Abstract: Disclosed is an improved spring brake assembly, and a method for making same, which is particularly resistant to unauthorized disassembly and its consequent hazards. A diaphragm is locked between two opposing portions of a housing. The two opposing portions of the housing are both made of steel and are welded rather than clamped to one another. The weld is performed in such a way that the diaphragm is not burnt or otherwise damaged by the welding process. The opposing portions are configured as a cylindrical coupling between a male member having an inwardly extending lip, and a female member preferably having an inner circumferential ledge, which cooperate to trap the periphery of the diaphragm at an end of the coupling remote from the weld.