In a printer, a printing clutch and a hammer impact changeover mechanism are controlled through a control member by one electromagnet, in such a manner that in response to a printing signal the clutch is engaged through the control member by the electromagnet to start one printing cycle and, in the second half of the printing cycle, the electromagnet is operated to enable a hammer impact change-over mechanism with the aid of the control member. The energizing forces of two weak spring members are applied to a cam follower member operatively coupled to the printing hammer so that when a printing type element having a large printing surface is selected, the energizing forces of the two spring members are utilized to allow the printing hammer to strike the type element strongly, and when a type element having a small printing surface is selected, the energizing force of only one of the two spring member is utilized to allow the printing hammer to strike the type element less strongly.