What does cogging mean?
Cogging has two distinct modern lives. As an engineering term, it describes the unwanted torque fluctuation that arises in permanent-magnet electric motors when the rotor's magnets interact with the slots of the stator; the result is a slight jerkiness, most noticeable at low speeds, which designers minimize through skewed magnets, slotless windings, or careful pole shaping. In metalworking, cogging denotes the initial stage of forging or hot-rolling, in which a cast ingot or billet is worked down to a more manageable size in a cogging mill. The word derives ultimately from 'cog', the tooth on a gear wheel, whose further etymology is obscure but likely Scandinavian in origin. An older, now obsolete sense survives in historical accounts of gambling, where 'cogging' meant cheating, particularly with loaded or manipulated dice. Today the term is almost entirely technical, familiar mainly to motor designers and metallurgists rather than general readers.
Torque ripple in an electric motor caused by magnetic interaction between rotor and stator slots.
"Careful magnet skewing reduced the cogging to imperceptible levels."
The preliminary reduction of an ingot or billet by rolling or forging in a cogging mill.
"The steel was shaped in the cogging mill before finishing passes."
(Archaic) Cheating or fraud, especially at dice.
"He was caught cogging the dice and barred from the tavern."
That faint stutter you feel when an electric motor starts turning? Engineers have a name for it: cogging.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of cogging
Cogging derives from 'cog', meaning a tooth on a gear wheel, a noun recorded in English from the Middle Ages whose deeper origin is uncertain but often linked to Scandinavian sources such as Norwegian 'kugg'. From this mechanical noun came the verbal sense of fitting or providing with cogs, and hence the gerund 'cogging'. Separately, an unrelated or obscurely related verb 'to cog' meaning to cheat produced the archaic gambling sense of cogging, attested by the sixteenth and seventeenth centuries.
How cogging is actually used
Today 'cogging' is chiefly a technical term in electrical engineering and steel manufacture; the older gambling sense ('cogging the dice') is obsolete and found mainly in historical texts. In technical writing it appears almost exclusively in fixed phrases such as 'cogging torque'.
Easily confused with cogging
Clogging means blocking or a type of dance; cogging refers to gear teeth, motor torque ripple, metal-rolling, or (archaic) cheating.