detent elements 24 embodied as recesses and extending in the direction of the tool holder 54 of a detent mechanism 20 of the synchronizing device 18 fig1 and 5 the detent elements 24 embodied as recesses have a domelike cross sectional area to achieve gentle engagement the transitions in the circumferential direction to the recesses are rounded in the region of the conical face 28 fig5 the first coupling element 32 protrudes with its end remote from the tool holder 54 into a second corresponding coupling element 44 which furthermore forms one part of the drive bearing 74 of the beater mechanism 14 in the second coupling element 44 detent elements 22 of the detent mechanism 20 that are embodied as balls are supported in a plurality of radially extending bores distributed over the circumference in an idling position of the drill and or chipping hammer the detent elements 22 embodied as balls protrude radially inward with one part past an inner circumference of the second coupling element 44 and in the process are braced radially inward each on a respective formed on collar in the bores the detent elements 22 embodied as balls form a root inner circle 36 which has the same diameter as a root inner circle 34 of the detent elements 24 embodied as recesses fig1 u2013 4 moreover the number of balls matches the number of recesses so that the first and.