High speed steel (HSS) cutters are the least-expensive and shortest-lived cutters. Cobalt-bearing high speed steels generally can be run 10% faster than regular high speed steel. Cemented carbide tools are more expensive than steel, but last longer, and can be run much faster, so prove more economical in the long run. HSS tools are perfectly adequate for many applications. The progression from regular HSS to cobalt HSS to carbide could be viewed as very good, even better, and the best. Using high speed spindles may preclude use of HSS entirely.