a sealing assembly is clampable to the end of a threaded male pipe section . the assembly includes an aperture which guides a drill bit radially inwards to establish a radial blind bore in the outer surface of the pipe section into the threads thereof . a cylinder is slidably positionable over the aperture and carries an elongate strip of resilient sealing material slidably disposed in a transverse slot therethrough and a slidable cylindrical punch shaft coaxially aligned with the cylinder . radially inward movement of the shaft punches out a cylindrical sealing plug from the strip . the plug is forced by continued inward movement of the shaft along a cylindrical aperture in the cylinder which receives the shaft and is in coaxial alignment therewith until the plug is press - fit into the radial blind bore . upon make up of a pipe joint comprising the male section having the thus installed plug and a female section , the internal threads of the female section cut through the outer surface of the sealing plug thereby effecting a fluid - tight seal between the threads of the respective sections , thereby preventing helical fluid leakage in the space formed between the mating threads of each section .