How to Make Common Woodworking Joints
You can have a more finished and professional look to your work by using joints instead of screws and nails. Here are some of the basic joints used in woodworking.
The butt joint is the simplest of the woodworking joints and is very easy for beginners to master. The joint consists of two board ends that are pushed, or butted, together and held with nails, screws or glue. Simple wood boxes are often constructed with butt joints. While the butt joint offers a quick finish, it does not offer structural strength in most cases. If a butt joint held together with nails is required to bear much weight, the nails may soon pull out of the wood. For beginners, though, the butt joint offers an easy way to complete a project without expensive equipment or in-depth woodworking knowledge.
Square-ended butt joints –
It is possible to make flat frames and simple box structures utilizing square-cut corner joints. Use sawn wood for rough carpentry, but plane the wood square beforehand for good-quality cabinet work. Since glue alone is rarely adequate to make a sturdy butt join, hold the parts together with fine nails or glued blocks of wood.
Mitered butt joint –
The classic joint for picture frames, the mitered butt joint makes a neat right-angle corner without visible end grain. Cutting wood at 45 degrees produces a relatively large surface area of weight frames, just add glue and set the join in a miter clamp for a while.
Edge-to-edge butt joint –
Lumber selection is as important as good edge-to-edge joints when making a wide panel from solid wood. To make sure the panel will remain flat; try to use quarter-sawn wood – that is, with the end-grain growth rings running perpendicular to the face side of each board. If that is not possible, arrange them so the direction of ring growth alternates from one board to the next. Also try to make sure the surface grain on the boards runs in the same direction, to facilitate the final cleaning up of the panel with a plane. Before you get to work, number each board and mark the face sides.
Tongue-and-groove joint –
Use a combination plane to cut a tongue-and-groove joint by hand. This kind of plane is similar to a standard plow plane but comes with a wider range of cutters, including one designed to shape a tongue on the edge of a workpiece. Cut the tongue first, then change the cutter and plane a matching groove.
This technique is ideal for joining two flat pieces together to form a larger flat surface.
Take two pieces of equal length wood. Decide now which side will be the top and which the bottom for each piece and mark the top side of each so that you do not forget.
Clamp both pieces together, one on top of the other, with the bottoms face to face in the middle. When clamping, ensure that the two surfaces along which you plan to join these pieces of wood are level with each other (see diagram one).
Draw a line down the middle of each surface to be joined. This must be exactly the same on both pieces of wood, otherwise when they are joined there will be a step at the join. Once this line has been drawn, use a set square and mark lines across the grain of the wood. The intersection of the length and width lines will show where the dowel holes will be drawn.
There is no hard and fast rule for how many dowels should be used. However, the heavier the weight of whatever will be on the surface, the more dowels should be used. Typically, one dowel per foot is a good rule (with a minimum of two).
Once these lines have been drawn you can then proceed to drill the holes at the marked intersections. The drill bit used should match the diameter of the dowel being used, thus ensuring a tight fit.
As for the dowel itself, you can either make your own small dowels from a longer length, or you can buy dowel made specifically for this reason. The latter option is a far better solution, as the small dowels are beveled at the ends to make it easier to but them in the holes, and are ribbed to allow the glue to bond more efficiently. Each hole should be just over half as deep as the length of the dowel being used.
Once the holes have been drilled, glue one end of each dowel into the holes in the first piece of wood. Then place glue along the full length of the second piece, ensuring that some glue falls into each of the holes.
Unclamp the two pieces and push them together, ensuring that the two top markings are facing up. Once done you should clamp tightly overnight. Be careful when you clamp them to make sure that both pieces remain flat and do not try and warp upwards. To avoid this, it may be necessary to clamp the entire piece down to a flat surface.
Doweled frame joints –
Frames made with doweled butt joints are surprisingly strong. Nowadays, most factory-made furniture incorporates dowel joints even for chair rails, which must be capable of resisting prolonged and considerable strain. In most cases, two dowels per joint are sufficient. Place them a minimum of ¼ inch from both edges of the rail.
Edge-to-edge dowel joint –
When constructing a wide solid-wood panel, you can make a particularly strong join between boards by inserting a dowel every 9 to 12 inches.
Carcass butt joints –
When constructing a carcass with butt joints that are reinforced with multiple dowels, it pays to buy extra-long slide rods and additional drill bit guides for the doweling jig. A doweling jig is required for many of the dowel joints. This can be an expensive piece of machinery and if you are not going to use it very often, it might be worth looking into renting one or borrowing one from someone.
Corner bridle joint –
A corner bridle joint is adequate for relatively lightweight frames, provided they are not subjected to sideways pressure, which tends to force bridle joints out of square. The strength of the bridle is improved considerably if you insert two dowels through the side of the joint after the glue has set.
Mitered bridle joint –
The mitered bridle is cut in a similar fashion as the conventional corner joint, but is a more attractive alternative for framing, because end grain appears on one edge only.
T-bridle joint –
The T-bridle joint serves as an intermediate support for a frame and with modifications, is sometimes used to join a table leg to the underframe when a long rail requires support. Unlike the corner bridle, which is relatively weak under sideways pressure, the t-bridle is similar in strength to the mortise-and-tenon joint.
Lap joint –
A basic lap joint is only marginally stronger than a straightforward butt joint, but it is an improvement in appearance since most of the end grain is concealed. As a result, it is sometimes used as a relatively simple way of connecting a drawer front to drawer sides.
The dovetail joint is possibly the best joint that you can use to join two pieces of wood together at a right angle. Not only is it a very strong joint, but it also adds to the appeal of the woodworking project.
The simplest way to create dovetail joints is to use a router and a dovetail template jig.
Arrange the three pieces of the drawer or box as shown in the first diagram and mark the inside and outside of each piece. In addition, mark the ends of each piece as it is imperative that when cutting the dovetails the correct two ends are cut at one go.
Clamp the front of the drawer and one side into the dovetail machine as follows: the left side of the drawer should be clamped under the front clamp (pointing upwards towards the template) with the inside of the drawer pointing out; the front of the drawer – again with the inside pointing out -should be clamped under the top clamp so that it butts up against the left drawer.
These two pieces should be staggered slightly, rather than being aligned exactly. The precise measurement will depend upon the particular dovetail machine that you are using, and this distance will be supplied with its manual. However, it should be roughly in the region of 7/16 inch.
Once everything is tightly clamped in place, use the router to cut around the template, following the direction of the arrows in this diagram.
You can then join the boards together at the joints securing with glue and clamping overnight.
It is well worth practicing with scrap wood before trying the above procedure on any project as it will take a while to get the exact measurements (such as the depth of the router cut) perfect.
If the joint is too loose, slightly increase the depth of the router cut. If the joint is too tight (remember that you still have to squeeze some glue into the joint), slightly decrease the depth of the cut.
Through mortise and tenon joint –
The through joint, where the tenon passes right through the leg, is used a great deal for construction frames of all kinds. With the end grain showing, possibly with wooden wedges used to spread the tenon, it is an attractive businesslike joint. Always cut the mortise first, since it is easier to make the tenon fit exactly than the other way around.
Slotted Tenon Joints
Slotted tenon joints are typically used as a method of fixing shelving into a unit’s shelf walls. However, it can also be used for a number of other purposes.
The idea of a slotted tenon joint is that only one of the two pieces of wood needs to be modified in order to attain a good, tight fit. To do this, one piece has a slot made into it that is the same width as the thickness of the second piece of wood. This latter piece of wood can then be pushed into the groove, making a strong, right-angled join.
The most effective way of creating the groove (or slot) is to use a router. Although a chisel can be used, the quality of finish will not be the same (and it takes far longer to make).
Be careful when making the slot to ensure that it is not too wide, otherwise the joint will not be tight enough to work. It is far better to start with too tight a groove and then widen it.
A router is not always the best tool to use, however. If the groove is to hold a piece of 1/4 inch (or smaller) plywood, you should use a circular saw instead, changing the depth of cut to as little as 1/4 inch. This smaller cut is ideal when making the joint for a back panel of a cabinet, such as a bedside cabinet.