Breaking a stud or a bolt is a pretty common shop catastrophe, but one for which a fair number of solutions exist. Drill it out, shoot in an extractor, or if you’re lucky, clamp on some Vise-Grips and hope for the best. But when a drill bit breaks off flush in a hole, there aren’t a lot of options, especially for a small bit. If the stars align, though, you may follow this video guide to dissolve the drill bit and save the part.
Looks like [Adam Prince] lucked out with his broken bit, which he was using to drill the hole for a pin in a small custom brass hinge. It turns out that a hot solution of alum (ammonium aluminum sulfate), which is available in the spice rack of your local supermarket, will dissolve the steel drill bit without reacting with the brass. Aluminum is said to be resistant to the alum as well, but if your busted bit is buried in steel, you’re out of luck with this shop tip.
We’re a bit disappointed that [Adam]’s video ends somewhat abruptly and before showing us the end result. But a little Googling around reveals that this chemical technique is fairly well-known among a group that would frequently break bits in brass – clockmakers. It remains to be seen how well it would work for larger drill bits, but the clocksmiths seem to have had success with their tiny drills and broaches.
As for the non-dissolved remains of the broken bit, why not try your hand at knife making?