I have a half dozen old hammers of different types with damaged or broken handles. Like the vise restoration I did last time, I had zero experience replacing hammer handles and was a little nervous about ruining a cool old hammer. After watching some videos and reading through a few excellent instructables, I decided to tackle my grandfather's old ball peen hammer. Before you begin, you will need a replacement handle, wedge set and some sealant (all are described in the following steps).
Step 1: Disassemble the Hammer
Using a vise or clamp on the handle, carefully cut off the hammer head. Place the head on a support which will allow you to knock the wood handle cutoff down and out of the hammer head eye (the hole in the hammer head that the handle is driven into). I used an old blunt punch to drive it out. Keep the driven out piece to help with shaping the replacement handle. I also kept the old handle, which I am going to reshape and reuse for a smaller hammer.
Step 2: Clean Up the Old Hammer Head
I used a wire brush on an angle grinder to remove years of rust and buildup. This is an important step, so that you can see if the hammer head has any hidden defects (deep cracks, etc.) which would cause concern. I used some sandpaper wrapped around a wooden dowel to clean out the eye. Some people might wish to smooth out all of the old marks or even polish the hammer face, but I am planning on using this hammer, so they stayed.
Step 3: Select or Make Your Handle and Install
There are some superb videos online for making hammer handles if that is the route you want to go. I would suggest watching videos from Jimmy DiResta or Brent Bailey Forge. Both are amazing makers and excellent at giving you invaluable tips.
You can also buy some quality handles online or from the local hardware store. There are a couple things to know about hammer handles if you chose to buy them.
First, you'll need to find a handle roughly the same length as the hammer originally had. Make sure and measure the entire length of the handle, including the part that goes into the eye.
Second, you'll need to pick the right type of handle shape for the hammer's eye. There are two basic shapes: square (usually used for for claw hammers) and oval (for mallets, sledges, etc.).
Third, you'll need a wooden and metal wedge that are the appropriate size for the handle and hammer head eye opening (i.e. the wooden wedge needs to be wide enough to fill the entire length of the slot cut into the wooden handle). Most online or store hammer handles come with a sized handle and wedge set. Check this before you buy. Cost for the handle and wedges range from $4 to $9. If you decide to make your own handle or your purchased handle does not come with a wedge set, you can buy a set of those as well. Wooden wedges come in different sizes, as do metal wedges, but metal wedges also come in flat or circle shape. Flat wedges are driven in perpendicularly to the wooden wedge, while circular metal wedges are driven in the middle of the eye.
Using the piece of the old wood you removed from inside the hammer head eye, mark up the new wood handle with a pencil for a close approximation of the wood you need to remove for a tight fit. Go slow. Remove a little at a time, checking hammer head fit frequently. As my old barber used to say, "I can always take more off, but I can't put it back on." I used a rasp, but others I've watched used a draw knife, spoke shave or band saw. You want a snug fit. Make sure the hammer head sits squarely on the handle with the wood coming all the way through the eye.
Although you don't have to, this is a good time to sand off the thick clear coat that comes on the purchased wooden handles.
Now you are ready to drive the wooden wedge into the handle slot. With the hammer head snuggly on and while holding the hammer handle in your hand (not resting against a bench), drive the wooden wedge into the slot until it will go no further. Turn the hammer 180 degrees between hits. If you try doing this step with the handle on a solid surface, the wooden wedge will likely break. Next, do the same with the metal wedge. Perpendicular to the wooden wedge if metal wedge is flat. In the middle of the eye, if the metal wedge is circular.
Either cut off or grind off any extra wood and wedge material sticking out of the top of the eye and apply Wonderlokking glue to the wood in the eye to swell it and seal it.
Step 4: Paint & Clear Coat Hammer
Prepare to finish the handle by taping the hammer head off. Stain the wooden handle as desired. Allow to dry for 24 hours. I used clear coat per directions on can, but some prefer wood finish/protection oil.
Completely unnecessary step: I wiped the hammer head off with acitone and taped off the sides and faces. I used Rustoleum Verde Green Hammered Spray Paint for an old school look.
Enjoy your new hammer.