Antique Furniture Joints
Determine the quality of your antique furniture.
Recognizing different kinds of furniture joints can help you determine the quality of antique furniture. If you discover that a chair is constructed using mortise and tenon joints as opposed to dowel construction, for example, you can be sure it's a high quality chair. The same is true about furniture with dovetail construction on the drawers as opposed to rabbet joint drawers. Dovetails are a better joint and will last indefinitely.
A basic knowledge of antique furniture joints is also important in antique furniture repair for a number of reasons. If joints are loose on a piece of furniture, you'll probably have to disassemble the piece to reglue it. When you look at the exterior surface of a joint, you may only see a line where the two pieces of wood meet. Your knowledge of antique furniture joints can give you understanding of what's hidden below the surface of that line, enabling you to work the joint loose without breaking it. If you have a broken joint or pieces are missing, knowing the type of joint you're working with allows you to repair it properly.
A butt joint is made when two pieces of wood are butted together and glued. Boards are commonly joined end grain to edge grain, edge grain to edge grain, or edge grain to face grain, although other configurations are possible. When you glue an end-grain surface of one board to another wood surface, the joint won't hold unless it's reinforced with dowel pins or some other reinforcement. The reason for the reinforcement is that the end grain of wood doesn't provide enough solid surface for the bonding process to take place. When magnified, end grain looks much like the end of a group of drinking straws bunched together. Consequently, the open end of the grain fibers absorbs most of the glue you apply to the joint and doesn't leave enough on the surface to provide a good bond.
When you use the butt joint to glue two or more boards side by side, or edge grain to edge grain as when making a wide top for a table, however, the joint can be quite strong. You must make sure that the joining edges are planed smooth to form a perfect fit, though, and that the joint is glued and clamped sufficiently.
Lap joints are created when two pieces of wood overlap one another at a right angle. Usually at least one piece of wood is notched out, allowing the other piece to fit down into it. This kind of lap joint is called a full-lap joint. Both pieces may also be notched to half of their thickness, allowing them to fit into each other. These lap joints are known as half-lap joints.
The miter joint is formed by cutting corresponding angles, usually 45 degrees, on the ends of two pieces of wood and joining them together. The most common use of the miter joint in furniture is in mirror and picture frames. The miter joint may be reinforced with pins or dowels or with the installation of a wooden back panel, often 1/4-inch plywood.
When you notch the end or the edge of a piece of wood and use that notch to join two boards, you've created a rabbet joint. You can also make a rabbet joint by notching both pieces of wood. The rabbet joint is not a strong joint in itself and is usually secured with fasteners like nails or screws. Sometimes drawer sides are joined to the fronts with rabbet joints. Rabbet antique furniture joints are used in casework furniture like chests or in some drawers to join the sides to the front and/or back. Cabinet backs can also be joined to the case with rabbet joints.
A dado is a groove cut across the grain of a piece of wood. A dado joint is formed by cutting a dado in one piece of wood the exact size as the square-cut edge of another piece. The square-cut edge of the second piece is then inserted into the groove of the first piece to form a tight, secure joint. This type of joint is also usually glued. Dado joints are commonly used to join wood at right angles, as in bookcase shelves. Sometimes the dado is hidden because the groove is not cut all the way across the board to the front of the bookcase. This kind of dado joint is called a blind dado.
Mortise and Tenon Joint
The mortise and tenon joint is one of the strongest antique furniture joints, and its use usually signifies quality furniture. The mortise and tenon joint is normally formed by cutting a square tongue (the tenon) on the end of one piece of wood and an equal size square hole or slot (the mortise) in another. The tongue of the first piece is then inserted into the slot of the second. Although not necessary, sometimes a pin or peg is also inserted through the joint, perpendicular to the tenon, locking the joint together. Mortise and tenon joints have been used not only in furniture but in the construction of centuries old wooden bridges, barns, and houses. Many of these structures still stand today, a testimony to the strength and stability of the mortise and tenon joint.
Dowel joints are basically substitutes for mortise and tenon joints. Many modern pieces, particularly chairs, are constructed using dowel joints. A dowel joint is made by fitting a butt joint and then drilling corresponding holes in the two pieces of wood to be joined and inserting the dowel pin or pins before joining the pieces. Glue is used in this type of joint, and the dowel pins serve as round tenons, holding the two pieces together. Although dowel antique furniture joints are commonly used and are easier to make than a mortise and tenon joint, they usually aren't as strong.
The dovetail joint is one of the most distinctive and best antique furniture joints used in furniture construction to join wood at a right angle. Easily distinguishable by its multiple flared tenons, which interlock like fingers and look like doves' tails, the dovetail forms a strong, durable joint. Most commonly used to attach drawer sides to drawer fronts, dovetails joints almost always indicate quality furniture. Antique and handmade furniture were built using hand-cut dovetails created with fine-toothed saws and chisels. Modern manufactured dovetails joints are cut by machine and are usually distinguishable from the hand-cut type because the interlocking flared tenons, called pins or tails, are exactly the same size and are evenly spaced. Hand-cut dovetail antique furniture joints usually have tails that differ slightly in size and may vary in spacing. Machine-cut dovetails joints are excellent, strong joints, but the old hand-cut variety is still hard to beat.
Dovetail joints can be constructed using either "through" dovetails or "half-blind" dovetails. Through dovetails are cut all the way through the thickness of both joining pieces of wood, with the "fingers" visible from two sides. Half-blind dovetails are cut so that the dovetails are visible only from one side. An example of a half-blind dovetail joint would be where a drawer side is joined to a drawer front with dovetails that are not visible on the face of the drawer front.