Feature 7
The most popular joint in woodworking is the dovetail. In this feature, you will learn about important design considerations to help you make dovetail joinery that will be both strong and beautiful.
In this article, Ian Kirby delves deeply into the lore of the dovetail joint, demonstrating the different types of dovetail joints and the steps you must take to create stunning dovetails for your projects.
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| Too much slope and the corner is likely to break off because of fragile short grain. Too little slope and the joint looks like a finger joint gone wrong.
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| Half tail on outer edge. |
Half pin on outer edge.
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| Half pin on outer edge, with mitered corner.
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Half tail on outer edge, with mitered corner. |
| The lines of the outer edges of the joint are affected by four corner options. Starting with a half pin is more attractive, but there is no technical reason to prefer this option over a half tail. A mitered corner unifies the sides and top.
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| The end grain is always more dominant than side grain because of the structural nature of wood and because it soaks up more finish, becoming darker. This layout creates a boring pattern because the visual weight of each end grain is too similar. The vertical grain of the pins between the end grain of the tails is less refined than that on the layout below because the pins are so large.
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In this layout, we see the tails more powerfully as an entity in plan, and the pins take on a finesse because they are smaller. The band of end grain on the elevation is pierced by fine lines which emphasize the delicacy of the pins. In both instances the pattern is repetitious end to end. We don’t have to follow this formula.
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| In this layout, the two small outer tails add variety and visual weight at each end. They also create five glue lines very close to the outer edges. This prevents the edges from curling up and, if used on a large structure, resists the stress of lifting usually applied in that area. The tail between the twin pins is the same size as the outer tails, lending a strong sense of continuity when seen in elevation. |
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| Probably the most dramatic version of the through joint is the hound’s tooth dovetail. This layout has small tails and pins sitting between larger ones. |
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| Knife the shoulder and rabbet lines with a cutting gauge — two settings produce a total of six lines.
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| Chamfer the end of the rabbet with a chisel (left) to prevent breakout when planing. Then cut your rabbets with a shoulder plane, as demonstrated at right.
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| Mark out the pins. |
Mark the corner miter. |
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| Chamfer the miter end with a chisel, as shown above to prevent breakout when planing.
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Then you can remove most of the miter waste with a shoulder plane.
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| Saw the pins. Be sure to first establish the line across the end grain, then saw down the vertical line. |
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| In the drawing above, you can see all gauge lines marked, plus miter. You make six cutting gauge lines with two gauge settings. Pin and tail pieces are flipped from normal assembly position to make gauge lines visible. |
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| Left, chop across the grain up to 1/16" of shoulder line to remove what comes easily. Then (right), chop slivers down the grain to 1/16" of the rabbet line — no fallout. |
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| Return the work to the bench and chop carefully into the corner of the socket to clean out the bulk waste.
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| Clamp the parts to position the pins and mark out the tails.
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Mark the pin sockets for clarity.
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| Then saw the tails, blowing sawdust from the kerf as you go.
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| Clamp the pin piece in the vise and sever the corner end grain fibers with a skew chisel.
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| Continue the socket cleanup with a chisel narrower than the height of the pin so you can see the sawn pin face that guides your cut. Clean up the end wall by vertical paring, using the rabbet as a guide.
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| Check the back wall cut for parallel: press a chisel against the wall and check against a straightedge.
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| Check bottom of socket (left) for square. Tail sockets (right), cleaned out by careful chisel work, are ready to mark out the tails.
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| Saw the miter but leave the knife line.
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Cut the open socket miter about 1/8" deep by vertical paring.
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| Clamp the workpiece in the vise at 45° and pare to finish, using the land from the vertical cut.
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| Assemble the joint. Over-tight areas will show themselves by crushed tissue. Adjustments can be made to these areas after the joint is parted (using a protection piece, right). |
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| Cut the miter to size using a shoulder plane (left),then close the joint and enjoy.
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Few aspects of woodworking evoke as much emotion as the dovetail joint. The through or common dovetail in particular is seen to indicate some higher form of workmanship, some superior form of furniture detail. My friend Frank Klausz, who delights in showing how to make dovetail joints in a few minutes, tells us that in his early life in Eastern Europe it was the way to make packing cases. You can’t get more common than that! It also underscores that it truly isn’t a difficult joint to make and it doesn’t take long to make it. Having described in
Feature 5 &
Feature 6 through and single-lap dovetail joinery, I would like to focus now on the design of the joint because that’s what really matters. An ugly dovetail joint, no matter how well-made, is still ugly. I also will show how to make a secret miter dovetail.
Elements of Design
Designing the joint has two aspects: one minor and one major. The minor one is the slope you choose for the interface between pins and tails. This slope matters to the tail: too much slope and the corner is likely to break off because of fragile short grain. Too little slope and the joint looks like a finger joint gone wrong. Because there is nothing in the woodworker’s tool kit graduated in degrees, we use ratios to make slopes. A slope of somewhere between 1:4 and 1:5 makes for an elegant solution.
The major aspect of the design is the layout, the relative size of pins and tails. Over time, woodworkers have come to accept the following layout principles: tails are made bigger than pins. The tails go on the longer side of a rectangular case -- on the front if it’s a chest, on the top if it’s a sideboard.
Some of the most elegant single-lap dovetails ever made graced drawers during the late 1700s and just after the time of Chippendale. The pins were so fine that, when cutting the tails, the maker started the second cut of the pin socket by entering the saw into the first cut. In some of these drawers, the ratio of tail wood to pin wood was about 19 to 1. That they rarely broke is worth considering when discussing the strength of this joint.
Design Details
Although we laud the dovetail joint, the reality is that it’s a design detail in terms of furniture. It is only seen at close quarters and it has nothing to do with the general form or the proportions of the piece and its parts, which are the primary design elements. Nevertheless, it’s a detail that can be designed well or poorly. I’m not referring here to its execution — tightness of shoulders and faces — getting execution right is a matter of practice. I’m talking about the pattern value that we create on the row of end grains and shapes when we design the joint.
Strength of Dovetails
The joint has to be very poorly made or poorly designed not to resist considerable stress: in other words, it’s inherently strong because of interlocking parts that are also glue faces. The combination of layout design and accuracy of fit affect strength, and given that you control both of these things, strength is not an issue. Furthermore, dovetailed cases are subjected to far less stress than mortise-and-tenon joints on tables and chairs.
Designing With Confidence
If you are setting off to make a piece of work using dovetails, say, a blanket chest or a handmade drawer, then spend some time drawing different layouts before committing to the work. Draw them full-size and as accurately as possible, as if you were making a working drawing, which in the end is what you’ve got. Whatever you do, don’t set off to make four rows of dovetails and think that it’s OK to lay them out directly on the wood: you sell yourself short that way.
Start with the joint at the outer edges, which requires some design decisions. You can begin and end with a half pin or a half tail. You can miter the corners or leave them with square shoulders. All of these possibilities are illustrated at the bottom of the lesson.
A Hidden Argument
Making a dovetail which is hidden probably seems odd to a woodworker who is struggling to make the through joint. For the sake of completeness, I’m bound to include the two hidden joints as part of the handmade and solid wood basic inventory of methods and making handed down to us. There are circumstances when a through joint detracts from the design of a piece or the exotic wood used to make it. The benefit of dry position holding as the piece is being made is an advantage, and the permanence of the glued joint is undeniable.
Making a Secret Miter Dovetail
If you have made a single-lap dovetail — the one typically used on a drawer front — then you have learned the necessary sawing and chiselling skills to make a secret miter dovetail. As I’ve explained earlier, this joint is normally used when you are working with highly figured or colorful wood so as not to compete with its beauty. However, for the sake of clear photographs, I used Honduras mahogany. For your first attempt, so should you. These are the dimensions of the pieces I used: 4-3⁄4" x 11/16" x 18".
Marking Out
Begin the joint by making a rabbet at the end of each piece. The marking out is done with two gauge settings.
First, set the cutting gauge to the thickness of the wood. Knife the shoulder lines on the inside faces — the face sides. Knife around the corner on the edge, about one-quarter of the way across. Next, set the gauge to 3/16" and knife the lines that will define the rabbet.
Cutting the Rabbets
I use a shoulder plane. You could use a router or a table saw for this operation, but you still have to use a shoulder plane to complete the miter once the joints are cut.
Laying Out the Joint
The secret miter joint cannot be made tails first like the three other dovetail joints. Why it must be made pins first will become obvious further into the exercise.
Marking the Pins
There is no need to vary the pin and tail size as we do on a through joint. The joint is easier to make if tails and pins are about the same size. What you do have to do is decide how many glue lines you want for the job in hand to be strong enough.
I mark the corner miter after laying out the joint. It could be done earlier, when the gauge lines are cut. It’s your call. Before sawing the joint, cut most — but not all — of the end miter with chisel and shoulder plane. The unfinished miter serves two purposes: as a reference stopping you from over-sawing the joints; as a land for the chisel when paring the end walls of the sockets.
Sawing the Pins
The saw cut is similar to any of the closed socket cuts you make in dovetailing. Saw across the end grain and establish that line, then saw down the vertical line. Divide and conquer. The trick to making a clean kerf is to keep the saw in the end grain kerf as you saw down the vertical line.
Chiseling Out the Waste
Cleaning out the closed sockets is the same for tails and pins. Lay the workpiece on the bench and chop across the grain in small bites to within 1/16" of the shoulder line. Put the workpiece upright in the vise and chop with small bites to 1/16" of the wall.
Return the work to the bench and clean out the bulk waste by chopping carefully into the corner of the socket. Then clean out the socket by using the sawn faces as a guide. First cut the end grain fibers using a skew chisel; otherwise, the waste on the socket end wall won’t come free. Note that to clean up the socket I use a chisel that’s narrower than the pin is high. This gives a much better read on the plane the chisel must follow.
Clean out the waste from the end wall by vertically paring with the work in the vise. The edge of the workpiece is aligned with a clear pencil line marked on the bench. That line is at parallel and perpendicular to the extension bar on the vise. When the workpiece is set against the bar and aligned with the pencil line, it’s held vertically.
Check your chisel work for square in both planes and, when you’re satisfied, that’s the first part done.
Marking the Tails from the Pins
The next task, marking the tails from the pins, requires a new technique. No matter how large or small the case that you’re making, the two parts must be held in place by clamping because it’s impossible to hold them by hand. I clamped the two parts to the bench. Another way is to clamp the tail piece to the bench with two C-clamps, leaving the joint projecting from the bench about three inches. Then clamp the pin piece to it — it’s your choice.
Whichever way you do it, if the other end is already jointed, use a clamping block big enough to avoid damaging the mitered end. Marking is best done with a sharp soft pencil. On most woods, a knife line just fades into the grain. A pencil leaves a clearly defined line on the side you have to cut to. To avoid error, identify which areas must be removed. Another aid is to lay the completed pin piece in front of you as you cut the tail piece.
Sawing and Chiseling the Tails
Remove the waste and check for accuracy as you did earlier for the pin piece.
Once the pins and tails are completed, the next job is to cut the corner miters. Saw just shy of the knife line and chisel to clean up. Put the parts in the vise to chisel. The tail is straight forward. Use a chisel that’s a bit less than the length of the miter so you can better see what you’re doing.
The pin piece obliges you to chisel into a void. I chisel about 1/16" down to establish the miter, then put the piece in the vise at 45° and use the small land as a guide to complete it.
You can now put the joint together to check and adjust the fit.
Separate the two parts and clean up the miter with a shoulder plane. Close the joint one more time and there you have it, your first secret miter joint!
Machine-made Dovetail Joints
The first dovetail machine I used was a thorough-going industrial gem made by Brookman, an English company in a small village called Rothly.
In recent years, routers and dovetail jigs have become commonplace. There is no argument that they work: the smooth, tight mating faces produce ideal gluing conditions. Of the two design aspects I’ve explained, one of them, the slope, is a function of the router bit. It’s pretty much the slope we use in hand cutting. Most jigs have no provision for varying the layout. Of the ones that do, the pin socket size is controlled by the size of the router bit, the smallest of which is a bit bigger than the socket that can be made by hand. So on technical grounds the jig is first-rate; on aesthetic grounds it falls flat.
The Dovetail Family
Through Dovetail
More than any other joint, the through dovetail leaves nothing unsaid. The interfaces between the long grains and end grains demonstrate the hand skill of the maker, and the layout demonstrates the design skill. It’s usually the first dovetail joint you learn to make, but it should be viewed as just one of the family — no more or less a star than the other three.
Double-lap Dovetail
Only a thin strip of end grain announces that the double-lap dovetail is hidden inside. It’s a bit easier and quicker to make than the secret miter dovetail. It was mostly used on larger cases, such as sideboards or chests, rather than smaller cases, such as jewelry boxes and knee desks. When the end grain is molded with a scratch stock along with the long grain edges, the resulting shadow lines subtly define the architecture of the piece.
Single-lap Dovetail
The single-lap is the best known of the dovetails since it’s used to join the front to the sides of a drawer. Whether the drawer is housed in a veneered or solid wood case, opening it reveals the pedigree of the piece. At its best, if it’s a handmade drawer, the feel and sound of its opening is the prelude to enjoying the refinement of the thin drawer sides, the choice of wood, and the elegance of the single-lap dovetail joints. It’s an experience no longer available from the furniture industry, being too expensive for all but the few of discerning taste and limitless budget, and at the fingertips of amateur woodworkers with the will to make it.
Secret Miter Dovetail
Some woods that handmakers are privy to are simply so beautiful or so striking that a row of through dovetails, no matter how elegant, detract from the piece rather than enhance it. Similarly, some cases can be made so refined in their proportions that their quiet sophistication would be destroyed by a through joint. Or the wood may be so dark that the pattern value of pins and tails is scarcely visible.
For a downloadable PDF of this lesson, click here.
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