Bimetal saw blades are named after the fact that they contain 2 distinctly different types of metal - a carbon steel back and a much harder tooth edge. The tooth edge is generally made out of M42 Cobalt steel and designed to cut harder materials such as steel. Bimetal saw blades will generally last 3-4 times longer when cutting metals than standard flexback saw blades. Remember to use proper metal cutting fluid or compound when cutting metals. Contact us at any time for blade recommendations.