Reciprocating Saw Blade TPI Explained for Wood, Metal, and PVC

As an Amazon Associate I earn from qualifying purchases. This post may contain affiliate links at no extra cost to you.

Tooth count is the single easiest way to get the right cut from a reciprocating saw. Pick the wrong TPI and you will burn wood, shred PVC, or strip teeth on metal. Get it right and the same saw will cut fast and clean across all three materials.

What TPI Actually Means

TPI stands for teeth per inch. It is counted along one inch of the cutting edge. Low TPI means big, aggressive teeth with deep gullets. High TPI means small, fine teeth packed close together.

Low TPI (2-6) clears material fast but leaves a rough edge. High TPI (14-24) cuts slower but smoother and puts less stress on each tooth. The other rule that matters is tooth engagement: you want at least 3 teeth in the material at all times, ideally 6 to 12. If only one or two teeth are contacting the work, teeth catch, bend, and snap off. If too many teeth are in the cut, gullets clog and the blade overheats.

Blade thickness and tooth geometry matter too, but for wood, metal, and PVC, TPI selection fixes 80% of problems before you pull the trigger.

TPI for Wood: Speed Over Smoothness

Wood is soft, fibrous, and thick. You need large gullets to eject sawdust and prevent the blade from binding. For most wood cutting with a reciprocating saw, stay low.

For demolition, nail-embedded wood, and fast pruning cuts, use 3-6 TPI. A 5 TPI wood-cutting blade rips through a 2×4 in 3-5 seconds with a standard 12-amp reciprocating saw. The cut will be rough and splintered, but speed is what you want when cutting framing, pallets, or branches. These blades usually have an aggressive hook angle and variable tooth spacing to reduce vibration.

For clean wood cuts where appearance matters, like trimming a door jamb or cutting plywood, step up to 6-10 TPI. You will cut about 30% slower, but tear-out is significantly reduced. Above 10 TPI in solid wood, the blade clogs quickly, friction builds, and you will see scorch marks from heat.

If you expect nails, screws, or staples, do not use a plain carbon steel wood blade. Use a bi-metal demolition blade in the same 6-11 TPI range. The teeth are hardened but the body flexes, so hitting a nail dulls the edge instead of snapping the blade. For general wood work, a set of reciprocating saw blades for wood in 5-6 TPI and 8-10 TPI covers 90% of jobs without needing specialty blades.

Failure mode to watch: using a high-TPI metal blade on wood. It will cut, but slowly, and the fine teeth pack with sawdust. The blade overheats, wanders, and can bow in the cut.

TPI for Metal: Fine Teeth and Patience

Metal needs fine teeth, slow feed pressure, and a blade that can handle heat. The rule is strict here: thicker metal can use a lower TPI, thinner metal needs a higher TPI to keep enough teeth engaged.

Use 14-18 TPI for most metal cutting, including unistrut, angle iron, steel pipe, and bolts up to 1/4 inch wall thickness. For sheet metal, auto body panels, and EMT conduit under 1/16 inch thick, use 18-24 TPI. If you use 14 TPI on 20-gauge sheet, one tooth will grab the edge and rip the sheet or strip the teeth.

Speed drops a lot compared to wood. Expect 20-40 seconds to cut through 1-1/2 inch steel pipe with an 18 TPI bi-metal blade, and you need to let the blade do the work. Pushing hard does not make it cut faster. It just overheats the teeth and softens the edge, which is the most common way people kill metal blades.

Always use bi-metal or carbide-tipped blades for metal. Plain high-carbon steel will dull after one or two cuts in steel. A quality bi-metal reciprocating saw blade for metal in 14 and 18 TPI is the cheapest way to get consistent life. You do not need carbide unless you are cutting stainless, cast iron, or doing dozens of cuts per day. For occasional DIY steel cutting, bi-metal is fine and costs far less.

Failure mode to watch: too few teeth in thin metal. If you hear a loud chatter or see teeth missing after a cut, your TPI was too low for that thickness. Also, running the saw at full orbital action on metal will hammer the teeth. Turn orbital action off for metal.

TPI for PVC and Plastic: The Middle Ground

PVC, ABS, and other plastics melt if you get this wrong. They are softer than metal but will gum up a coarse wood blade and crack with a very fine metal blade if you force it.

The sweet spot for PVC pipe and trim is 10-14 TPI. That range is fine enough to avoid chipping the plastic but coarse enough to clear chips before they melt. For PVC pipe from 1-1/2 inch to 4 inch diameter, a 10-12 TPI blade gives the cleanest, most controllable cut. For thinner PVC trim, vinyl, or plexiglass under 1/4 inch thick, use 14-18 TPI to prevent the blade from grabbing and cracking the edge.

Heat is the enemy here. If you see white PVC turning glossy or forming melted burrs along the cut, you are either using too high a TPI or running the blade too fast with too much pressure. Use a moderate speed, short stroke if your saw allows it, and avoid orbital action. Let the teeth shave the plastic instead of friction-melting it.

You do not need a dedicated plastic blade for occasional plumbing cuts. A 10-14 TPI wood/metal combo blade or even a standard 14 TPI bi-metal blade works cleanly on PVC if you keep the speed down. If you cut a lot of plastic, look for blades labeled for PVC or with a ground, sharp tooth profile rather than a wavy set. A general purpose 10-14 TPI reciprocating saw blade is often marketed as a wood/metal combo and it is the best compromise for PVC.

Failure mode to watch: using a 3-6 TPI wood blade on PVC. The large teeth hook the pipe wall, yank the saw forward, and can crack the fitting. Using 24 TPI on PVC creates fine dust that melts and re-welds behind the blade, locking it in the cut.

TPI Comparison by Material

Use this as a buying guide. If a job involves mixed materials, default to the TPI for the thinnest material you will cut.

Tooth Design, Length, and When Cheap Is Fine

TPI is not the only factor. Variable TPI blades, like 8-12 or 10-14, vary the spacing to reduce harmonic vibration. They cut smoother than a fixed TPI and are worth the small premium for demolition and mixed-material work.

Blade length matters for tooth engagement. A 6-inch blade is fine for wood up to 4 inches thick and for most metal. A 9-inch or 12-inch blade is needed for larger PVC pipe or when cutting through walls, but longer blades flex more and wander if you use too high a TPI.

For tooth material, plain high-carbon steel is cheapest and cuts wood fast, but it dulls instantly on nails or metal. Bi-metal is the best value for most people. It costs $2 to $4 per blade in multi-packs but lasts 5x to 10x longer when you hit unexpected metal. Carbide is only justified if you cut abrasive materials like fiber cement, cast iron, or stainless regularly. It costs 3x to 4x more and is brittle if you bend it.

You do not need the most expensive pack to get good results. For a homeowner who cuts a few branches, some PVC, and occasional metal, a 15-25 piece bi-metal assortment with 6 TPI, 10-14 TPI, and 18 TPI blades will handle everything for a year or more. Buy in bulk and treat blades as consumables. A dull high-TPI blade is far worse than a fresh cheap one.

Mistakes That Ruin Blades and Cuts

The most common error is running one blade for everything. A 6 TPI wood blade will destroy itself on steel, and an 18 TPI metal blade will burn wood and melt PVC. Switching blades takes 10 seconds and saves $3 blades.

Second is not matching TPI to thickness. If you have to cut both 3/4 inch plywood and 1/2 inch steel pipe on the same job, use two blades. Compromising with one middle TPI means both cuts suffer.

Third is feed pressure and speed. Let a low-TPI blade pull itself through wood at full speed with orbital action on. For metal and PVC, turn orbital off, reduce speed to about half, and use light, steady pressure. If you see smoke on wood, melted chips on PVC, or blue discoloration on a metal blade, you are too hot. Back off and let the teeth cut.

Check the gullets after a test cut. If they are packed solid, your TPI is too high for that material. If the cut edge is chipped or the blade grabs violently, your TPI is too low.