Cool effect, but a worthless knife. For all that work, I'd have gone to a leaf spring, as others recommended.
As far as safety goes, he's lucky he has his skin still. Kids these days.
Good skills, bad practices, and wasted effort.
Aside from the safety issues, give the kid break. He is learning a skill and making a little bit of money from it also. The knife may not be used on a daily basis and looks to be more of a ornamental / conversation piece but regardless A++ for effort.