What is a compass, or circular, plane?
What it's used for
Curves and circles
Compass, or circular, planes are for planing convex (external) and concave (internal) curves in wood.
Metal versions can handle any anything from a slight curve in the arm or leg of a chair to a complete circle such as a round table top.
Metal version are more restricted is use - see Characteristics below
The workpiece is first sawn roughly into the curved or circular shape.
The curve of the plane's sole is then adjusted – by turning a large nut or wheel – to match the curve.
Go with the grain
It's important to reposition the workpiece as necessary to ensure planing goes with the grain at all times to avoid tear-out of the wood fibres.
Uniquely, the sole of the metal compass plane is made from a flexible steel sheet that can be adjusted steplessly to form varying, uniform, concave and convex shapes.
Steplessly means continuous adjustment without any predetermined, set positions.
Limited scope of wooden compass planes
Wooden compass planes – available second-hand only except for ones made by a very few specialist plane makers – are limited in scope compared to metal ones. Wonkee has only been able to find ones that have convex soles, so they can only be used to cut relatively shallow, concave curves.
Available as old, used tools on some internet sites, they can be useful for hollowing out chair seats and shallow bowls.
Some wooden compass planes have adjustable blocks on the toe that can be adjusted up and down, effectively altering the radius (the degree of curvature) at which the plane cuts.
Lowering the adjustable block has the effect of tilting the plane upwards at the front end, which increases the radius. Moving the block upwards reduces the radius until the block's bottom edge is in line with the sole, at which point the plane is set to its smallest possible radius.
Although they skipped some numbers, Stanley didn't dodge the number 13 when it came to allocating plane model numbers.
The No. 13 is a compass plane made between 1871 and 1909, and is not easy to find these days. You might have better luck seeking out later models such as the No. 20 and No. 113, or a new plane based on one of those designs.