There are many popular woodworking joints. A Woodworking joint’s strength varies, and some are better than others. Which ones are best for your projects?
1. Butt Joint
The Butt Joint joins two pieces of wood by merely butting them together. The butt joint is the simplest to make. It is the weakest joint, and you must use some type of reinforcement. You have an end grain to long grain gluing surface. The resulting joint is naturally weak. It relies on glue to hold it together; however, glue does not have much lateral strength. You can break this joint with your bare hands.
2. Biscuit Joint
A biscuit joint is nothing more than a reinforced Butt joint. The biscuit is an oval-shaped piece and is made of dried and compressed wood, such as beech. You install it in matching mortises in both pieces of the joint. Most people use a biscuit joiner to make the mortises. You design the biscuit joint to allow flexibility in glue-up. However, you must locate the mortise the correct distance from the face of the joint in both pieces. Since the biscuit is thin, you can move the alignment around. This is the very reason that I do NOT like this joint. It is not in perfect alignment. In addition, you waste your money on the Biscuit Joiner and a lot of time cutting the mortises in each piece of stock. Why bother?
3. Bridle Joint
A bridle joint is similar to a mortise and tenon. You cut a tenon on the end of one piece and a full width mortise into the other piece to accept it. This is the distinguishing feature of this joint You have only three gluing surfaces.
The corner bridle joint joins two pieces at their ends, forming a corner. You use this joint to house a rail in uprights, such as legs. It provides good strength in compression and is fairly resistant to racking. You must use a mechanical fastener or pin.
4. Dado (joinery)
A dado is a slot cut into the surface of a piece of wood. When viewed in cross-section, a dado has three sides. You cut a dado perpendicular to the grain. It is different from a groove, which you cut parallel to the grain. A through dado passes all the way through the surface and its ends are open. A stopped dado has one or both of the ends stop before meeting the edge of the surface. You use dadoes to attach shelves to a bookcase carcass. You rabbet the shelves to fit the dado, which makes the rabbet and dado joint.
5. Dovetail Joint
The dovetail joint, or simply dovetail, is a strong woodworking joint, and is great for tensile strength (resistance from pulling apart). The dovetail joint is used to connect the sides of a drawer to the front. A series of pins cut to extend from the end of one board interlock with a series of tails cut into the end of another board. The pins and tails have a trapezoidal shape. Once glued, the joint is permanent, and requires no mechanical fasteners. Some people use a dovetailed dado, because of the tensile strength.
6. Finger joint
A finger joint or box joint is used to join two pieces of wood at right angles to each other. It is similar to a dovetail joint except that the pins are square and not angled. The joint relies on glue to hold together. It does not have the mechanical strength of a dovetail.
7. Lap joint
A half lap joint is made by removing material from each piece so that the resulting joint is the thickness of the thickest piece. Generally, the pieces are of the same thickness. You remove half the thickness of each. This joint is good for making workshop storage items.
8. Mortise and Tenon
One of the strongest woodworking joints is the mortise and tenon joint. This joint is simple and strong. Woodworkers have used it for many years. Normally you use it to join two pieces of wood at 90-degrees. A mortise is a cavity cut into a piece of wood to receive a tenon. A tenon is a projection on the end of a piece of wood to insert into a mortise. You insert one end of a piece into a hole in the other piece. A quality mortise and tenon joint gives perfect registration of the two pieces. This is important when building heirloom pieces.
9. Pocket-Hole Joinery
The Pocket-Hole Joint is nothing more than a Butt joint with Pocket Hole Screws. The pocket holes require two drilling operations. The first is to counterbore the pocket hole itself, which takes the screw head. The second step is to drill a pilot hole whose centerline is the same as the pocket hole. Most people use a pocket-hole jig, such as the Kreg Jig(TM). This jig allows you to drill pocket holes at the correct angle and to the correct depth. Glue should be used to strengthen the joint. Of course, the Kreg Jig(TM) costs from $40 up to $140. To me, that is a lot of money when you can make the mortise & tenon jigs for a fraction of that price. Moreover, the mortise and tenon joint is much stronger.
A rabbet is a recess cut into the edge of a piece of wood. When viewed in cross-section, a rabbet is two-sided and open to the end of the surface. An example of the use of a rabbet is in the back edge of a cabinet. The rabbet allows the back to fit flush with the sides. Another example is the insertion of a glass pane by using a rabbet around the edge of the frame.
11. Tongue and Groove
Tongue and groove is made by cutting a slot (groove) along one edge. The other piece has a tongue cut on the mating edge. As a result, two or more pieces fit together closely. You can use it to make wide tabletops out of solid wood. Some other uses are in wood flooring, parquetry, paneling, etc.
Woodworking Joints Torture Test – Wood Magazine Nov 2006
Are pocket screws stronger than dowels? Which of the woodworking joints give the most strength? Do screws add any strength to a joint?
For the “Wood Joint Torture Test” in WOOD Magazine issue #173, they created and then destroyed more than 100 joints.
Wood Magazine Shear test:
Mortise & Tenon Joint took 1,005 lbs/force, which is over two to three times the force to break compared to other joints.
Wood Magazine Pull Apart test
The breaking force for a Biscuit miter joint is 220 lbs/force; Dado 559 lbs/force and screws did not help.
For a Mortise & Tenon Joint, the wood failed but not the joint. It took 4,733 lbs/force nearly 2½ tons to pull apart.
Clearly, this test shows that the Mortise & Tenon joint is superior to other joints.
For more information on Woodworking Joints, including pictures and the video by WOOD Magazine showing the results of these tests, please visit https://www.provenwoodworking.com/woodworking-joints.html
Copyright 2009 – Jim McCleary of provenwoodworking.com. All Rights Reserved Worldwide. Reprint Rights: You may reprint this article as long as you leave all of the links active, do not edit the article in any way, and give author name credit.