Portable electric grinder

摘要

A portable electric grinder wherein the grinding wheel is held against rotation relative to the spindle by two annular clamping rings. The spindle has a motor-driven hollow outer shaft and an inner shaft which is installed in the outer shaft and can be held against rotation with the outer shaft by a manually depressible arresting member. One of the clamping rings rotates with the hollow shaft and the other clamping ring mates with the inner shaft. When the inner shaft is held against rotation and the motor is started for a short interval of time, the hollow shaft rotates the one clamping ring which rotates the grinding wheel and the other clamping ring by friction so that the grip of the clamping rings upon the grinding wheel is loosened and the grinding wheel can be fully separated from the spindle by completing the unscrewing of the other clamping ring from the inner shaft. The motor drives the hollow shaft through the medium of a step-down transmission.