A fastener placing tool (11) for placing fasteners of the breakstem blind rivet type incorporates a force/stroke monitoring device (22) which comprises an assembly body (24) detachably mounted on the tool between the latter and the anvil (18), a load-cell sensor (33) carried by the assembly body (24) for sensing the force applied by the hydraulic piston (16) to the jaw assembly 17 with respect to the anvil (18), and a non-contact stroke-sensor (35) carried by the assembly body (24) for sensing the position of the jaw assembly (17) relative to the anvil (18). The stroke-sensor (35) operates without physical contact with the jaw assembly (17) or any part of the tool moving therewith. To this end the jaw assembly (17) is connected to the hydraulic piston (16) by means of an adaptor tube (23) which has a conical tapering outer surface. The clearance distance between the sensor (35) and the adjacent part of the conical surface of the adaptor tube 23 varies with the axial position of the adaptor (23) and jaw assembly (17).