the extra control afforded by the design of these bits was especially helpful. It takes a tough bit to drill through hard ...

And heat dulls bits quickly. In general, it’s a good idea to drill through metal using as slow a speed as possible using a ...

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 ... for larger drill bits, but the ...

A smith may dunk a freshly forged sword into a bucket of oil or water to make the metal harder, or a craftsman with a drill bit ... than untreated steel, therefore the bits last much longer.