18 or 24 TPI for Metal: How to Choose Tooth Count

Neither is better across the board. Pick 24 TPI for thin-wall tube, sheet and light angle, and 18 TPI for general work on slightly thicker stock. The deciding factor is wall thickness: at least three teeth should be in the cut at all times.

The three-tooth rule that decides everything

Every tooth on a band saw blade cuts a small chip and then needs room to carry that chip out of the cut. If too few teeth touch the work, each tooth takes a big bite, snags on the edge and can break off. If too many teeth touch the work, the gullets between them fill with metal and the blade rubs, heats up and dulls.

The common guideline is to keep at least three teeth in the material at any moment. You can work out the thinnest wall each blade handles with simple division: 3 teeth divided by the TPI. That gives about 0.167 in for an 18 TPI blade and 0.125 in for a 24 TPI blade.

Thicker is generally fine as long as the chips can clear. Thinner is where trouble starts, because the teeth straddle the cut and catch. For thin metal, the finer blade is almost always the safer choice.

18 TPI vs 24 TPI at a glance

The table below uses the three-teeth arithmetic from above plus the way each tooth count is typically used. Treat the thickness figures as a floor for a clean cut, not a hard limit.

Factor	18 TPI	24 TPI
Thinnest stock for 3 teeth in the cut	About 0.167 in (3 divided by 18)	About 0.125 in (3 divided by 24)
Typical material	Thin to medium tube, angle, flat bar, sheet stacks	Thin-wall tube, thin sheet, small profiles
Cut speed	Faster, clears chips more easily	Slower, takes smaller bites
Finish	Good for general work	Smoother, less burr on thin parts
Main risk	Stripped or snagged teeth on very thin walls	Clogged gullets and heat on thicker stock

When 18 TPI is the better choice

An 18 TPI blade is the all-rounder for portable band saws. It has enough teeth to handle thin-wall material, yet the gullets are large enough to clear chips from heavier cuts. If you cut a mix of electrical conduit, angle iron, flat bar and light pipe, this is usually the blade to keep on the saw.

The published specs on our best band saw blades for metal page show how common this tooth count is for portable saws. The DEWALT DW3983C is an 18 TPI blade, 32-7/8 in long, 1/2 in wide and 0.020 in thick, sold as a 3-pack with 8% cobalt content. The FOXBC 27 in 18 TPI pack lists common materials at 5/32 in to 3/16 in thick and very hard materials at 3/16 in to 5/16 in thick.

Those ranges sit above the 0.167 in floor we calculated, which is why 18 TPI works well there. Stock thicker than about 5/16 in starts to favor a coarser blade, since 18 teeth per inch can load up in a deep cut.

When 24 TPI is the better choice

Choose 24 TPI when the wall is thin. Thin-wall tube is the classic case: a coarse blade can hook the tube edge as it enters and exits, and a fine blade keeps several teeth supported at all times. Sheet, thin angle and small hobby-size profiles belong in this group too.

Our page lists the DEWALT DW3984C, a 24 TPI version of the same 32-7/8 in, 0.020 in thick portable blade, as its pick for thin-wall tube. For horizontal saws, the FOXBC 64-1/2 in blade is a 24 TPI 2-pack that lists compatibility with models such as the WEN 3970, Grizzly G0622 and JET HBS-56S.

The tradeoff is speed and heat. Fine teeth cut more slowly, and on thick solid bar they can fill up with chips. If a 24 TPI blade glows, smokes or stops cutting on thick stock, you have probably gone too fine.

How to choose in four steps

Use this quick process before you buy or swap a blade.

Measure the wall thickness at the point where the blade enters the metal, not the overall size of the part. For tube, that is the wall, not the diameter.
Divide 3 by the thinnest wall in inches. If the answer is 24 or higher, go with 24 TPI. If it lands around 18, go with 18 TPI.
For a mix of jobs, pick for the thinnest material you cut often. A blade that is slightly too fine is more forgiving than one that is too coarse.
If your stock is much thicker or you cut varied pipe and profiles, look at coarser or variable-pitch blades instead. Our comparison covers 10/14 variable options for exactly that.

What matters as much as tooth count

Tooth count only works if the rest of the setup is right. Blade material is the first thing to check. Bi-metal blades with high speed steel or M42 cobalt teeth hold an edge much longer in metal than carbon blades, and both of the DEWALT blades above list 8% cobalt content.

Blade speed is the second. Metal needs slow blade speeds, and Imachinist suggests 100 FPM to 300 FPM for ferrous metals. Running too fast burns the teeth quickly, whatever the TPI.

Length is the third. The blade must match your saw exactly, from 27 in compact portable saws to 93.5 in shop saws, so check your manual or the old blade first. You can compare lengths and tooth counts side by side on the band saw blade comparison.

Safety notes

Cutting metal throws hot, sharp chips and leaves razor-edged burrs. Wear safety glasses or a face shield, and use hearing protection with portable saws, which can be loud against steel. Wear gloves when handling fresh cuts and used blades, but keep them away from the moving blade.

Clamp the work firmly so it cannot twist or pinch the blade. Unplug a corded saw or remove the battery before changing a blade. Let blades and parts cool before touching them, since friction heats both.

Frequently asked questions

Can I use 24 TPI on thick steel?

You can, but it is usually a poor fit. The teeth fill with chips, the blade heats up and cutting slows. Use a coarser blade for thick solids.

What happens if my blade is too coarse for thin tube?

Too few teeth touch the thin wall, so each tooth grabs the edge. That can chatter, tear the tube or strip teeth from the blade.

Do 18 and 24 TPI blades fit the same saw?

Yes, if the length, width and thickness match. The DEWALT DW3983C and DW3984C are both 32-7/8 in long, 1/2 in wide and 0.020 in thick, and differ in tooth count.

Is a variable-pitch blade a better option than either?

It can be for mixed work. Variable pitches like 10/14 suit pipe and profiles with changing wall thickness, while 18 or 24 TPI suit consistently thin stock.