Wood Joints

The language of the joiner is filled with words that we know well from ordinary usage but here have new and distinct meanings: Lap, edge, butt, and finger joints are technical terms to woodworkers. Joinery jargon gets still more compli­cated when you add in some other kinds of joints, like mortise-and-tenon, tongue-and-groove, dovetail, dowel, dado, spline, and rabbet. Not to men­tion such combination joints as cross laps, dado rabbets, dove­tail laps, and keyed miters.

Yet this is, to say the least, a rather incomplete list of wood joints. With the introduction of the biscuit or plate joiner, any number of these joints are strengthened or varied thanks to the presence of the little, football-shaped wafers.

Don't be intimidated by all these possibilities. Try thinking of them as an embarrassment of riches. Pretty soon you will find that it's fun to figure out which will work best for a given project or a particular application.

If you are just making your first foray into the land of the join­ers, you'd probably do best to start with a simple joint like a dado or a rabbet. (If you've ever made anything, you've al­most certainly made a butt joint already.) A picture frame typically uses a miter joint, so perhaps you've done that, or would like to try.

So here they are, the basic kinds of wood joints, in some­thing approaching simplest-to-hardest order.

Butt Joint. When you join two squared-off pieces of wood, you've made a butt joint, whether the workpieces are joined edge to edge, face to face, edge to face, or at a cor­ner. A butt joint is the simplest to make, requiring little shap­ing beyond cuts made to trim the workpiece to size. As with all joints, however, the surfaces to be joined must fit together tightly; if they don't, a block plane may be used to smooth the end grain. Glues, nails, screws, dowels, and other fas­teners may be used to secure a butt joint.

Miter Joint. As you know from the miter box and the miter gauge on your table saw, a mi­ter cut is basically an angle cut (though if you consult your dic­tionary, you'll get told some­thing like, "A miter is an oblique surface shaped on a piece of wood or other mate­rial so as to butt against an oblique surface on another piece to be joined with it.").

To put it another way, a miter joint is a butt joint that con­nects the angled ends of two pieces of stock. The classic ex­ample is a picture frame, with its four butt joints, one at each corner, with the ends of all the pieces cut at a forty-five-degree angle, typically in a miter box.

The miter joint has two signal advantages over a butt-corner joint: First, no end grain shows, making for a more regular and attractive joint; second, the sur­face for gluing is increased. Mi­ter joints may also be fastened with nails, screws, dowels, or other mechanical fasteners.

Rabbet Joint. A rabbet (or re­bate, as it is also known) is a lip or channel cut from the edge of a workpiece. A typical rabbet joint is one in which a second piece is joined to the first by setting its end grain into the rabbet. Rabbet joints are frequently used to recess cabinet backs into the sides, or to reduce the amount of end grain visible at a corner.
The rabbet joint is much stronger than a simple butt joint, and is easily made either with two table or radial-arm saw cuts (one into the face, the second into the edge or end grain) or with one pass through a saw equipped with a dado head. A router or any one of several tradi­tional hand planes, including a plow plane, will also cut a rab­bet. Glue and nails or screws are frequently used to fasten rabbet joints.

Dado Joint. When a channel or groove is cut in a piece away from the edge, it's called a dado; when a second piece set snugly into it is joined to the first with nails, glue, or other fasteners, a dado or groove joint is formed. Some cabinetmakers differentiate between groove and dado joints, insisting that grooves are cut with the grain, dadoes across. Whatever you want to call them, grooves or dadoes are cut easily with a dado head on a radial arm or table saw.

The dado joint is perfect for setting bookshelves into uprights, and can be fastened with glue and other fasteners.