How do you tighten the handle on a hammer?

You first make sure the socket in the head is clear and smooth. Fit your shaft into this socket and bang the other end on a firm surface, -the head will settle into position, but now needs to be pounded on with a soft face or dead blow hammer. When the end of the shaft is level with end of head you have it in position. Now you pound a small metal wedge into the end of the shaft to spread it. These wedges are available in all hardware stores in packs of 3-4 quite cheaply.