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Band Saw Blades: Carbon Steel, Bi-Metal, Pitch and Tension
A band saw blade is a loop of steel with teeth, and almost every problem with a band saw can be traced back to that loop, its teeth or the tension it runs at. A blade with the wrong tooth pitch packs its gullets and stalls; a blade running slack wanders in the cut; a blade with too fine a pitch burns its way through a thick section. This guide covers the band saw blades in this range and how to match pitch, material and setup to the work.
The four things a blade has to get right
- Tooth pitch. Teeth per inch sets the size of the gullet, and the gullet has to swallow the chip. The rule that matters is at least three teeth in contact with the work at all times.
- Tooth material. Carbon steel for timber and soft material, bi-metal for steel, and carbide when the material is abrasive.
- Tooth set. The alternating offset that makes the kerf wider than the blade body, so the back of the blade does not rub in the cut.
- Tension. A slack blade wanders and dulls unevenly. Tension is what keeps the blade tracking straight and cutting where it was aimed.
Which blade for which material
| Blade | Material | Note |
|---|---|---|
| Carbon steel, hardened teeth | Timber, soft plastics, foam | Fast cutting, low cost, tolerant of resin |
| Bi-metal | Steel, stainless, mixed scrap | Hardened tooth edge on a flexible back |
| Fine pitch | Tube, thin wall, sheet | Keeps teeth in contact on a thin section |
| Coarse pitch | Solid bar, thick timber | Gullets big enough to clear the chip |
Cutting timber
A hardened carbon steel woodworking band saw blade for 8 to 14 inch machines is the blade that gets used most. The teeth are hardened for wear resistance while the body stays flexible enough to run around small wheels, which is the compromise every wood blade has to make. On timber the job is to clear the dust: a blade that is packing the cut is either dull, too fine for the thickness, or being fed faster than the tooth pitch can clear. Resin building up on the blade is the signal that the gullets are not clearing, and cleaning the blade is quicker than ordering a new one.
Cutting steel and mixed material
A bi-metal band saw blade welds a hardened high speed tooth edge to a spring steel back, so the teeth hold their hardness on steel while the body survives the flexing of the wheels. That is why bi-metal is the default blade for cutting steel, stainless and mixed scrap: the same blade will take a length of tube and a piece of solid bar without dying on the second cut. Choose the pitch for the section thickness rather than for the material name, and keep the feed low enough that the teeth cut instead of rubbing.
Tooth pitch is the decision that matters most
Pitch is chosen by the thickness of the material, not by what the material is called. Whatever is being cut, aim for at least three teeth inside the cut at any moment. In a 25 mm solid bar a coarse blade has teeth in the work and clears its chip; on a 2 mm tube wall that same blade puts one tooth in the cut, which strips teeth and grabs the work. On thin tube and sheet, move to a fine pitch, or clamp the work in a way that adds effective thickness. Variable pitch blades, which group teeth in a repeating coarse and fine pattern, reduce the ringing that a constant pitch sets up in a thin wall.
Setting the machine up
- Tension first. Set the blade so that it does not flutter and does not stretch. Re-check after the first cut, when a new blade settles.
- Guides close in. Move the guide arms in until they are just clear of the work. The closer they are, the less the blade can wander.
- Break the blade in. Run the first few cuts at a reduced feed so the sharp tooth corners are eased in. A blade broken in this way lasts noticeably longer.
- Feed and speed. Too much feed strips teeth, too little glazes them. Both failures look the same from the outside: a blade that has stopped cutting.
- Coolant. Use it on steel for cooling and chip clearing, and check the mix, because a weak mix stops lubricating long before it stops cooling.
- Clamping. Support the work on both sides of the cut and clamp it hard. A piece that shifts as the blade enters is what breaks teeth.
Why blades fail early
Blades rarely wear out evenly. They fail at a point, and the point tells you what went wrong. Teeth stripped in a short run usually mean the pitch was too coarse for the wall thickness or the feed was too heavy at the start of the cut. Teeth rounded and shiny mean the blade was rubbing rather than cutting, which is a speed or feed problem. A blade that cracked from the back of the tooth line has been tensioned too hard or has been run with the guides too far apart, so it flexed in the cut. Cuts that come out tapered rather than straight point at the same two causes: insufficient tension, or guides that are too far from the work.
Frequently asked questions
How do I choose the tooth pitch?
By the thickness of the material. You want at least three teeth in the cut at any time, so thin tube and sheet need a fine pitch and solid bar needs a coarse one.
What is the difference between carbon steel and bi-metal blades?
Carbon steel blades are hardened teeth on a flexible body and suit timber. Bi-metal blades weld a high speed tooth edge to a spring steel back, so they survive cutting steel.
Why does my blade keep breaking?
Usually over-tensioning, guides set too far apart, or a feed that is too heavy for the tooth pitch. Check tension and guide position before blaming the blade.
How tight should a band saw blade be?
Tight enough to track straight without fluttering, and no tighter. Over-tensioning shortens blade life and loads the wheels for no gain.
Can one blade cut wood and metal?
Not well. Tooth geometry and material are chosen for one family of work, and a blade used outside it either packs its gullets or strips its teeth.
Where to start
Browse the full Machine Saw Blades range, or the wider Cutting & Measuring Tools category if you also need drill bits, jigsaw blades, squares or gauges. Tell us the machine, the material and the section thickness, and we will point you at the pitch and the tooth material that suit it.
