How to Match Reciprocating Blade TPI to Metal Thickness

Quick answer

Match the blade's teeth per inch (TPI) to the metal thickness: use 18T for thin sheet metal and nail-embedded wood, and 14T for thicker structural metal. A bi-metal reciprocating blade is the right starting point for most metal cutting because the high-speed steel teeth hold an edge while the flexible body resists snapping.

Match TPI to Metal Thickness in 4 Steps

1. Measure the metal thickness: Use calipers or a tape measure to get the exact thickness of the material you plan to cut. For stacked or bundled metal, measure the total thickness of the bundle, not just one piece. Common mistake: cutting thin sheet with a coarse blade, which grabs and bends the metal. If you cannot measure, start with the tooth count that matches the thickest part of the cut.
2. Match TPI to thickness: For thin metal (under 1/8 in), choose a blade with 18 TPI or higher. For medium metal (1/8 in to 1/4 in), use 10-14 TPI. For thick metal (over 1/4 in), use 6-10 TPI. The 18T blade suits thin sheet and nail-embedded wood; the 14T blade suits general metal and thicker stock. Check the material thickness before you open the blade pack, not after the first cut stalls.
3. Match the blade length to the workpiece: Use a 6-inch blade for tight spaces and small workpieces, and a 12-inch blade when you need more reach or are cutting through wider stock. Longer blades flex more, so switch to the shorter option for precise cuts in confined areas. If you cut mostly in corners or near edges, choose the shorter blade even when the material is thick.
4. Select a bi-metal blade for mixed or nail-embedded material: Choose a bi-metal blade when the cut may hit nails, screws, or other hard inclusions. Bi-metal construction resists tooth breakage better than standard high-carbon steel, so it keeps cutting when you hit something unexpected. For demolition or remodeling work, bi-metal is the safer default than standard steel blades.
5. Match the tooth count to the material thickness: Use a coarse blade (fewer teeth, such as 14T) for thick metal so the gullets can clear chips, and a finer blade (18T or more) for thin metal and sheet stock so at least two teeth stay in contact with the work at all times. If the blade chatters or jumps, the TPI is too low for the material thickness; switch to a finer tooth count.
6. Check the blade length and thickness: Match the blade length to the depth of the cut and the blade thickness to the material. A 6-inch blade suits tight spaces and thinner stock, while a 12-inch blade reaches deeper cuts and heavier material. The 0.050-inch thickness of the 12-inch blade adds rigidity for longer cuts, while the 0.035-inch blade stays flexible for tighter curves. Use the shortest blade that reaches the cut; a longer blade is more likely to wander.
7. Match TPI to the material: For thin metal (under 1/8 inch), choose a higher TPI blade such as 18T. For thicker metal, a lower TPI blade such as 14T removes material faster but leaves a rougher cut. The 6-inch 18T blade suits thin sheet metal and nail-embedded wood; the 12-inch 14T blade suits thicker stock and demolition work. When in doubt, pick the higher TPI for thin metal and the lower TPI for thick metal — the blade should always have at least two teeth in the material at all times.

Product facts

• 6" x .035" x 18T Bi-Metal Reciprocating Blade - 10 Pack: 6" x .035" x 18T Bi-Metal Reciprocating Blade - 10 Pack, MADE IN USA, constructed from durable bi-metal for high-performance cutting power. The 18-tooth count suits fast, clean cuts in thinner metal, wood, and plastic where you want less vibration and a smoother edge.

  

• 12" x .050" x 14T Bi-Metal Reciprocating Blade - 10 Pack: 12" x .050" x 14T Bi-Metal Reciprocating Blade - 10 Pack, MADE IN USA, constructed from durable bi-metal for high-performance cutting power. The 14-tooth blade is the better pick for thicker metal because fewer teeth clear chips faster and reduce binding on longer cuts.