Jigs

Zero-clearance on a mitre saw

Kerf plates and a wooden facing: clean bottom edges, a visible cut line, and offcuts that stay out of the blade.

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Around the blade of a mitre saw there's a slot in the table and a gap in the fence. When you cut, the fibres on the bottom and back edges have nothing behind them there, and they tear out. The gap also hides exactly where the blade will pass, and a small offcut can drop into it or jam against the blade. Close the gap to exactly the width of the blade, and all three problems largely go away.

The cut end of a piece lying on the saw table against the fence. The arrow shows the teeth travelling down and towards the fence. On the left, without a facing, splinters are torn out along the bottom edge and the edge against the fence, where the teeth come out of the wood. On the right, a thin wooden facing under and behind the piece backs those edges and they stay clean
The teeth come out of the wood at the bottom and on the fence side, and that is where it tears. The facing backs those edges.
Two sections across a cut, the blade going down through a board. On the left the board lies over a wide slot in the saw table and its bottom edges splinter on both sides of the cut. On the right the board lies on a wooden base with a kerf exactly as wide as the blade, so the bottom edges stay clean
Left: a wide slot and torn fibres underneath. Right: a base with a kerf the width of the blade.

Kerf plates

Many mitre saws have sliding plates in the table on either side of the blade. Loosen them, slide them in until they nearly touch the blade, and tighten them. For the smallest gap, push the plates together and cut slowly through them with the blade.

A mitre saw table from above: the slot around the blade with two plates on either side, each pushed in towards the blade, as the arrows show, until only the blade fits between them
The plates pushed in to the blade from both sides.

On a sliding saw, check the whole length of travel: the blade mustn't touch a plate with the head pulled towards you or pushed back to the fence. After changing the bevel, set the plates again. Replace worn ones. DeWalt says to do it once the slot is wider than 10 mm.

A wooden facing

An older mitre saw on a garden workbench, with a wooden board screwed to the fence on both sides of the blade and an offcut block on the table
A wooden board screwed to the fence. Photo: Santeri Viinamäki (opens in a new tab), CC BY-SA 4.0 (opens in a new tab).

When there are no plates, or you want to close the gap in the fence too, make an L-shaped wooden facing: a base for the table and an upright board for the fence. The base should be at least as deep as the table, and the upright taller than the stock you cut. Use straight plywood of even thickness, such as 12 mm. Glue the two parts together and screw the upright to the fence through the fence's holes, with the screw heads sunk into the wood.

On a sliding saw, lock the head pushed back to the fence and make three cuts: at 0° and at 45° each way. The base has to be deep enough that the blade doesn't cut right across it. At least 7 cm of solid wood should stay at the front. With the facing on, don't swing the table with the head lowered, or the blade will cut into the facing.

A mitre saw from above with an L-shaped wooden facing: a board screwed to the saw fence and a base on the table. Three kerfs run through it from the middle of the fence, one straight at 0° and two at 45° left and right. A piece lies against the facing with its pencil mark on the edge of the straight kerf
Three kerfs: 0° and 45° each way. Put the mark on the piece at the edge of the kerf.

Working with the facing

Put the mark on the piece at the edge of the kerf, on the waste side, and you can see at once where the blade will pass. Each angle and bevel cuts its own kerf, so the facing weakens with time. When, after many cuts at different angles, it no longer supports the work well, replace it.

The kerf only fits the blade that cut it. Fit a thicker or thinner blade, let alone move to another saw, and the gap is no longer zero, so you need a new facing. If you cut at different angles a lot, make several facings, for example one for 0° cuts and another for 45°.

Before the first cut, bring the lowered blade through its whole travel with the saw switched off, and check that it doesn't catch the facing anywhere. Keep your hands at least 100 mm from the blade, as the Makita and Bosch manuals say, while DeWalt gives 152 mm. After the cut, wait for the blade to stop before you take the offcuts away.

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