Original poster: "Gerry Reynolds" <gerryreynolds-at-earthlink-dot-net> Hi All, So far in this thread, I've heard of four types of drill bits: 1. High speed steel 2. Carbide 3. Titanium Nitride 4. Colbalt Could someone rank these as to hardness and cost and comment on application. Also, are there other bits to consider (not counting wood applications)? Gerry R