A crank has a connection portion with a connection recess defined therein which has an engaging recess, a reception recess and a reception groove. The engaging recess is located at a closed end of the connection recess and the reception recess is located at an opened end of the connection recess. The reception groove is located between the engaging recess and the reception recess. An axle has an engaging portion at an end thereof and the engaging portion is engaged with the engaging recess. A guide surface is defined in an outer periphery of the cylindrical body. A ring-shaped washer is mounted to the cylindrical body and securely fills into the reception groove and the gap between the axle and the reception recess.