Three Ways to Make Edge Joints
By hand or power? With a spring joint or not?
by Robert W. Lang, Glen D. Huey & Christopher Schwarz
From the April 2009 issue #175
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One of the most important joints in woodworking is the edge joint. Without it, our projects would look like they had been built from narrow popsicle sticks.
The joint bewilders many amateur woodworkers – perhaps because there are so many ways to go about it. Which method is best? Which tools are best?
The senior staff of Popular Woodworking rarely agrees on anything (except the pizza place at which we sometimes eat lunch). And making edge joints is no exception. We do, however, agree on one principle when it comes to edge joints: You aren’t going to get consistent results by making your edge joints with a table saw blade.
During the last decade or so we have tested a dozen table saw blades that claim to give you rips that are clean enough for an edge joint. Perhaps that is true if your work is on a job site, if you are working in easy-to-compress softwoods, or if you are a fanatic about keeping your saw exquisitely tuned. But we have not found these saw blades to give us results that are 100 percent satisfactory.
And so we look to other tools and machines to create edge joints that result in seamless seams and maximum glue adhesion.
This joint has always made woodworkers edgy (sorry). Early written accounts of making edge joints would tout a variety of approaches as the best to ensure the finished panel stayed together.
Some accounts recommended loose splines. Some recommended using a tongue-and-groove joint. There was even a special kind of nail that could be used for joining edges. More modern methods of reinforcement include dowels, biscuits, Festool Dominos and pocket screws.
However, we contend that if you have two surfaces that will mate perfectly then you don’t need additional reinforcement. A well-made glue joint is stronger than the wood surrounding it.
Another area of confusion: Other early accounts recommend using a “spring joint” when gluing up a panel. A spring joint is when the edge joint has a small gap (only a few thousandths of an inch) in the middle of the seam. When you clamp across the middle of the panel, it closes the entire seam.
The advantage of a spring joint is that you use fewer clamps to make your panels. Also, if your stock is a little wet, a spring joint can keep the ends tightly together as the stock dries out (end grain loses moisture much more rapidly than face grain).
Some opponents of spring joints say that the gap introduces some stress into the panel that could (in time) cause the joint to open. Other opponents say that spring joints are simply a waste of good shop time.
In our shop, the opinion is divided.
Publisher Steve Shanesy and Senior Editor Robert W. Lang don’t use spring joints. And so we’re going to show Lang’s approach, which uses a powered jointer without any special setups to introduce a spring joint.
Senior Editor Glen D. Huey likes spring joints as a way to reduce the number of clamps he needs to use. He figured out a fairly simple jointer setup and hand trick that makes spring joints an easy thing to do on the powered jointer.
And then there’s me. I like spring joints and I like making them using handplanes. And so I’m going to show you how to make an edge joint using historical methods I’ve dug up from the old books.
So step away from your table saw for a moment and take a look at these three time-tested techniques and decide which one would be best for you. — Christopher Schwarz
Jointer – No Spring Joint
My approach to edge joining comes from my training in production shops, and my philosophy that a joint under tension increases the chances of failure in the future. I don’t use a spring joint, and I run edges over a well-tuned jointer just before gluing. There isn’t anything romantic or inspiring about my approach, but it works well, and it doesn’t take long.
I’m a bit persnickety about machine set-ups, and I get cranky if I have to remember what area of a machine is off a little, and in what direction that offset is. In truth, I have trouble remembering things like that, so it’s easier to have the jointer knives even with the outfeed table and the fence square.
I select wood for panels and tabletops based on appearance. You can’t convince me that there is an advantage to alternating growth rings, or arranging the boards so they will be easy to plane later on. The goal is to make a pieced-together board look like it grew that way. If the material is prepared correctly I don’t worry about it warping, and if I need to fuss a little when doing the final smoothing, that’s OK.
This is an area where mastery of the fundamentals is the key to success. Dead-flat boards with straight and square edges are easy to put together. Glue them together on a flat surface and it can actually be an enjoyable, relaxing experience. If the boards are straight and the thickness consistent before gluing, there is little to be done afterwards.
I crosscut the rough lumber to about the size I need, but when I surface, edge and rip I’m thinking WAP and TAP – “wide as possible” and “thick as possible.” This leaves some margin for me to work around defects or ugly spots without starting over. I try to keep parts from a single board together to make it easier to match color and figure.
There may have been a time when a spring joint made sense, especially if the moisture content of the wood was too high. In this day and age, it makes as much sense as collar stays and celluloid dickies. — RL
Jointer – With Spring Joint
I prepare my edges with a jointer, but I also like a small spring in my joint. Because I’m not a handplane aficionado, I turn to a machine. As a result, I have to bend the rules.
In most articles on setting jointer knives you’re instructed to use a dial indicator to set the knives perfectly level and in line to the outfeed table. That’s bunk.
While you do need to set the knives level to one another, alignment with the outfeed table is optional. I set my knives so there is .030″ of slope over the 8″ blade. The end of the knives closest to the operator are below the outfeed table by .015″. At the back they are .015″ above the outfeed table.
With the knives below the outfeed table, you’ll get a taper if you transfer hand pressure to the outfeed table as soon as there is ample surface to do so. That’s another rule I choose not to follow given my blade arrangement!
When edge jointing, I keep my downward-pressure hand at the center of the board. As the board runs over the knives it climbs slightly above the outfeed table. At the center of the board my pressure transfers to the outfeed table and the slight tapering effect completes the cut. Bingo, a spring joint.
And don’t worry about flatness when face jointing. Because a jointed face is not the final surface when milling for thickness, any small variations are erased at a planer. And if you’re worried about the small bevel on the edge of a 3⁄4″ board, you’re looking at less than a .003″ variation.
Bottom line: I can dial in my spring joint by adjusting my fence position along the blades. When everything works as planned, I need only one clamp for most panel assemblies, but I generally use two. (To see how this process works for faces and edges, go to popularwood
working.com/video.) — GH
Though I first learned to prepare edge joints by machine on a powered jointer, I prefer to do it by hand whenever possible. When I’m working for myself and time isn’t a concern, I’ll use the pure hand-tool methods shown here. It’s a bit slower than the power-tool methods, but I enjoy it immensely.
When every second counts, however, I’ll prepare my edges on a power jointer and then use a jointer plane to introduce the spring joint. You can mix and match the hand and power methods any way you see fit.
Here are a couple details and subtleties of my process. Though I use a scrub plane to dress my rough edges, you can also use a table saw, band saw, drawknife or a hatchet for the coarse removal of material.
Also, the cutter in my jointer plane has a very subtle curve on its edge. This allows me to correct an out-of-square edge by shifting the plane left or right on the edge of the board. But the curve is not so pronounced that it produces a curved edge on the board. The edge looks flat to a try square.
You can read more about this process in the August 2005 issue (#149) of Popular Woodworking in an excellent article by David Charlesworth titled “Learning Curves.” And you can find it online at popularwoodworking.com/apr09. — CS