A hand-held pneumatically-powered breakstem rivet placing tool comprises a pulling head (12) driven by a pneumatic piston and cylinder device (13). The drive is transmitted by means of a chain (15), one end (45) of which is secured to the body (11) of the tool and the other end (49) of which is secured to the piston rod (35) of the pneumatic device. Between its two ends the chain forms a loop which passes over a roller (52) which is connected to the pulling head (12) by means of a link mechanism (54, 58). When the pneumatic device (13) is actuated, the movable end (49) of the chain is pulled down, thus pulling the roller (52) and driving the head (12) to place a rivet. The roller (52) is carried on the top of a plunger (56) which is continuously urged upwards by air pressure in the cylinder (63) in which it slides, thereby to return the mechanism to its original position after a rivet has been placed.