Abstract: A mechanical safety device for the reciprocating plunger in downwardly acting presses such as a downstroke or eccentric type, in which the plunger is connected to the piston rod of the press cylinder or to the eccentric. A stopping rod is immovably fixed on the plunger and extends vertically upwardly from the plunger and through a stopping sleeve rotatably mounted on a housing fixedly retained on the press. The rod and the sleeve have cooperating threads, the threads on the rod being divided into at least two sections and the threads on the sleeve being divided into as many sections as the threads on the rod and being spaced by arcuate surfaces. In a first rotary position of the sleeve, the threads engage with each other for stopping the plunger, and in a second rotary position of the sleeve, the threads are moved out of engagement with each other for permitting movement of the rod through the sleeve and thereby movement of the plunger.