Joinery Overview - Canadian Woodworking Magazine

Wood Joints: Joints are a fundamental part of woodworking. They have the practical function of joining pieces of wood together into a finished project while they can also provide a decorative element to your work.

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Joinery Overview



This is the first of a series on Joints. Subsequent articles will focus on specific joints, highlighting their key features, uses, and how to make them.
 
There are a wide variety of different joints, from traditional (i.e. dovetails and mortise and tenons) to modern (i.e. biscuit, dowels, and pocket hole joints).

Some joints can be made by hand in the traditional way, while others need power tools or special jigs. This wide variety of options allows you to select the joinery that is best for your particular project; the tools you have, your skill level, and how much time you want to spend making joints.

Some joints have a variety of applications, while others are used for very specific purposes. The best joint to use in a particular application will depend on several factors, including whether you want the joint to be visible or not, the types of forces the joint will encounter, and the nature of the joint. Many joints can be made in various forms, depending on your needs. Butt joints, for instance, can be screwed together, joined with pocket-holes, dowels, or biscuits. Mortise and tenon joints can be made in a variety of forms, including simple, loose, round, haunched, angled, and multiple tenon.

Dovetails can be through or half-blind, depending on what they are for, and the degree to which you want them to be visible. Joints that are specifically used for their visual appeal include dovetails, box joints, keyed mitres, and through mortises. Other joints are generally hidden, such as mortise and tenon, mitre, and butt joints. Joints are typically used for specific purposes, and can be generally divided into two basic categories (with some joints found in both categories). One type joins long edges together, such as the sides of a blanket chest. Such joints include rabbets, dados, splines, finger joints, and dovetails.

The second type joins narrower edges together and includes lap joints and bridle joints. Some joints are used for both types, including the mortise and tenon, mitre joints, and butt joints.

The strength of a joint depends on how much cross grain is glued together in the joint. That is why a butt joint generally needs screws, splines, biscuits, or dowels to add strength. With a butt joint,at least one surface is end grain and, therefore, they provide a very weak joint. On the other hand, joints such as finger joints, dovetails, and mortise and tenons provide lots of cross grain surfaces to be glued together.
 

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Mortise and tenon
 
That makes a very strong joint, without the need for mechanical fasteners, splines, or other means of adding cross grain surfaces. In order to be strong and to look good, a certain amount of accuracy is needed when making joints. You need a snug fit that will avoid gaps.

At the same time the joint must not be so tight that the joint is starved of glue. If you are using power tools to make your joints, use jigs where possible, to ensure accuracy and repeatability. Also, use a scrap piece of wood to set-up the tools and jig. That will ensure the best fit before cutting your project pieces.

Hand made joints simply require patience and practice. Before cutting dovetails on your blanket chest, practice on some scrap pieces until you get it right. When working on your project pieces, take it slowly and sneak-up on the correct size. It also helps to test the fit regularly. You can always trim a little more wood from the joint to get the best fit, but you can't add it back.

Since joints are an important part of woodworking, don't shy away from tackling projects that use joints you think are beyond your ability. Even if you don't feel comfortable making some of the classic joints by hand, most of them can be made with power tools and home made jigs. A little practice and patience, and you will soon be able to make every joint you need.

Watch for future articles in this series. In them, Michel will focus on a different joint each issue. He will explain the joint in detail, and give instructions on how to make each one. Future joints will include: dovetails, dowels, mortise and tenon, mitre joints, drawer lock joint, butterfly key, tongue and groove, frame and panel, lap joints, finger jointsstopped dado joints, butt joints, and wedge joints.



MICHEL THERIAULT is a writer and woodworker living in Guelph, ON.
Michel Theriault