Abstract: An air-operated hammer is provided for removing risers or gates from castings. The hammer includes a piston having a rod to which an impact member is releasably latched. Operation of the piston is controlled by a pneumatic logic control circuit, the operation of which is initiated by simultaneously depressing a pair of thumb-operated pneumatic switches. When actuated, the control circuit acts to cause the piston to retract to cause the impact member to compress one or more blow-delivery springs, with the latch being automatically released, upon desired loading being achieved, to permit the release of the stored energy in the springs resulting in the impact member being impelled against a gate or riser to be broken off. Meanwhile, the circuit operates to reverse the direction of movement of the piston so that it extends to be automatically once again latched to the impact member.