Nails are stupidly easy to make compared to a large sheet of metal. I wouldn't call most guillotine head separators, "blades." The sharpness doesn't matter, as long as the thing weighs enough, it will slice through. The diagonal matters more than the sharpness. Heating up that much metal and laminating/ heat welding it into a solid piece takes a fuckton of work, and half a fuckton of coal.
I can make you a nail in 4 hits of a hammer, and I'm not a good smith. I know masters that can do it in 3 hits.
