👉 In mechanical engineering, a "countershaft" is a type of gear mechanism that uses a single shaft to transmit motion from one part of an engine or machine to another. The counterclockwise direction of rotation of the shaft corresponds with the desired direction of movement for the motion it transmits. This type of gear arrangement can be used in applications such as power transmission, servomotors, and reciprocating pumps. In summary, a countershaft is a single shaft that is used