Kevin O’Connor meets general contractor Tom Silva in the shop for a lesson on wood joints. With several power tools and jigs on the table, Tom explains how joinery works and some of the most popular methods. He teaches Kevin everything from mitered and lapped joints to dowels, biscuits, floating tenons, and pocket hole joinery, with examples of each type to show how they work.
Different Types of Wood Joints
When it comes to joining two or more pieces of wood together, there are a ton of different methods. Some include specific cuts, like miters or half-laps, while others involve mechanical fasteners like screws or nails. They all vary in the amount of time, effort, and accuracy they require, so knowing as much about them as possible is worth knowing.
Butt joints are when two pieces of wood “butt” up to each other, whether at a miter or simply a right angle. By themselves, butt joints aren’t very strong, and since they often involve end grain, they don’t glue up nicely. However, they’re fast and easy to make, and they get much stronger when a mechanical fastener like a screw or nail holds them together.
Butt joints are common for simple storage boxes, utility shelving, or trim work where nailing the wall holds the joint tight.
Technically a butt joint, a miter joint is an angled cut between two pieces of wood. The most common example is window and door trim, with 45-degree cuts on the ends of each board, creating a 90-degree angle when assembled. While this does provide more gluing area than a butt joint, it gets much stronger when assembled with biscuits or floating tenons.
A half lap joint is a joint that involves removing half the thicknesses of two pieces of wood with a router or table saw and then overlapping them, achieving a consistent thickness at the joint. This joint provides a lot of gluing surface, and that gluing surface is mostly long-grain, making it much stronger than a standard butt joint.
Dado and Rabbet Joints
Another joinery technique for cabinets and drawers involves cutting a dado (a long groove) and then rabbet (a stepped recess along the end of a board that forms a tongue). The tongue of the rabbet slides snuggly into the dado, creating a sturdy and stable joint. This joint provides a lot of gluing surface, but finish nails can reinforce the joint even more.
Box joints are some of the oldest forms of joinery, and they’re made up of a series of small, square recesses and fingers. These recesses and fingers mesh together to create a very strong and stable joint with lots of gluing area (triple the surface area of a standard butt joint). A few finish nails can strengthen it even more.
While cutting the wood to increase glue area is an effective way to strengthen joints, mechanical fasteners can also help. These include dowels, biscuits, floating tenons, and pocket hole screws.
Dowels help strengthen a joint by increasing the gluing area while also bridging the joint. The holes for dowels are challenging to drill by hand, but special power tools make the job easier.
Mortise and tenon joinery is popular in traditional woodworking as the joints are strong and stable. However, they’re difficult to cut. With floating tenons, the user can cut a mortise in both sides of a joint with a power tool, insert a tenon inside, and then glue the joint.
A biscuit joint is a form of floating tenon that can increase the strength of a box, miter, or another style of joint tremendously. The biscuit is football-shaped and fits into a slot cut into both sides of a joint with a biscuit cutter. The increased gluing surface and mechanical bridge between both sides help assemble and lock the joint in place once dry.
Pocket Hole Joinery
While driving a nail or two through a joint is the simplest form of mechanical fastener, they’re often not very strong. Pocket hole joinery increases the strength with marginally more effort. By using a jig and a specialized drill bit, the user can cut a pocket hole for a screw, which passes through the hole and into the other side of the joint.
Tom explained how to identify different types of wood joinery and why they’re used in woodworking.
- Half-lap joint—Formed by creating two rabbet cuts, which requires cutting half of the end of the board. DOMINO DF Q-Plus by Festool.
- Half-lap butt joint—Formed by creating one rabbet cut, as explained above, and then placing the other board into the opening created by the rabbet cut. Hoffman—PDS 32.
- Miter Joint—Formed by creating two, opposing, 45-degree angle cuts on the ends of the board and then bringing them together, creating a 90-degree angle. Cut created using a Zeta P2 made by Lamello.
- Floating tenon joint (aka biscuit joint)—Formed using a biscuit joiner, a specialty tool that drills mortises wide enough to accept biscuits or tenons that are pre-cut and connect two boards with mortises together. Cut created using biscuit joiner, Top 10 by Lamello.
- Box joint—Formed by creating a series of cuts on each end of the board that create a castle or finger-shaped look. Cut created using Kreg Jig® K5.