A wood jointer is power tool used by woodworkers to square and true boards. In other words, it will make a board straight and its edges will be at perfect right angles to its top and bottom faces.
The jointer is a high-speed, stationary power tool. It has a table consisting of two adjustable surfaces: an infeed and an outfeed. Between these two horizontal surfaces (under a safety guard) is an opening below which are razor-sharp knives that rotate at a high speed. By adjusting the height of the infeed surface the knives will shave wood away from a board fed through the jointer.
An adjustable fence lies at right angles to the table surface. This allows the adjustment of the width of the table to the width of a board being shaved by the blades. A 6-inch jointer can only plane board widths up to 6 inches. An 8-inch Jointer can plane up to 8 inches, etc.
Why the need for a jointer?
If you were to look at a piece of fine furniture made out of individual pieces of wood, you would probably see a board on the left side is the same size as the corresponding board on the right side. A board on the top is the same size as a board on the bottom, etc! Many pieces of furniture have to maintain a symmetry – in other words, what’s on one side has to look the same on the other side of the piece does not look right.
Wide, Flat Surfaces
Originally jointers were used for the following purpose. Often woodworking projects require a flat surface that is wider than one board width. For example, say you are building a table. Here you might need a width of 42 inches (about 100 cm) or more. This can be accomplished by clamping and gluing four or more boards side by side.
It would seem that here the problem is solved. And with luck, sometimes it is. But most of the time when you put the edges of four or five boards together, you will find gaps between them. And it can be quite frustrating when you carefully handpicked the boards, to begin with. Gluing and tightly clamping the boards might remove the spaces if you are lucky. Or, if you have a lot of time, you can select more boards and lay them side by side until you eventually find boards that do fit together tightly. As explained below, a jointer can easily solve this problem.
Kiln drying and/or aging of lumber can cause the edges to become malformed. The board might be crooked or twisted or both. And when these boards are laid side by side they can have gaps.
Gaps might not be a problem in building homes or in some woodworking projects, but in trying to produce two or more boards of equal widths with perfectly straight and square edges, a lot of new lumber must be reworked.
Removal of Board Imperfections
Edge imperfections can be removed with a hand plane, a carpenter’s eye, and a lot of patience or a jointer. In the past, carpenters used hand planes and planned along the length of the board to remove the crooks. First, you need to identify where the problem areas are. This can be done by laying a stiff measuring tape along the length from end to end and marking the areas that need to be shaved down. Then you begin planning and laying a flat edge next to the board and you will slowly see the gap disappear. Obviously, this requires a lot of patience and time.
A wood jointer can remove these imperfections very quickly usually in less than a minute if not seconds. Then when a piece of lumber is laid next to another piece they fit together smoothly and precisely. A tight ‘joint’ is formed. Hence the origin of the word ‘jointer’ a tool that can form a tight joint! The carpenters of old could only marvel at what a modern wood jointer can do in a few seconds!