The Complete Illustrated Guide to Joinery
Step By Step Guide to Making Every Practical Type of Joint in Woodworking

	If you have two good mating edges, you can glue up the boards by just aligning them and rubbing their edges together.

If mortises and tenons represent most of the joinery available to a woodworker, edge joints make up the rest. Edge joinery relies mostly on adhesive strength, although there are exceptions. Unglued tongue-and-grooves or shiplapped boards can make up the back of a cabinet, and unglued coopered staves for a barrel can be held in place by an iron hoop. Some edge joints do have reinforcing, like biscuits, dowels, or even a tongue and groove. But these types of reinforcement are used as much for alignment as for strength. What edge joinery depends on is two good mating edges cut straight and true and bonded together with a good adhesive.

 

	Burned wood will not glue up well. Make sure your surfaces are always clean, straight, and without any twist.

Edge laminations put together with a good adhesive are so strong they are often stronger than the surrounding wood. But this strength depends heavily on the mating surfaces being true, clean, and without twist, so as the wood moves it does not put the edge joint under any additional strain. You can pull together any joint with enough clamping pressure, but the joints that will last are the ones require only moderate pressure to close.

Edge-joint uses
You can use edge joints to make simple laminations, construct coopered door shapes, or create wide panels from narrow widths. You can also construct tabletops, carcase sides, and the panels that fit into frames. Edge lamination is used to band the edges of plywood or other sheet-good materials with solid wood.

 

	To check for a spring joint, look for a little bit of light showing through the middle of the edges. The boards should also have some pressure at their ends when you try to spin one board on the other.

Spring joints
Edge joinery attempts to do a very basic and yet sometimes difficult task: mating two edges together completely along their entire length. Most boards flex enough even in their width to allow you to clamp out any gaps at the ends of a board. But consider that twice as much moisture loss and gain occurs out at the end of a board through the end grain.

If an edge lamination is going to fail, it will usually fail at the end of a board first. This is where a spring joint really shines. By planing in a small hollow along the length of the boards, you will need to apply pressure to close up the joint. This creates more pressure and a little bit of springback at the ends where the boards start to lose moisture first. Cut this hollow into both mating edges and then check for a sliver of light shining through the joint.


 

	Before jointing the edges, mark out the face sides and align the boards for looks or grain or both.

Edge gluing
Before doing any edge lamination, get in the habit of checking some details for the best results. Arrange the boards for grain direction before joining the edges. Some woodworkers alternate heart sides up or down to minimize cupping. Others run the boards consistently heart side up or down to yield a consistent cup. Still others just choose the best-looking combination of boards.

If you're going to handplane the faces after gluing, line up the grain for a consistent planing direction. Remember that there are eight possible ways to arrange two boards together for a simple edge lamination, so there are plenty of options.

Mark out the face sides and which edges will be glued together. Use flat pipe or bar clamps that you can register the boards on accurately. Have them resting on a good true surface. If the clamps and work surface are flat and you keep the boards flat on the clamps, your laminations have a much better chance of coming out flat as well.
 

	Dry-clamp the boards after planing them to make sure the joint closes up on both faces.

Plane the edges and then dry-clamp the boards together. This will make you get out all the clamps and tools you'll need for the glue-up before the glue starts drying. Check to see that the joint closes up on both faces. Make sure the pressure is consistent across the width and length of the joint. Bang the boards flat onto the clamps at their ends where they tend to lift up.
 

Use enough glue that you get some squeeze-out when you apply clamping pressure. Use a C-clamp to keep the ends lined up flat or a dead-blow hammer to coax the boards into place.
 

	Check both faces for squeeze-out and add a clamp, if needed. Also check to see that the boards are sitting flat on the clamps.

Check both faces for consistent clamping pressure. Add more clamps if needed to get a good consistent pressure. Alternate the clamp heads to even out the pressure.

Reinforcing edge joints
An edge joint mates long grain to long grain, which allows ideal gluing surface. For that reason, a glued edge joint has great strength, even without the addition of reinforcements. Tests have shown that an edge joint properly jointed and glued with modern adhesives has greater strength than the original solid wood.

So why reinforce an edge joint? Reinforcements in the form of biscuits, dowels, splines, or tongues and grooves make alignment much easier. Beyond this, reinforcements provide a mechanical connection, which strengthen the joint. Without them, you must depend on the adhesive alone to hold the joint together.

Splines help align edge joints and can be used decoratively. Use plywood splines or use solid-wood splines with their grain running across the groove for the best strength. It's easier to cut a spline to match the grain direction of the mating boards, but it's also easier to break it along the long grain.

A tongue-and-groove joint is another effective way to join edges. The key to making a strong joint is designing and cutting it to the right proportions.
 

	Cover the edges of sheet-good material with a simple edge lamination.

Edgebanding
Sheet goods are invaluable in cabinet construction, but plywood edges are ugly. Although commercially available edgebanding may be a quick solution, custom edgebanding is more durable and certainly more elegant (see Edgebanding options). Making your own edgebanding allows you to match stock color, especially for unusual species. Custom edgebanding also means more design options, including profiles.

Gary Rogowski has been building furniture since 1974 in Portland, Oregon. He has taught furniture making classes and workshops around the country for 21 years. In 1997 he opened The Northwest Woodworking Studio, a woodworking school in Portland. He is contributing editor to Fine Woodworking magazine, the author of Router Joinery