What's inside
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A compass plane is a hand plane with a flexible sole that can be set to a convex or concave curve. It is useful for fairing curved timber edges on chair parts, rails, bows and other work too small or awkward for a spokeshave. The adjustable sole is also its main complication: set it too aggressively and the plane digs in; set it too flat and it barely cuts.
Check the curve before planing
Mark the finished curve clearly and leave a small amount of waste—about 1 mm is usually enough for final shaping. If the edge is rough or well outside the line, remove most of that waste with a coping saw or bandsaw first. A compass plane is a shaping and fairing tool, not an efficient way to remove a deep wedge of timber.
Check the curve with a flexible batten, a template or a set of measurements from the drawing. Look for abrupt changes in curvature: a curve that tightens sharply can catch the plane even if the overall shape looks smooth. Secure the work so it cannot rock. For a narrow rail, clamp it close to the edge without placing a clamp where your hands or the plane need to travel.
Set the sole to the curve
Most compass planes adjust by turning a screw or lever that bends the sole. A convex sole suits an outside edge; a concave sole suits an inside curve. Make small adjustments and check the shape against the work or a template. There is no useful universal setting: the right curve depends on the workpiece.
Set the sole slightly flatter than the tightest part of the curve, then test the plane on offcuts of similar timber. If it rocks on the work or contacts only at one small point, ease the adjustment. If the sole bridges a hollow and leaves the ends cutting, increase the curve a little. A sole set too tightly can concentrate pressure at the toe or heel and cause a hollow or gouge.
Extend the blade just enough to take a fine shaving. On a test piece, aim for a continuous shaving around 0.1–0.3 mm thick. If the plane leaves torn fibres rather than a clean cut, retract the blade, sharpen it and try again. A curved sole does not compensate for a dull iron.
Plane in controlled passes
Start with short, light strokes, following the length of the curve rather than trying to plane across its width. Keep the plane moving as the blade meets the timber; pausing under pressure can leave a flat spot. On an outside curve, work from the high areas towards the line. On an inside curve, use short strokes and watch the toe: it can catch at the entry if the plane is set too aggressively.
Check progress every few passes. A pencil line drawn across the edge is a quick indicator: if one area loses its mark much faster than the rest, you are cutting unevenly. Use a straightedge or flexible batten to find flats, and compare the edge to the template rather than relying on sight alone. Stop with the plane as soon as the curve is fair and close to the line. Use a scraper or abrasive paper wrapped around a suitably shaped block for the final few tenths of a millimetre; sanding alone can soften the edge and make a precise curve harder to hold.
Manage grain and tear-out
Changing grain direction is common on curved parts, and a plane that cuts cleanly on one section may tear the next. Keep the cut shallow. If fibres lift ahead of the blade, try planing from the opposite direction on that section, or skew the plane slightly so the blade slices rather than pushes straight into the grain. A freshly sharpened iron matters more than extra pressure.
Support thin or fragile work close to the edge. If the timber is prone to splitting, leave more waste for a few passes and keep the work firmly clamped. Do not force the plane through a tight curve: chatter, a sudden heavy shaving or a chipped edge are signs to stop and reset the sole, blade or workholding.
Choosing a compass plane
Compass planes vary in sole length, adjustment range and how easily they hold a setting. A longer sole bridges small irregularities and suits broad, gentle curves; a shorter sole follows tighter curves but can make dips easier to plane into the work. If you only have an occasional curved edge to shape, a spokeshave or a rasp may be cheaper and simpler. For repeated curved work, an adjustable compass plane offers more control across different radii.
| Tool | Best suited to | Trade-off |
|---|---|---|
| Compass plane | Fairing long, smooth curves and changing radii | Needs careful sole and blade adjustment |
| Spokeshave | Short curves, shaped handles and controlled local work | Less comfortable for some inside curves; takes practice to avoid hollows |
| Rasp or file | Removing small amounts of waste, including awkward grain | Leaves a rougher surface that needs scraping or sanding |
For a first purchase, compare a adjustable compass plane with a spokeshave. The plane is the more versatile choice when curves vary in radius; the spokeshave is often the better-value tool for occasional shaping. A cheap plane can be adequate if its sole adjusts smoothly, locks securely and the blade can be sharpened properly. If the setting slips during a pass or the sole binds, it will cost time regardless of the initial price.
Finish and maintain the cut
Once the edge reaches the line, check it from several angles and feel for bumps with your fingertips. A scraper is useful for removing isolated ridges without changing the whole curve. If you sand, use a shaped block that matches the curve; a finger or loose paper tends to round over the arris.
After use, retract the blade and release tension on the adjustable sole if the maker recommends it. Brush out chips and keep the sole clean. Before the next job, check that the sole still holds its setting and that the blade is sharp. Those two checks prevent most of the common failures: uneven cuts, chatter and an edge that wanders away from the template.