In general, blades with a lower number of teeth per inch deliver faster cuts with rougher edges. A blade with a higher number of teeth per inch results in smoother, slower cuts and is preferred for metal, which should be cut slowly. When cutting metal, slow down the saw to extend your blade life, and remember, when choosing the TPI, always have 3 teeth in the cut.
Reciprocating saw blades are available for a variety of materials and uses including metal cutting blades, wood cutting blades, blades for composites, for drywall, and other materials. Many of these blade types have a variety of tooth designs intended for special purposes, such as tree-limb cutting, demolition work, clean cutting, or contaminated materials.