1/4th in bolt centerer

Ive been trying to make a hotend out of 1/4th bolt to practice with drilling out bolts before spending a bit of money for the metric ones, but if youve ever tried doing that without professional tools like a metal lathe and stuff, it seems almost impossible to do. expecially when all you have to work with is just a hand drill.

So I made this, you put a 626zz bearing in it, and use two nuts on the end of the bolt so it gets a decent grip to the inside of the hex part, so it doesnt wobble or go slanted slightly and mess the thing up. Just find a drill bit that will fit in the center of the bearing, and drill slowly for a few secs at most, no real pressure on it and it'll create a little cone in the center of the bolt dead center if you have everything leveled right.

Ive used it a few times now, and 9/10 times, I get dead center cone, which makes it really easy to drill through with decent accuracy with a hand drill.