I came across these tools which haven’t been called for in quite a while, but when the opportunity arises they are really handy. I learned this technique from Dan Nauman at a BAM meeting several years ago. When I got home I made my own tools. Three were made from coil spring and one was an Allen wrench as I recall.
The pattern I tested came from Dan’s demonstration. The printed copy is glued to the sheet metal with rubber cement. I had an ash log just the right height for working - about vise top height. As soon as the tools were made I tried them out.
I have forgotten the gauge of sheet I experimented with but I think it was 16 gauge and the holes punched easily and cleanly with the slugs sinking into the end-grain surface. I thought it was a lot faster and more fun than drilling if there were a lot of holes to make.
The shape of the cutting edge of the punches is important as well as their sharpness. I don’t know the upper limit of metal thickness for this technique but I’g going to guess that above 14 gauge it would be better to go to a mechanical punch or to drill.
See Dan’s work here: