Sledge hammers are large and heavy tools that are more susceptible to wear and wood splintering than the average household hammer. When a sledge hammer shows signs of wear or the handle seems loose, the tool can be dangerous to use. If the hammer head doesn't show signs of damage, the handle can easily be replaced to restore the tool's functionality.
Remove the old handle by cutting it away with a hacksaw.
Put the hammer head in a vice for stability. Use a punch and drill to remove the remaining handle inside the eye of the hammer head.
Insert the new handle as far as possible into the eye of the hammer head. Trim any excess wood that sticks out of the top of the hammer head.
Open the wedge slots in the top of the new handle with a chisel and insert wood wedges. Tap the wedges into place with a hammer.
Saw away any excess wood so the new handle is flush with the top of the hammer head.
Insert metal wedges across the wood wedges and drive them in until flush.