Teeth Per Inch (TPI)
Affiliate link — we may earn a commissionTPI counts the number of teeth in one inch of blade length. Reciprocating saw and jigsaw blades are spec'd in TPI rather than total tooth count. Low TPI (3 to 6) cuts fast and rough through framing lumber, nail-embedded wood, and demolition material. High TPI (14 to 24) cuts slower but smoother through metal, thin sheet goods, and finish work. A 6 TPI blade rips through a 2x4 in seconds but leaves a ragged edge. A 14 TPI blade makes a clean cut in sheet metal but crawls through lumber.
Why It Matters
Wrong TPI for the material either bogs the tool down or leaves a useless edge. Keep a few blades on hand: 6 TPI for demo and rough wood, 10 TPI for general purpose, and 18+ TPI for metal. Switching blades takes 5 seconds and saves 5 minutes of cleanup.