Abstract: This invention relates to a clutch device for a transmission wheel and a transmission shaft. Two brake rings surround a hub axle and are contained in a brake hub. The first brake ring is intermediate the hub axle and the second brake ring and arranged so that, due to a time differential of braking by an external force on the two brake rings, a bevel canal in the first brake ring braces against a loose pin inserted in the hub axle, forcing the loose pin to part from the transmission wheel. This achieves the purpose of separating the transmission wheel and the transmission shaft in order to instantly stop the work done by the transmission shaft, and is particularly effective with common machine tools. It may be used with a magnetic solenoid or a manual trigger control, pre-regulating the bolts for the slackness and tightness of brake linings, to successive action with a proper time differential.