Dado and Rabbet Joints
A dado is a flat-bottomed channel cut across the face of a board for another board to sit in; a rabbet is a step cut along the edge of a board, open on one side. Both are among the strongest and simplest joints for plywood and MDF furniture: a shelf in a dado rests on the shoulder of the channel, and a back in a rabbet is hidden and locks the cabinet square. Cutting them by hand-held router is explained in how to use a router.
Dado, groove and rabbet
| Joint | Shape | Where | Typical use |
|---|---|---|---|
| Dado | Channel with two walls | Across the face of a board | Shelves, cabinet bottoms, dividers |
| Stopped dado | Dado that ends before the front edge | Across the face | Shelves where the joint must not show |
| Groove | Channel with two walls | Along the grain | Drawer bottoms, panels in frames |
| Rabbet | Step with one wall | Along an edge or end | Cabinet backs, box corners, drawer fronts |
| Dado and rabbet | Rabbet on one part fits a dado in the other | Corners | Drawer and box corners |
How deep and how wide
| Cut | Depth | Width |
|---|---|---|
| Dado in 3/4 in (18 mm) side | 1/4 in (6 mm), about one third | The real thickness of the shelf |
| Groove for a 1/4 in back or bottom | 1/4–3/8 in (6–10 mm) | 1/4 in, or the real panel thickness |
| Rabbet for a 1/4 in back | 3/8 in (10 mm) | 1/4 in plus 1/32 in clearance |
| Rabbet for a box corner | Half to two thirds of the thickness | The thickness of the mating board |
Measure the board, not the label: 3/4 in plywood is usually 23/32 in (18.3 mm), and 18 mm board is 0.709 in. A dado that is too wide leaves a sloppy, weak joint; too narrow and the shelf will not go in.
Remember the dadoes when you size the parts: a shelf that sits 1/4 in deep in a dado on each side is 1/2 in longer than the space between the sides.
How to cut a dado or rabbet
- Table saw with a dado stack: set the stack and shims to the board thickness and the height to the depth, and run the board against the fence. Fast and repeatable for many identical cuts.
- Router with a straight bit: clamp a straightedge guide and rout in passes no deeper than 1/4 in. A plywood-size bit (23/32 in) cuts the exact width in one pass; otherwise make two passes with a narrower bit.
- Circular saw: set the depth, cut both shoulders along a guide, then make several cuts between them and clean out the waste with a chisel.
- Rabbets on a table saw: two cuts at right angles with a standard blade, or one pass with a dado stack buried in a sacrificial fence.
Dado or shelf pins?
A dadoed shelf is fixed, stiffens the case and carries heavy loads; shelf pins let you move shelves. Many bookcases use both: one fixed shelf in dadoes in the middle to stiffen the sides, and adjustable shelves on pins above and below. Either way, check how far the shelves can span:
Frequently asked questions
What is a dado joint?
A flat-bottomed channel cut across the face of a board, into which another board fits. It is the classic joint for shelves and cabinet bottoms, because the shelf rests on the shoulder of the channel.
What is a rabbet joint?
A step cut along the edge or end of a board, open on one side, so another board fits into the corner. It is used for cabinet backs, box corners and drawer fronts.
What is the difference between a dado and a rabbet?
A dado has two walls and sits in the middle of the board; a rabbet has one wall and sits at the edge. A groove is a dado that runs along the grain instead of across it.
How deep should a dado be in 3/4 plywood?
About one third of the thickness: 1/4 in (6 mm) in 3/4 in plywood. Deeper weakens the side; shallower gives less support.
How do I cut a dado for undersized plywood?
Use an undersize plywood router bit (23/32 in), or a narrower bit in two passes, or a dado stack with shims set to the real thickness of your sheet.