This die is designed for cutting paper. If you want something that you can put in a press and stamp thin sheetmetal with, you will need to use a different source for the blades (actual sheet or flatstock, not just the trash from last night's chili), and you will need to set these blades in wood or metal. If it's metal, tacking them in place with your arc welder is a good idea, but you will need to run a full bead (or braze) before you apply 12 tons of force. If you are building a press die, you will also need to get a small square, to make sure you have your blades at the right angle. For just cutting paper, it's nowhere near as tough, and that's what we'll be doing today.
Don't be an idiot like me and forget to sharpen all your blades before you bend them and stick them in tight corners. I have not actually sharpened this die yet, and if/when I do, I will update this with photos. Until then, you get a verbal description of what to do. It will work.