Answer
When the handle hits the board and stops suddenly, Newton's first law says that the steel head will continue to move for a short distance, resisting changes in velocity, until the force of friction between the head and the handle has brought it to rest. It will have then moved down some to where the handle is a little wider, resulting in a tightening of the head onto the handle.
Work Step by Step
When the handle hits the board and stops suddenly, Newton's first law says that the steel head will continue to move for a short distance, resisting changes in velocity, until the force of friction between the head and the handle has brought it to rest. It will have then moved down some to where the handle is a little wider, resulting in a tightening of the head onto the handle.