fig3 a in the upper right section of the drawing engages the guide plate 8 and adjacent to the cam 21 there remains a free space of several mm e g of 4 mm due to the selection of the pivot angle of the slide 9 of 2 7 u00b0 a stop lug 22 of the actuation member 17 can therefore slide through this space when the actuation member 17 is released and pivots about its pivot axis 18 into the off position under the action of a compression spring not shown instead of a hinge formed by the groove 10 and the projection 11 the guide plate 8 and the slide 9 can also be formed as flexible parts e g so that a small pivotal movement of the slide 9 in opposite directions which is necessary to provide a displacement path for the cam 21 is insured the cam 21 can also be formed so that it possesses some flexibility by selecting an appropriate material and or by its resilient connection with the slide 9 thereby in each case the cam 21 can extend without any problems into the operational region of the stop lug 22 on the other hand during the chiseling operation see.