compass plane

A compass plane has a sole that curves convexly along its length, allowing it to sit flat against concave (hollow) surfaces in curved woodwork. The curved bottom is its defining feature, and it works like any bench plane: a blade set at a shallow angle shaves wood as you push the tool forward. Without that curved sole, a standard plane would rock on its corners and skip across the hollow, leaving tearout and an uneven surface.

The sole's radius must match or approximate the concave curve of the workpiece. A single compass plane typically works within a limited range of curves; woodworkers often own several, each ground to a different radius. The sole is often made of wood (beech, boxwood, or hornbeam) with a steel blade bed and iron sole piece, though all-metal versions exist. The blade itself is usually narrower than a jointer plane, often 1.5 to 2 inches wide, and sits at around 45 degrees, similar to a jack plane.

These planes are essential when smoothing the inside of chair seats, the concave curves of decorative work, or the hollow sections of turned legs and spindles. They appear frequently in period furniture restoration and in shops that do hand-carved or steam-bent components. Modern curved scrapers and random-orbit sanders have reduced their daily use, but they remain the fastest way to remove planing marks from a concave surface without needing electricity or leaving swirl marks.

The tool is sometimes called a compass jointer when the sole curves very gently over a long distance, useful for smoothing long, shallow hollows. More sharply curved versions grade toward the toothing plane territory. The name reflects its purpose: it follows the compass (the arc) of the curve rather than forcing a flat plane against a curved surface. Setting and tuning the blade requires care, since the toe and heel must be perfectly coplanar with the curved sole to avoid dubbing the edges.