There is a limit to the amount of work that a tool can do. Before the invention of High Speed Steel, metal cutting was done at a snail's pace. HSS revolutionized the machine shop.
When you purchase a drill bit from the local hardware store, it is probably made from carbon steel or High Speed Steel (HSS). Carbon steel can form a sharp edge and can be made hard. It is suitable for low speed usage such as files, chisels, hand plane blades. Or the occasional drilling that is done around the house. Cutting should be done slowly to prevent overheating the tool.
Carbon steel lacks strength at high temperatures, and for many cutting operations high temperatures are produced. High Speed steel (HSS) can withstand higher temperatures and maintain its hardness so it can cut faster. HSS is tougher than carbide and ceramic materials and less likely to chip during cutting operations. HSS can form sharper cutting edges than carbide cutters. Finer surface finishes are obtained.
Better quality HSS cutting tools will have a coating of TiN (Titanium Nitride) for added hardness and lubricity. TiN prevents sticking and galling and reduces friction which means less heat and faster cutting.
As good as they are, HSS drill bits are far inferior to Cobalt drill bits. Shown on the picture to the left are two HSS drill bits and two Cobalt drill bits. Notice that the HSS has a black oxide coating covering the typical shiny steel surface. Cobalt has a slight copper coloring to the steel.
Personally, I buy nothing but Cobalt drill bits. The price of a Cobalt drill bit is far less than the cost of the part that I'm drilling a hole into. Better quality holes and longer life makes cobalt the professional choice.
