Moly drill bits work well with mild steel. Cobalt bits are expensive and best choice for the abuse common in farm shops, but…drill bits by definition are “consumable items.” The differences ...

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.

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 ...