IRWIN 373412BX 4-1/2-Inch Bi-Metal Hole Saw
The IRWIN 373412BX 4-1/2" Bi-Metal Hole Saw is crafted from the highest quality bi-metal.  The teeth are attached to a carbon steel body by a process called electron beam welding.  The result is a tool composed of two types of metal welded edge-to-edge - also know as bi-metal construction.  Because the IRWIN Hole Saws are engineered and manufactured for exceptional sharpness and durability, they will cut much more than wood.  These saws will also cut holes in aluminum, copper, iron, stainless steel and zinc.  The hole saws also have a tooth "pitch" that varies from 4 to 6 teeth per inch.  This reduces harmonics and improves performance.  Also, the variation in depth of gullets  between the blade's teeth provides more efficient chip clearance, giving you greater cutting speed.