So, I was on reddit talking about my favorite hammer and someone asked how I attached the new handle. I figured I might as well show some pics of it. It's basically a wedged mortise and tenon. I didn't even use glue. It hasn't budged even though I wail on stuff with it on a regular basis.
Here's the original handle for comparison.
This is a little 4 ounce hammer that I bought for $1.50 at my local Daiso. Daiso is like a Japanese dollar store where everything is a buck fifty. I changed out the dinky little handle for a fat piece of iron bamboo. It now hits like a 16 ounce carpenter's hammer with a fraction of the effort. I learned that just changing the handle has a dramatic effect on performance.