Abstract: An improved flywheel for an electromechanical tool such as a nailer or stapler. The tool is provided with a blade-like driver which is frictionally moved through a working stroke by an electrically driven flywheel, the driver being squeezed between the flywheel and a support element such as a counterrotating flywheel, a low inertia roller, or the like. The flywheel has a peripheral working surface with parallel edges. The working surface of the flywheel makes a line contact with the driver during the driving stroke. The flywheel is provided with at least one groove formed in and extending along its working surface. Throughout its length the groove is angularly related to the parallel edges of the flywheel working surface so that the groove traverses the line contact between the driver and the flywheel during each working stroke. This more efficiently prevents build-up of foreign material on the driver and flywheel and produces less and more uniform wear of the driver and flywheel.