Rod-type synthetic resin insulator with overcoat and metal fittings

A synthetic resin insulator comprising a fiber-reinforced plastic rod, metal fittings which hold both ends of the fiber-reinforced plastic rod, and a seamless unitary overcoat which consists of an elastic insulating material, covers the total surface of the fiber-reinforced plastic rod located between the metal fittings and is provided at its outside with a plurality of sheds, said metal fittings having metal sleeves gastightly fixed thereto and being operative to receive both ends of the overcoat, both ends of said overcoat being sandwiched between the metal sleeve and the fiber-reinforced plastic rod and fixed and sealed in the metal sleeve by pressing the sleeve in the radial direction so as to isolate gastightly the interface between the overcoat and the fiber-reinforced plastic rod from the external atmosphere, and wherein the elongation of the outer surface of the overcoat resulting from assembly with said fiber-reinforced plastic rod and pressing of said sleeves is not higher than 2%.