Router Plane: Precision Depth Control

Last reviewed on 2026-04-24

The router plane — the old woodworker's name for it is the "old woman's tooth" — is an open-throated plane with a narrow iron that drops down from a flat reference base. Its one job is to level the bottom of a recess to a consistent depth below the surrounding surface. No other hand tool does this as reliably, which is why the router plane is the go-to tool for inlay, for hinge mortises, and for the bottoms of dados and grooves.

Why Router Planes Matter

The bottom of a dado chopped by chisel is a series of facets; the bottom of a groove run with a plow is close but not quite flat. Both will hold together, but both are visibly uneven and can telegraph through a panel or leave a gap in a drawer bottom. A router plane sets its iron to a measured depth below the base, and then you push it across the bottom of the recess. Any high spot is cut, any low spot is ignored, and the base keeps you from going deeper than the setting. The bottom ends up flat and at a depth that matches across the entire joint — which is exactly what glue, inlay, and hinges all need.

Common Uses

Dados and grooves: level the bottom after initial excavation so a drawer bottom, shelf, or divider seats evenly.
Hinge mortises: set depth so every hinge sits exactly flush with the face of the door and jamb.
Inlay: excavate a shallow recess to a precise depth so the inlay sits flush with the surrounding surface after glue-up.
Tenon cheek refinement: reference the face of the tenon's shoulder to bring the cheek to a consistent thickness across the width of the joint.

How the Plane Works

The iron is mounted vertically in a yoke that moves up and down in the body. A knurled adjustment nut raises or lowers the iron in small, repeatable increments. The base rests on the surface around the recess (or on a spanning straightedge for deeper work) and the iron cuts only as far below that reference as the adjustment sets.

Irons are narrow — commonly 1/4 inch and 1/2 inch — so the plane can reach into narrow dados. A few models take pointed "spear" irons for getting into corners.

Setup and Technique

Sharpen the iron's flat and bevel like any other plane iron. It does not need to be polished like a smoother, but it must be keen.
Install the iron and back the adjustment off until the edge sits above the sole.
Place the plane on the reference surface next to (not inside) the recess. Advance the iron until it just kisses the surface — this is your zero.
Place the plane in the recess and cut. Progressively lower the iron a few thousandths at a time, making a pass at each setting, until the full floor of the recess is clean and the plane cuts only air on a final pass.

Buying Notes

The Stanley No. 71 (with handles) and No. 71½ (no handles) are the classic metal router planes. Both are widely available on the used market and, once tuned, do everything most woodworkers need. Modern alternatives from Veritas and Lie-Nielsen are excellent. A small palm router plane for inlay work is a useful second tool but not a substitute for a full-size router plane.