Abstract: An improved closure assembly for plastic drums is provided which includes female buttress threads formed on a tubular projection of the drum head, and an adaptor inserted into the tubular projection threadably engaging the buttress threads, the adaptor having internal standard pipe threads adapted to receive standard pipe threaded members, like dispensing valves, pump fittings, as well as standard bung plugs. Means are also provided for sealingly isolating the buttress thread inter-engagement to prevent product accumulation therebetween and means are also provided for locking engagement of the adaptor and the tubular projection on the drum.

Abstract: A threaded bunghole structure for plastic containers is disclosed which requires no gaskets, has a warp-free sealing surface, and is leakproof. In one embodiment, the structure is formed by insert blowmolding over a female-threaded metal flange such that the outermost plastic-to-metal interface border is disposed inwardly from the sealing surface. In a second embodiment, an annular metal insert is disposed between plastic blowmolded threads and a sealing surface.