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 ...

So it’s always a joy to pick up a new trick, especially one as simple as putting a hardened edge on mild steel using a drill bit as a filler rod. This tip comes to us by way of [Jody], aka ...

whereas cobalt is typically used for harder materials like cast iron or stainless steel. Tungsten-carbide tipped (TCT) and titanium nitride coated (TiN) drill bits are also popular. HSS is hard ...