I do some small scale metal working for model cars and I made this hammer to shape thin sheet aluminum.
The head was made from a piece of 3/4" diameter nylon with a 3/8-16 tapped hole and the handle is a piece of aluminum rod turned down and threaded to match.
I did a bit of freehand profiling just to add some interest to the ends of the head.
In the background you can see an aluminum "wheel tub" I made. It still needs some finishing but the shape is there.