Wood Joinery Basics
You don't have to be a pro to make wood projects that stay together, but a solid knowledge of wood joinery basics definitely helps.
When you construct anything with wood, you’re confronted with the problem of how to make two pieces stay together. This is called joinery, and in woodworking traditions it’s a specialized trade. Masters of joinery have developed ingenious ways to assemble pieces of wood, with perhaps the most legendary examples coming from Japan.
In the 10 years I spent there I often visited the Horyuji Temple in Nara, the world’s oldest wooden building, built without a single nail. During that time I worked with a German carpenter practicing Japanese joinery. Let’s just say that, as a woodworker who focuses mostly on utilitarian projects, I decided the required precision and patience were not for me.
However, that doesn’t mean I do all my wood joinery with glue, screws and nails. Many joining techniques call for cutting, shaping, digging and boring. But modern woodworkers — especially those on the clock — do this with power tools rather than chisels, mallets and hand saws.
If you’re starting out in woodworking, you don’t need to know how to make the most elegant joints unless that’s your specific interest. But you do need to know how to make some basic ones so your projects don’t fall apart.
What Is Wood Joinery?
It’s the art and craft of assembling wood to form a structure. Some types of wood joinery are necessary for any woodworking project that involves more than one piece of wood, so every woodworker needs to understand and use joinery techniques.
You can join pieces of wood in a straight line or at an angle, with 90 degrees the most common angle. Joinery is needed to construct tables, chairs, cabinets and drawers, as well as buildings and other large projects.
Many joints rely on fasteners to hold them together, but some of the more elegant ones work without them. The latter, as you might expect, call for more effort and a higher level of precision.
Wood Joinery Tools
These range from simple hand tools that have been around for centuries to modern power tools. The hand joinery tools you’ll find in a typical wood shop include:
- Chisels: Used to cut and pare shapes for joining. There are many types. Some, like mortise chisels, create specific types of joints.
- Mallets: Used to strike the chisels. They’re usually made of wood to prevent damage to the chisel handles.
- Hand planes: These shave wood to the precise dimensions needed for a tight joint.
- Hand saws: Precision tools. Japanese hand saws, which are widely available in North America, have thin blades and ultra-sharp teeth that cut on the pull stroke. Dovetail and back saws are other types used in joinery.
Most of the power tools you find in a wood shop have joinery applications, and some are intended just for joinery:
- A power saw: A table, miter or circular saw shapes wood and cuts grooves for various types of joints.
- A router: Another groove-cutting tool that also shape wood and digs holes.
- A jointer: A power planer that makes the perfectly flat, clean edge you need for lamination, the process of butting and gluing panels or pieces of wood together.
- A biscuit joiner: Cuts a precise groove for a biscuit, an oval-shaped spline used with glue to make a hidden butt or corner joint.
- A dowel jig: Used with a drill or drill press, positions dowel holes precisely on the ends or edges of wood. This way you can make hidden joints with cylindrical wooden dowels.
- Clamps: Hold glued joints together until the glue sets. A typical wood shop needs a collection of bar clamps, C-clamps and spring clamps.
A master craftsperson may also have tools for making specialized joints. These include jigs and saws for dovetail and finger joints, which make super-strong and elegant joints for drawers and cabinets. All of these take years to master.
Wood Joinery Methods
Joinery methods don’t always have names, at least not in English. Fortunately, the methods you’ll need when starting out as a woodworker do. Here are some of the most common:
The simplest joint, these are formed by butting the end of a piece of wood or wood panel against the end or side of another one. Butt joints usually need reinforcement from metal fasteners, dowels, splines or biscuits.
Dado and rabbet joints
A dado is a groove cut across the grain of a board or panel where the edge of another board or panel fits. A rabbet is a groove cut on the edge or end of the board, not in the middle.
You usually cut dadoes and rabbets with a router or a table saw and a dado blade. It’s typically formed by multiple regular blades stacked together. Tight-fitting dado joints are strong and sometimes hold with no fasteners besides glue. Rabbet joints aren’t as strong and usually need fasteners and glue.
This is a corner joint formed by notching two boards and overlapping one notch over the other. It’s stronger than a butt joint because it provides more area for gluing, but it usually needs fasteners or some other reinforcement.
A miter joint is also a corner joint. It’s similar to a butt joint, except the ends of the boards are cut at 45-degree angles. It’s slightly stronger than a butt joint and looks better. It’s also easier to reinforce with dowels, splines, nails, screws or corrugated fasteners.
A mortise is a hole or depression cut into a board, and a tenon is a shaped extrusion on the end of a second board that fits into it. Tight-fitting mortise-and-tenon joints usually need no glue or other reinforcement, but can be challenging to make. Japanese master joiners use this type of joint extensively.
Wood Joinery Tips
When you assemble a wood project, you need strong joints that also look good. Here are five tips for great joining:
- Check the wood: Try to avoid warps, cracks and splinters that will weaken the joint. Avoid green, unseasoned wood, because it will shrink as it dries out and weaken the joint.
- Use sharp blades: Keep chisels sharp and replace dull saw blades. Dull blades don’t make clean cuts and can chip the wood.
- Clean up glue while it’s wet: Glue will ooze from a joint when you clamp it. Clean it up immediately; it’s much more difficult to remove after it sets.
- Drill pilot holes: Any time you assemble a joint with screws, drill pilot holes for them. If you don’t, the wood may split and ruin your project.
- Measure twice, then once more: When joining with dowels, biscuits or splines, a slight offset can be disastrous. If you can’t use a jig, triple check your measurements.