An overload protector is secured to a robot arm and a tool to protect the tool from being overloaded or forced into an abnormal position. A rocker assembly is located within the cavity in the protector and the cavity is pressurized in order to force a wall of the rocker assembly into a sealing relat-ionship with a wall of the cavity. The rocker assembly has a peripheral wall in which a number of semi-conical recesses are formed. A like number of semi-conical detents are formed in the wall of the cavity. The detents are accommodated in the recesses when the rocker as-sembly is in a sealing relationship with the cavity wall. When the tool is overloaded or forced into an abnormal position the rocker assembly rocks in the cavity with result-ing leakage of fluid from the cavity and a drop of pressure. A pressure switch detects that drop and signals the robot to stop.
