Which saw blade TPI do I need for the material I am cutting?

The three-teeth-in-the-cut rule, what TPI actually controls, and the right tooth count for timber, sheet, laminate and metal.

Difficulty: beginner
Time: 12 min
Read: 4 min

Short answer

Coarse teeth for thick timber, fine teeth for thin material and metal. The governing rule is that at least three teeth must be in contact with the material at all times: too few and it snatches and strips teeth, too many in thick stock and it clogs, overheats and burns.

TPI — teeth per inch — is not a quality figure, it is a match to the material. The same blade that flies through a joist will chew a sheet of laminate to pieces, and the fine blade that gives a glassy edge in ply will burn to a stop in a fence post.

Choosing blade teeth per inch by material thickness

Step by step

Apply the three-tooth rule first.Count how many teeth would be touching the material at once. Fewer than three and the blade will bite too deeply and snatch; that is what strips teeth off jigsaw and hacksaw blades.
Use coarse blades for thick timber.Around 6 to 10 TPI on a jigsaw or hand saw for structural timber. The deep gullets between teeth carry sawdust out; without that space the blade jams.
Use fine blades for sheet and laminate.Twenty TPI and upwards. More teeth means each takes a smaller bite, so the surface tears far less.
Use very fine blades for metal.Twenty-four TPI for thick section, 32 for thin sheet and tube. Sheet metal in a coarse blade catches and rips the blade to pieces in seconds.
Match the tooth geometry, not just the count.Ground teeth cut cleanly, milled teeth cut fast and rough. Downcut jigsaw blades reverse which face splinters. Both matter as much as TPI.
Think about circular saw blades differently.There TPI becomes total tooth count. Around 24 teeth on a 190mm blade for fast ripping, 40 for general work, 60 or more for laminate and fine crosscuts.
Match the blade to the material as well as the thickness.Blades are sold for wood, metal, plastics, fibre cement and plaster. The tooth material and coating differ, not only the count.
Check the blade is long enough.On a jigsaw or reciprocating saw the blade must pass fully through the material at the bottom of its stroke, or it never clears the waste.
Slow the speed as the TPI rises.Fine blades in hard material generate heat quickly. High tooth count plus high speed equals a blue blade and a burnt cut.

Tips

If a blade is snatching, you have too few teeth in the cut. If it is burning, you have too many.
For a clean cut in laminated board, a fine blade plus masking tape plus a backing board gives an edge that needs no cleaning up.
Keep the cheap coarse blades for anything that may contain nails, and the good fine ones for finished work only.

Common mistakes

Using a wood blade on thin metal — With fewer than three teeth in contact, each tooth takes a huge bite, catches on the edge and shears off. The blade is ruined in a few seconds and fragments can fly.
Using a very fine blade in thick softwood — The tiny gullets fill with sawdust immediately. The blade stops cutting, rubs, heats up and scorches the timber, and often bends.

If it doesn't work

Blade snatching and juddering

Cause: Too few teeth engaged in thin material — Fix: Fit a finer blade so at least three teeth are always in contact, and support the material closer to the cut.

Cut burning and slowing

Cause: Too fine a blade, packed gullets, or a blunt blade — Fix: Switch to a coarser blade, reduce the feed rate and let the blade clear.

Badly torn edge on laminate

Cause: Coarse blade and no support — Fix: Fine or downcut blade, masking tape over the cut line, and a sacrificial board underneath.

Teeth stripped from a jigsaw blade

Cause: Blade too coarse for the thickness, or hit a fixing — Fix: Match TPI to thickness, and check for nails and screws before cutting reclaimed material.

Questions people ask

What does a downcut jigsaw blade do?

It cuts on the down stroke rather than the up stroke, so the teeth exit through the underside and the top face stays clean. It is the right blade for laminate worktops and finished panels.

More teeth on a circular saw blade — always better?

No. High tooth counts cut cleanly but slowly and generate heat, and they are poor at ripping along the grain. A 40-tooth general blade is the best single compromise for most people.

Can I cut metal with a wood circular saw blade?

No. Use a blade specified for metal, at the speed the blade is rated for. A wood blade in steel can shatter.