This is a great idea to make a wooden hammer that would be very effective in combat. It has a sturdy head, a sharp back for a stab attack, and spikes on both ends of the handle.
Step 1: Materials
You will need gorilla tape, a half inch thick wooden dowel(length to your liking), a wooden shim(found a home depot), and any multi-tool that has a saw and a knife.
Step 2: Carve the Dowel
this step is pretty easy if you have any experience with carving. Just sharpen both ends of the dowel to a point. There should be three types of dowel: birch, hardwood, and oak. I used birch, but for extra strength use hardwood. Oak is stronger but it is really hard to find one of the right thickness.
Step 3: Shaping the Head
Now you will need to shape the hammer head from a wooden shim. Shims are soft and easy to carve but if attached correctly they can really take a beating and do some serious damage. The head should be about 6 inches long with a sharp point on the skinny side and the hammer head as the thicker side.
Step 4: Attaching the Head
This is what it all comes down to. If attached correctly the hammer head will be super durable and strong. You should use thin strips of gorilla tape in a criss-cross method that wraps around diagonally.