Abstract: The present invention relates to a mechanical seal for a shaft, having a rotary seal ring and a stationary seal ring which slide on and come in contact with each other for sealing a fluid. A blade-like sealing end portion formed at one seal ring is resiliently pressed, through a coil spring or a flat leaf spring, to a flat sealing end surface formed at the other seal ring. The blade-like sealing end portion is symmetrical at the inner and outer peripheral surfaces thereof with respect to the edge surface thereof, and the angles formed by the inner and outer peripheral surfaces of the sealing end portion with respect to the edge surface thereof are set to 90.degree. or more, and preferably in the range from 105.degree. to 150.degree.. This facilitates the machining of the sealing end portion and prevents the sealing end portion from being broken, thus assuring a stable sealing performance for a long period of time.

Abstract: A mechanical seal wherein a smooth sealing end surface is formed at one end of a rotation seal ring and a stationary seal ring, while a sharp edge-like sealing end portion in slidable contact with the smooth sealing end surface is formed at the other of seal rings, the sealing end portion having a width of 0.1 to 0.3 mm, and the spring face pressure to be imparted to that portion of sealing end portion which slidably contacts with the sealing end surface is set to a relatively high value from 30 to 50 kg/cm.sup.2. Materials of which the sealing end surface and the sealing end portion are made are selected from hard ceramics.