An electric torque wrench is a planetary torque multiplier or a "gearbox" mated to a brushless electric motor. At the end of the "gearbox" is a reaction device that is used to absorb the torque. This allows the operator of the tool to use the electric torque wrench with very little effort. These tools are primarily used anywhere accurate torque is required on a nut and bolt, or where a stubborn nut needs to be removed. These planetary torque multiplier gearboxes have multiplication ratios up to 4000:1. The correct torque output is adjusted by controlling the voltage.