Abstract: A clamp for joining hollow tubular members in end-to-end abutting relationship has two stiff elements shaped in correspondence to opposed inner wall surface of the end cavities of the tubular members and is provided with both elastic shims and a threaded screw for urging mutual separation between the elements. One of the elements has two truncated right circular cylindrical pegs projecting from its surface for entering corresponding holes in the walls of the tubular members. The threaded screw has a conical tip that enters a conical concavity in the opposite element to lock the elements against relative longitudinal movement when expanded within the tubular members.