3D Printable Through Bolt Hammer
Contained here are parts to print a hammer, with a through bolt used as the striking surface and weight.
The code is clearly commented with variables at the top to change sizing, I had made mine with a 9/16"x5" bolt and nut I had on hand which is what the design as posted is sized for.
See here for more: https://www.appropedia.org/Improved_Hammer