Cartridge center punch. By The Metalist. 4:46 video:
https://www.youtube.com/watch?v=DW2BTKn1BJ8
Previously:
https://www.homemadetools.net/forum/...143#post180364
Metal Brake Build Guide
https://www.homemadetools.net/forum/...462#post177691
https://www.homemadetools.net/forum/...981#post175933
https://www.homemadetools.net/forum/...743#post170866