Digital Angle Gauge

A digital angle gauge is a small box with an inclinometer, a display and magnets in the base. Set it on a reference surface, zero it, then set it on the surface you are measuring and read the difference.

Why the built-in scale is not enough

Every saw has an angle scale, and the detents at 90 and 45 are convincing. They are also frequently wrong -- knocked out by transport, drifted with wear, or never right from the factory. A blade half a degree off square produces a mitre joint that is a full degree open across the pair, and a four-sided box that will not close.

The gauge measures the actual blade, not the mechanism's opinion of the blade.

Using one

Zero it on the reference, not on the bench. This is the part people get wrong. Put the gauge on the saw table, press zero, then move it to the blade. You have now measured the blade relative to the table, which is the angle that matters, and any tilt in the bench or the floor cancels out.

• Read against the blade plate, not the teeth. Teeth are set alternately left and right; the gauge will rock on them. Find a flat spot on the plate between teeth.
• Unplug the saw. You are putting a metal object against a blade.
• Beware swarf on the magnets. A steel chip trapped under the base tilts the gauge and it will lie to you confidently.
• Check the battery. These drift as the cell dies, and a wrong reading is worse than no reading.

Also useful for setting a bevel on a jointer fence, checking a drill press table, transferring an existing angle off a piece of furniture, and confirming a sliding bevel setting numerically.

Not a substitute for a square

For 90 degrees specifically, a good machinist square against the blade is more accurate than most consumer gauges and needs no battery. Use the gauge for arbitrary angles and quick checks, the square for the reference right angle.