Abstract: An adjusting mechanism for a hammer drill that will switch the drill from conventional drill only mode to a hammer drill mode by rotating an adjusting rod. The generally cylindrical adjusting rod includes an impact cam and an adjacent and smaller drill cam. One of the two cams will be in a position adjacent a thrust ball, which is on the back of the spindle. When the drill cam is rotated into position to contact the thrust ball, a clutch face on an output gear will be held in spaced relation to a clutch face on an impact bushing with a resulting drill only rotational motion of the spindle; when the impact cam is rotated into position adjacent the thrust ball, the two clutch faces will come into engagement with one another and create a hammer drill motion of the spindle.