Hammer Drill

A hammer drill comprises a motor including an output shaft, a shaft assembly rotationally engaged therewith, a hollow spindle, and a hammer mechanism comprising a piston arranged for reciprocating motion within the spindle. The shaft assembly comprises a first part carrying a first gear engaged with a gear on the spindle to cause spindle rotation, a second part carrying a crank member to cause piston reciprocation, and a connecting part configured to rotationally interconnect, or disconnect, the first and second parts. In a first position of the connecting part only one of the first and second parts is rotationally engaged with the output shaft to enable rotation of only one of the first gear and the crank member respectively, while in a second position both the first and second parts are rotationally engaged with the output shaft to enable rotation of both the first gear and the crank member.