A pipe coupling clamp including a pair of clamp half members essentially C-shaped in cross-section each having a pipe flange receiving groove for receiving the mating flanges of two pipes to be coupled. The clamp half members being hinged together at one pair of ends by a hinge including plates and releasably connected together at the other pair of ends by a locking eyebolt and associated locking eyebolt nut hingedly connected at its proximal end to the end of one clamp half member to allow pivoting moving through a slot into an open securing jaw on the other end. The locking eyebolt includes, at its proximal end, an eyebolt seating portion connected to a stepped threaded portion of reduced diameter at its distal end. Thus, initially, on loosening of the nut, the locking eyebolt will not disengage from within the securing jaw.