The number of teeth per inch as measured from gullet to gullet. Blades with a high TPI deliver smooth, slow cuts and are ideal for cutting metal.
A strip of high-speed tool steel is precision welded to a flexible carbon blade, such a construction provides the best combination of cutting performance and fatigue life.
The advantages and disadvantages of each of the metals are applied in the best locations. The teeth are harder, but also brittle; meanwhile, the body area of the band is softer, but less brittle, and thus more resistant to cracking and breaking.