Squaring Up A Hollow Chisel

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When setting up a hollow chisel mortiser to make a cut, it’s important that the chisel be set square to the machine fence. If it’s cocked, your mortise wall won’t be flat and smooth, compromising the strength of the joint. To set larger chisels, it’s easy enough to press a small machinist’s square against the fence and chisel to check the angle. However, getting a read on a smaller chisel this way can be difficult, especially for weak or mature eyes.

Instead, try this: First, secure your fence at the desired distance from the chisel, and place a small rare-earth magnet against the outward face of the chisel. Then place a steel 6" rule against the inward face. The ruler serves as a long reference surface for gauging parallelism (and thus square) to the fence. Simply measure to the fence from each end of the ruler, rotating your chisel as necessary to bring the rule and fence into perfect alignment.

—Paul Anthony, senior editor