After wood the most important factor that determines the quality of furniture is the quality of joints. Good joining can make even average quality wood last really long. On the other hand, the best quality oak could also be rendered useless due to loose fittings.
All furniture is put together in a series of joints. Most structural problems involve joint weakening or failure. The joints used in good wooden furniture, such as Amish furniture, are usually stronger than those in cheap pieces, but age and abuse can take their toll even when the original construction was good.
Knowing the various joints used on a piece of furniture will help you evaluate the quality of a furniture piece before purchase. If you are a DIY type, having the following information will also help you repair them. Furniture bought online should be inspected in detail on delivery. If you buy Amish furniture online, you can be sure of high quality craftsmanship.
Dovetail joints: Dovetail joints consist of wedge-shaped openings, the dovetails, holding matching pins cut in the joining piece. In this joint, the dovetail goes completely through both pieces of wood. The pins in handmade dovetails are usually narrower than the spaces between the pins. In the older days only a few dovetails were used and the tails and pins did not match exactly. With modern equipment, the tails and the pins are exactly the same size and more dovetails are used in each joint.
Mortise-and-tenon joints: In this type of joint, a prong or tongue of wood, the tenon, is secured in a hole, the mortise, in the joining piece. Mortise-and-tenon joints are extremely strong; they're used chiefly in chairs and tables.
Dado joints: A dado is a slot cut into the face or end of a piece of wood; the joining piece fits into this slot. In a simple dado joint, the slot goes completely across the wood, and the edges of the joining piece are visible along the edges of the base piece. Dadoes and stopped dadoes have considerable shear strength and are used chiefly for shelving.
Lapped joints: Lapped joints are cut with both joining pieces notched or slanted to the same depth. Lapped joints offer a large glue area, but they are not particularly strong. Cross-laps are used to join crossing pieces; half-laps and sloped laps are used to join the ends of long pieces. They're often used in drawer guide framing pieces and may be pinned with nails or screws from the back.
Butt joints: In this type of joint, the joining pieces are simply butted together with no integral fastener. Butt joints are weak and are sometimes fastened or held together with metal surface plates. They are used in chairs, tables, dressers, and cabinet pieces.
Miter joints: In a miter, the joining pieces are cut at a 45-degree angle and joined to form a right angle. Miters are used for decorative molding and for frames. They are very weak and are often reinforced with dowels, spline, or mechanical fasteners. Sometimes triangular glue blocks are used for strength; the blocks may be reinforced by screws.
Doweled joints: The doweled joint is a simple variation of the mortise-and-tenon joint, with dowels instead of a cut tenon holding the joining pieces together. Doweled joints require precision equipment. They are strong and are common in chairs, tables, and cabinets, usually on stretchers and other framing pieces.
Splined joints: In a splined joint, the edges of the joining pieces are grooved or dadoed to match each other and a reinforcing spline is inserted into the grooves to hold the pieces together. Splined joints are used chiefly to join narrow boards.
Rabbet joints: The rabbet is a reinforced butt joint, with one or both joining members notched to fit together. It is usually reinforced with screws or nails. Rabbet joints are easy to make and very strong. They are used chiefly for shelving and at the corners of cabinet pieces.
Drawer construction is generally a good indication of overall furniture quality. Doweled and dovetailed drawer joints indicate a high degree of craftsmanship. However, modern machine technology, good bonding glue and pneumatically driven staples coated with resin have afforded savings in construction while providing durability. The Amish craftsmen who make wholesale Amish furniture take very good care of the quality of the joints. Quality wood furniture purchased today can be used for a lifetime.