You have to adjust your mind to the concept that when you hammer on sheet metal with a steel hammer onto a steel dolly or anvil that you will expand or increase the surface area by thinning the metal.
Cold forming sheet metal with a hammer.
Something like a sharpie to mark on the sheet metal.
A ball peen hammer.
This is a handy metal fabrication technique you need to learn.
You may want a smaller hammer for small shapes or a larger hammer for larger shapes.
How can you go about shaping metal with hand tools alone.
Something to cut the metal like sheet metal shears or tin snips.
The tokyo based goldsmith yutaka nagai demonstrates how to hammer down a gold ingot to form a sheet.
You also have to grasp the fact that you can reduce the area of sheet metal by thickening it.
For this example we will hammer form some tank end caps.
Follow along as i demonstrate how you can begin shaping metal with hand tools only.