Patent ID: 8890449

Claim:
An electric power tool comprising: a motor that rotationally drives a tool element; an operation input receiving device that receives an operation input to operate a rotation speed of the motor from an operator of the electric power tool; a rotation speed control device that controls the rotation speed of the motor in accordance with the operation input inputted through the operation input receiving device; a counter that performs a counting operation to count, as a count value, an elapsed time required for the motor to rotate by a predetermined amount; a reset device that resets the count value of the counter to an initial value when the motor rotates by the predetermined amount; a reference time changing device that changes a reference time, which is used as a determination criterion to determine whether or not a lock state of the motor has occurred, in accordance with the operation input inputted through the operation input receiving device; a lock state determination device that determines that the lock state has occurred when the count value of the counter has reached the reference time; and an invalidation device that performs, in a case where a false determination of occurrence of the lock state is caused due to the operation input inputted through the operation input receiving device, at least one of a first invalidation operation to invalidate the lock state determination device and a second invalidation operation to invalidate continuation of the counting operation by the counter.