Dadoes, Rabbets, and Grooves

Three cuts

These are the bread-and-butter joints of casework - bookcases, cabinets, chests, drawers:

• Dado (also called a housing): a flat-bottomed channel across the grain. Shelves and dividers sit in dadoes in the case sides.
• Groove: the same channel running along the grain. Panels, drawer bottoms, and box bottoms sit in grooves.
• Rabbet: an L-shaped step cut along an edge or end. Cabinet backs sit in rabbets at the back of the sides; drawer fronts and box lids often use them.

A stopped dado or groove ends before the edge so it doesn’t show from the front.

Proportions

• Dado depth: about one-third of the side’s thickness (about 1/4 inch in a 3/4-inch side).
• Groove for a panel or bottom: about 1/4 inch wide and deep, set back 1/4 to 1/2 inch from the edge.
• Rabbet for a back: as deep as the back is thick and about half the side’s thickness wide.
• Fit shelves snug but not forced; a dado that’s too tight splits the side when the shelf is driven in.

By hand

Dado (housing) ¹:

1. Knife both walls across the board, using the shelf itself to mark the width.
2. Pare a small V on the waste side of each line to create a knife wall.
3. Saw down both walls to depth with a backsaw, guided by the knife walls.
4. Chisel out the waste from both edges toward the middle.
5. Level the floor to an even depth with a router plane (a flat-soled plane with an iron that hangs down to a set depth).

Groove: a plow plane has a fence that rides the board’s edge, a depth stop, and interchangeable narrow irons. Plow from the far end of the board, starting with short strokes and working back, until the depth stop rides the wood ².

Rabbet: a rabbet plane or moving fillister (with fence, depth stop, and a nicker for cross-grain work) cuts rabbets. Or saw and chisel, or plane down to gauge lines on two faces.

By machine

• Table saw with a dado stack or multiple passes (guard and riving knife can’t always be used, so take extra care).
• Router with a straight bit and an edge guide or a straightedge, in multiple passes.
• Router table for grooves and rabbets on small parts.

Strength and movement

A dado alone mostly resists the shelf’s weight; it doesn’t keep a case from racking or the sides from spreading. Add a back in a rabbet, a fixed top, or through-tenons or nails through the side into the shelf ends. Panels in grooves float - they’re never glued all around (see Frame and Panel), and a drawer bottom in a groove is left free to move, fastened only at the back.

What to take from this

Dadoes run across the grain (shelves), grooves along it (panels, bottoms), and rabbets step an edge (backs). Make dadoes about a third of the side’s thickness. By hand: knife, wall, saw, chisel, and level with a router plane; plow grooves with a plow plane; cut rabbets with a rabbet plane. Add backs or tenons for racking strength, and let panels and drawer bottoms float.