Almost any woodworking project will require some type of wood joint. From building beds to bookcases and just about everything in between, you will find that wood joints will be necessary. While there are many styles and even variations of each style, there are 6 basic wood joints that can be used for all your building needs.
The Butt Joint
This is the simplest of all wood joints and is used more heavily in construction projects as opposed to furniture woodworking. A butt joint uses nails or screws to butt two pieces of wood together. To create this joint, no cutting or routing is required to interlock the pieces of wood. First you should use a carpenter's square to be sure that the two pieces of wood are level and perpendicular to each other. It is always best to use a small amount of adhesive along with the nails or screws. If you need additional strength, use corner brackets of angle irons if they will be hidden from view.
If you want to hide the ends of the pieces of wood, a miter joint is the way to go. This is a weaker joint and is normally used for decorative pieces such as molding, trim or frames. If you are working on a joint that requires support, stay away from this wood joint. The most common use of the miter joint is to attach two pieces of wood at a 90 degree angle. For the best results, use a circular saw and set the angle to 45 degrees. After your pieces are cut, add some adhesive and nail the pieces together. Be careful to position the nail so that it does not come too too close to the edge of either piece and split the wood.
If you need a strong wood joint, but the pieces of wood you are joining are different thicknesses, the lap joint is the answer. Quite simply, a lap joint requires notching of both boards. There are several types of lap joints that can be used depending on the location of the joint. If you are joining the ends of two pieces of wood, use an end lap. This requires that you saw out the end of each piece of wood the width of the adjoining board and one half the thickness of the board. When placed together you will have a strong, 90 degree joint. If you want to join the end of one board to a center section of another board, you can choose from a cross lap, middle lap or dovetail lap joint.
This joint combines the butt joint and the lap joint and is used if your woodworking project involves cabinet, bookcases or drawings. This joint is used to join the ends of two pieces of wood. To create this type of joint, cut or route a recess in one piece of wood that is the thickness of the adjoining piece and half the thickness of the board. After creating the recess, the second piece of wood will form a butt joint into the recess.
The dado joint is similar to the rabbet joint, but it is used to join the end of one piece of wood to a middle section of another. This joint is heavily used to interlock the ends of shelves to the side pieces when you are building bookcases or cabinets. For this joint you do not need to cut or route the shelves. At the desired location, cut or route a recess in the side board that is the thickness of the shelf, half way through the side board. This is a strong joint and will give full support to the shelves.
This type of joint is basically a butt joint that is reinforced by interlocking wood dowels between the boards. In order to achieve a square and level joint, it is crucial that the dowels from the first board are properly aligned with the second board. It is highly recommended that a doweling jig be used. Drill the holes in each piece of wood slightly deeper than one half of the length of the dowel. This will insure that the two pieces will fit flush and the dowel will be completely hidden.
Source by Alan J. Douglas