How do you achieve a controlled surface texture on an inside, compound curve? One approach is a gouge, but a gouge has no fixed depth and therefore offers limited control as a repeatable variable. In contrast, historical Japanese woodworking employs the mameganna, or “bean plane”: a compound-curved plane for adjustable cutting depth directly to a fixed compound curvature within the tool geometry.

This allows subtle, consistent texturing as well as rough shaping, even within deeply concave forms such as the bowl of a spoon, and still operates as a highly efficient historical system—one that produces results at a speed equal to router tooling, but with greater surface finish and adjustability.