I left out an important part.

While he claims to have done it on himself, he is something of a maso-macho-tough-guy, the only time I saw him do it he did it on, to, a helper. While the kid was still in shock, holding his mashed thumb. This guy grabs the kids thumb, forces it down on a low bench, steps on his hand and in one smooth motion puts the knife he keeps in his nail bag over the nail and drives it on through with one good tap from his framer.

He pulls out his bandanna, roughly wraps it up the thumb and tells the kid to get back to work. Wasn't all that traumatic simply because it was over and done with in a few seconds while the kid was unaware of what he was doing and still in shock.

In comparison gently drilling the thumbnail with the fine tip of an exacto blade is IMHO the least traumatic and damaging method I know about. Which is why I use it. The swift, brute-force approach has the advantage of seeming 'manly' and it gives the boys something to talk about over beer. Even more so if you do your own thumb. I'm not sure how I work both the hammer and knife with only one hand free but given some determination I think I could manage it. Not that I would want to.

I did see this guy put a sixteen penny nail through his foot with a pneumatic nailer. He pulled it out with the Vice-Grips he had in his bag and went back to work. You could tell it hurt and he limped for a time. We mentioned it at lunch and he shrugged it off. Tough old coot.