When the blade misbehaves.

Most bandsaw trouble comes down to a few things: the blade itself, its tension, the guides and the way the work is fed. Before you blame the machine, work through the likely causes below, starting with the cheapest to check. Your manual has the settings for your saw; this page only helps you find where to look.

The blade breaks.

• Fatigue. A blade bends round the wheels with every turn. Look along the back edge and in the gullets, the hollows between the teeth: fine cracks there mean the blade is worn out, and it will break soon. Replace it.
• Too thick for the wheels. A thick blade on small wheels fatigues quickly. Stay within the thickness your manual gives.
• Guides set wrong. If the guides pinch the blade, or the rear thrust bearing presses on it all the time, the blade heats up and cracks. With no work in the saw, the blade should run clear of the guides and the thrust bearing.
• Forcing it. Pushing too hard, or forcing a curve tighter than the width allows, overloads the blade. See blade width and curves.
• The weld. If a fairly new blade breaks at the weld, the weld is the likely cause. Tell the supplier; a good weld should outlast the teeth.

The cut drifts off the line.

• A dull or damaged blade. If the teeth on one side are duller or have hit something, the blade pulls towards the sharper side. A new blade often cures drift on its own.
• Too little tension. A slack blade wanders, especially in thick wood. Check the tension your manual gives for the blade width.
• Feeding too fast. Let the blade cut at its own pace.
• Natural lead. Even a good blade can cut slightly off square. For straight cuts, find its drift and set the fence to it, as described in resawing.

The wood burns.

• A dull blade rubs instead of cutting.
• Too many teeth for the thickness: the gullets fill with sawdust. Choose a coarser blade; see choosing TPI.
• Resin on the blade. Pitch from resinous wood builds up on the teeth and sides. Clean the blade with a blade or resin cleaner, following the cleaner’s instructions.
• Feeding too slowly or pausing mid-cut lets the teeth rub in one place.

The cut is wavy or bellied.

A cut that wanders in and out, or bows in the middle of a tall board, usually means the blade is flexing in the cut: too little tension, a blade too narrow or too fine for the depth, a dull blade, or feeding too hard. Raise the tension to the manual’s setting, lower the upper guide to just above the work, and use a wider, coarser blade for deep cuts.

Teeth break off.

Teeth strip when too few are in the cut, so each one takes too big a bite: a coarse blade in thin material, or the edge of a tube. Follow the three-teeth rule. A nail or screw in reclaimed wood will also take teeth out; check old boards with a metal detector first.

The blade comes off the wheels.

Check the tracking and tension first, then the tyres: worn, cracked or loose tyres let the blade wander across the wheel. Backing out of a long curved cut while the saw is running can also pull the blade forward off the wheels; if you need to back out, go slowly, or switch off and wait for the blade to stop.