Abstract: A collapsible plunger (10) for use in a pump is disclosed having a load carrying cylinder (12) forming in inwardly facing tapered end (14), a plug (16) forming an outwardly facing taper (18) mating the inwardly facing tapered end of the cylinder, a stud bolt (20) engaging plug 16 on one end, a plunger clamp end (22) abutting the cylinder on the opposite end and a nut (24) engaging the other end of the stud bolt. The nut is free to move away from the plunger clamp end so that the stud bolt is never in compression. The tapered end of the cylinder will yield to the plug at a predetermined force. The abutment surfaces (30 and 32) of the cylinder and plunger clamp end permit some relative movement between the two.