abrasive metals like stainless steel or cast iron, spend a couple of bucks more for black oxide or a cobalt steel drill bit for metal. These bits will bore more holes before becoming dull.

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 ...

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 ...