For the woodworker building furniture and cabinets, the sliding dovetail is a joint well worth mastering. Strong and versatile, it has many applications, from case construction to leg-and-rail joinery.

You’ve at least seen a drawing of the joint. It’s a hybrid of the dado and the dovetail, with a groove in one part, a tongue on the other. Because both the groove walls and the tongue sides are angled like a dovetail, the joint has to be assembled by sliding the tongue into the groove from one end.

The inward-slanting walls of the dovetail groove prevent the tail from pulling straight out. To assemble the joint, you slide the tail into the groove from the end.

The mechanical lock of the sliding dovetail joint makes it easy to assemble, because the parts won't fall apart while you look for clamps. You only need two hands. What a concept!

Those canted walls give the joint a decided strength advantage over a dado. The joint mechanically resists tension, meaning that the tailboard can’t pull away from the grooved board. Even without glue, the parts stay linked together. The wood must crush or break before the two parts separate.

This characteristic of the joint simplifies assembly routines. You won't have parts collapse while you’re fumbling with clamps. Two hands usually are sufficient for assembling even multi-part casework, like a chest of drawers. Slightly bowed panels sometimes can be pulled into line without elaborate clamping configurations.

The joint has another singular advantage: If left unglued, it will allow the parts to move without coming apart. A breadboard end is the obvious example. You apply a narrow strip of wood across the end of a glued-up panel to conceal its end grain and to keep it flat. The joint — unglued — allows the tabletop to expand and shrink across its width, even though the end strip isn’t elongating and shrinking.

Other applications of the sliding dovetail abound:

• Join shelves to bookcase sides.
• Build drawers, joining the sides to the front and the back to the sides.
• Join aprons to table legs, and even rails to stiles, in frame-and-panel constructions.
• Mount moldings and case tops with dovetail keys or butterfly keys, holding them tight to the structure but allowing the wood to move.
• Mount battens to tabletops, lids, and doors to prevent them from bowing, doing this in the same way you’d mount a breadboard end.
• Make drawer runners and guides.
• Construct extension-table slides.

A chest lid's breadboard end, joined to the main panel with a sliding dovetail and glued only at the front, directs the panel's seasonal movement to the rear and keeps the panel flat to boot.

Even without a back, bookshelves constructed with tight sliding dovetails are free of wobbling or leaning out of square.

Joined to the underside of a tabletop with an unglued sliding dovetail, a batten keeps the top flat while allowing it to expand and contract seasonally.

Your very first tail-forming cut (left) should be an extremely shallow scoring cut, made to establish a crisp, chip-free shoulder. Additional passes on a set-up piece define the shape and whittle the tail's width (center) as you creep up to the optimal fit (right).

Cutting a Sliding Dovetail Joint

Laborious to cut by hand, the sliding dovetail is a relative snap to produce with a router (or two).

Each sliding dovetail joint requires two operations: 1.) cutting the groove and 2.) cutting the tail. Both operations are done with the router, and to get a good fit, you should use the same bit for both.

Grooves can be done with the router handheld or table-mounted. The location of the cut and the size of the cut itself usually will dictate which approach is optimum.

The tails, likewise, can be cut either way. The portable router generally requires jigging to steady it on the narrow edge being worked. As a consequence, most woodworkers cut the tails on the router table. There, you need nothing beyond all-purpose accessories like a push block and a featherboard or two.

Fits you do and don't want. (Do you need to be told which is which?)

Fitting the two pieces is a trial-and-error process. Ideally, you want the fit tight, but not so tight that friction stalls the tail as it slides into the slot. On the other hand, you don’t want the fit to be too sloppy— however easy that makes the joint to assemble.

The usual fitting technique is to plow the groove, then creep up on a tail dimension that fits that slot. If the actual groove is more than 3" long, you ought to make a short “fitting” sample of it. You can slide this across the full-length tail to determine whether you have wide spots that will make assembly of the joint difficult. Similarly, you should make a short “fitting” sample of the tail, which you slide through the groove.

To get the groove as right as possible, try making two passes through it, making a special effort to keep the work against the fence on both passes. If you do get a bump on the first pass, you may trim off the high spot on the second. The same is true of the tail.

Choosing a Bit

Dovetail bits are made in a variety of diameters and angles. Most half-blind dovetail jigs require a 1/2" diameter 14-degree bit on a 1/4" shank, so I’d say that’s the most common bit. But thanks to the prevalence of through-dovetail jigs, you can buy bits with 7-degree tapers, as well as with 7-1/2-degree, 8-degree, and 9-degree tapers. These angles yield more of a hand-cut look.

A benefit of these bits — one that’s pertinent here — is that they allow deeper cuts. Check out the comparison drawing. A 1/2"-diameter, 14-degree bit can cut only 1/2" deep because, at that point, the bit has tapered to a 1/4" diameter. At the same spot on an 8-degree bit, the girth is about 11/32". When the cut has narrowed to 1/4", it is 13/16" deep.



While you can buy bits that are larger and smaller than 1/2" diameter, that size is optimum for stock between 5/8" and 7/8" thick.

Scaling the Joint

A sliding dovetail is an effective, low-effort joint for mounting a breadboard end. Be wary of using it where heavy elbows will test it regularly, however.
Assembling a long joint ― such as a breadboard end (top) or a batten (bottom) often requires considerable force. Since you aren’t gluing the parts, and there’s going to be some seasonal movement anyway, go ahead and apply paraffin wax to the slot and the tail. Even so, as friction builds, you’ll have to whack the batten with a dead-blow mallet to keep it moving.
A shouldered sliding dovetail combines a shallow through dado with a stopped dovetail slot. For a chest of drawers, the drawer divider is housed in the dado and captured by the dovetail slot. The drawer runner is housed ― unglued ― in the dado and joined to the divider with an unglued mortise and tenon. A fastener at the back secures the runner.
Roughing out a groove with a straight bit clearly reduces the work the dovetail bit must do.
Yes, the heads do twist off dovetail bits. Usually it happens when you try to hog a long, deep groove without first wasting the channel with a straight bit. But this one expired ― after 20+ years of service ― while completing a previously wasted 3/8"-deep groove and wouldn't you know, just 3/4" from the end of the job's last groove). No physical danger involved, but the bit is now scrap and the job remained uncompleted until I could get a new bit.
Switch bits (or routers) and recut the groove, transforming it into a dovetail groove. If you have two routers with the same base diameter, you fit one with a straight bit, the other with the dovetail bit. Keep the guide fence in place and just switch from one router to the other.
Withdrawing the still-running router from a stopped cut made along a single guide fence can result ―inadvertently, to be sure ― in a botched cut. The tailboard's shoulders won't completely conceal the damage (yes, I checked). A fresh start with a new panel is the only flawless fix.
A twin-fence guide eliminates most of the risk in the cutting of dovetail slots, especially stopped ones. If you have two routers with the same base diameter, you can use one for the "wasting" cut with a straight bit, the other with the dovetail bit.
The dovetail bit tends to curl the right-hand edge of its cut as it enters the wood and invariably blows out the left-hand edge (left) as it emerges. Clamp scrap to both edges of the work for clean cuts. (Light sanding removes the surface fuzzies, which in any event will be covered by the tail's shoulders.)
Get set up for stopped dovetail grooves. Lay out the cut center lines. Chuck a straight bit in one router, a dovetail bit in another. Screw a stop to the twin-fence jig. Pinch a scrap strip between the jig's crossbar and the workpiece edge. Align the jig, clamp it and the workpiece to the benchtop. And get routing!

For casework, a shallow sliding dovetail — say, 1/8" deep — is all you need. Even in a dado joint, that depth is sufficient to withstand the shear stresses applied to a cabinet and its parts. Add the dovetail angle and you reap the mechanical blessings it confers. Yet that cut depth is easy for any router in a single pass.

The groove in a breadboard end, on the other hand, should be as deep as you can make it without compromising the groove-wall thickness or the thickness at the base of the tail.

Where the joint would experience the greatest stresses is in a tabletop. If it seemed likely that someone would lean their elbows heavily on the breadboard end itself, leveraging the joint, I’d choose a different joint (multiple mortises and tenons, for example).

Length must be considered when scaling a sliding dovetail. The longer a joint is, the more problematic it is to fit. I don't know if it's anomalies in the wood or just bad karma. Achieving a consistent fit along all 24 inches, more or less, of a breadboard-end joint is virtually impossible.

In casework, you would do well to avoid a sliding dovetail that's the full width of a side. It's one thing to make an 8" or 9" sliding dovetail that joins a shelf to a side in a pine bookcase, and quite another to assemble a 16" to 18" sliding dovetail in hard maple. Confronted with this length of joint, I'd suggest a shouldered sliding dovetail, which integrates a shallow through dado with a deeper stopped dovetail at the case front.

Grooving a Face

For casework or bookshelves, where the dovetail groove is cut into the face of the boards, I use a portable router, guiding it along a clamped-on straightedge. A shop-made T-square is perfect.

If you are cutting a 1/8"-deep slot and using an 8-degree bit, then cut away. But if your cut is deeper, say 3/8", and your bit is a 14-degree taper with a very narrow waist, it’s a good idea to “stage” the cut.

As I am sure you realize, a dovetail groove has to be cut in one pass at full depth. No such thing as doing it in multiple passes at increasing depths. The way to “stage” such a cut to reduce the stress on the router and especially the bit is to rout a groove with a straight bit that matches the dovetail’s waist diameter, cutting about 1/16" shy of the final depth.

In the example situation, you’d use a 1/4" straight, cutting — perhaps in two passes — about 11/32" deep. This is most convenient to do if you have two routers of the same base diameter, so you can set one up with the straight bit, the other with the dovetail bit. The fence position for both cuts ends up being the same.

Stopped Slots

The stopped slot presents a feed direction problem. Because of the dovetail profile, the cutter is trapped in the cut. Unlike a dado, you can't necessarily begin or end a dovetail groove just anywhere.

Consider this common situation. You are making a chest of drawers, and your plan calls for stopped sliding dovetails to join the drawer dividers to the chest sides. Typically, you lay out the two sides simultaneously, so cuts on the right side perfectly align with cuts on the left side.

Here's the feed direction problem. On one side the correct feed is from the edge in to the slot's terminus. But on the other, the correct feed is from the terminus out to the edge. Again, because of the dovetail profile, you'll probably want to make all of these cuts by feeding in from the edge, then carefully backing the cutter out of the slot.

On every stopped cut you make, you'll be feeding the router in the wrong direction part of the time.

Remember that when you feed in the correct direction, the spinning bit's rotational forces help keep the tool against the guide. When you feed in the wrong direction — when you make a climb cut, in other words — those rotational forces want to pull the tool away from the guide. When you rout a stopped dovetail slot, there’s a risk of the bit grabbing somewhere along the cut and pulling the router off the fence. That would ruin the cut.

I do know woodworkers who just rout along a fence, maintaining enough force to keep the router against the fence. You can try that approach, of course, and may have success with it.

A simple alternative is to plow the cut to the stopping point, then switch off the router. Let it wind down, then back the bit out of the cut. But this works only for one side of that chest-of-drawers project. The initial cuts on the second side are the climb cuts. Can't make those with the router switched off.

That said, I prefer to make stopped cuts with the router trapped between a pair of fences. If the router’s trapped, it can’t wander, regardless of the feed direction. I can plow into the cut and then back out, with the router running all the while.

The twin-fence jig shown is excellent for this work. If you have such a jig, use it. Failing that, bear in mind that cobbling together a twin-fence guide takes 15 minutes, 20 at most. All you need is four strips of plywood or MDF and a few drywall screws. Attach a stop to one or both fences to limit the length of the cut.

To aid you in sizing the tails that will fit into the slots you cut, use your setup to cut a slot in a scrap of the working stock. You avoid having to fit the test-cut tails to a slot in a case side itself, if you have this piece available.

Grooving an Edge


Doing an edge groove with a portable router is precarious. If you must do the cut this way, try using a laminate trimmer, since it is smaller and easier to perch on an edge. Or equip your router with two edge guides — if that's possible -- to trap the workpiece. Failing that, try one edge guide with a wide facing attached to the tips of guide.

A groove that's centered on the edge is the goal. Locate the center of the workpiece angle a rule across the end with full-inch marks on the edges and mark a dot at the 1/2" graduation. Use a square to stretch the dot into a centerline.
At the router table, park the workpiece at a straight bit, and adjust the fence so the cut will be just slightly outboard of the mark. Make a shallow end-to-end cut, spin the workpiece around and repeat the cut; the groove will be slightly wider than the bit but centered across the workpiece edge. Repeat the cuts until the groove is about 1/32" shy of the desired dovetail-groove depth .
Switch, then, to the dovetail bit and adjust the height for the full depth. Make an end-to-end cut, spin the work, and repeat. All done!
A climb cut made on the router table can be dangerous. To avoid an inadvertent climb cut, be absolutely sure you set up to position the initial pass to be outboard of the work's centerline. Note the step in the wasting cut being made at left. The first pass with the dovetail bit (center) produces a slight off-center groove, while the followup pass (right) centers the completed groove.
Use your "fitting sample" to set up the bit for cutting tails on the router table. Raise the bit until it skims the bottom of the groove.
You can cut tails for any sliding dovetail joint on the router table, even tails on large panels. Oh, it looks precarious, but really it isn’t. A well-placed featherboard is the secret.
Well-placed featherboards stabilize even a large panel standing on end. Here, a featherboard tandem is aligned on either side of the bit, and elevated with a block underneath so it's pressing above the cut. The fence is the one I use regularly; something taller isn't necessary.

In contrast, the setup and cuts are simple on the router table. There are two operations. First, you plow a groove with a straight bit. Then you finish the groove with a dovetail bit. The work is guided along the fence for both cuts.

The setup is probably obvious. The fence is positioned to center the cut on the edge. It's the same for both the roughing-out cut and the final dovetail cut. The workpiece is set on edge, tight against the fence and fed across the cutter, right to left.

It's good procedure to reduce the size of the bit opening in the tabletop as much as possible. If your setup doesn't have snap-in rings for this purpose, use a strip or panel of thin hardboard as an auxiliary top. Bore a zero-clearance hole by raising the spinning bit through it.

(If you have to move the fence to change bits—some router tables are like that—then set a reference block against the front edge of the fence at either end before you move it, so you can return it to the same spot.)

I can't think of a situation in which you wouldn't want the groove centered on the edge. To center it, you simply make a pass in each direction. That is, cut the groove, then turn the piece around and make a second pass.

Be sure that, on the second pass, you are cutting on the side of the groove closest to you, not the side closest to the fence. This is a safety issue. The latter situation represents a climb cut (assuming you feed the work in the standard right to left direction). The work could be snatched from your hand and fired in the direction you are feeding it. If the work disappears unexpectedly, your fingers could go into the bit.

Naturally, you should do your setup and make at least one test cut to ensure that you're content with the result before cutting the real workpieces. Save the test cut for fitting the tail (or make a separate piece for the purpose).

Cutting a Tail

This is always done across an end or along an edge. It is most commonly done on the router table. There are some alternatives, of course, but it is fast and easy on the router table, so let's focus on that approach.

Use the same bit for the tails as you used for the slots, of course. This guarantees the geometry will match.

Close down the bit openings in the tabletop and fence as much as possible. For the tabletop opening, use the appropriate reducer in your router mounting plate, or a 1/8" hardboard auxiliary tabletop. For the fence, either close split facings in against the bit, or apply a one-piece auxiliary facing and cut a zero-clearance opening with the bit.

Set the height of the bit above the table to match the depth of the groove or slot. If you cut the slots on the router table, move directly from that to the tail cut without changing the bit setting. If you cut the slots with a portable router, use your cut sample as an aid in setting the bit height. You'll "prove" the setting with test cuts, of course.

Bring the fence into position, housing all but the very edge of the bit in the fence. Depending upon the size and proportions of the workpiece, you may want to add a tall facing to the fence. This may be worthwhile to you if you're working on something like a tabletop or chest lid, although I've found a well-placed featherboard (and my regular fence) is all I need for even these big pieces.

The most common approach to actually cutting the tail? Make it fat initially and, in a series of adjustments, work to thin it down just enough to fit the slot. Remember as you adjust the fence after the first cutting that you’ll be doubling whatever amount you move it, because you make two passes to form the tail. And since moving only one end of the fence halves the change at the bit, you should move one end of the fence the amount you want to change the cut. Confusing, huh? Here’s an example. If the tail is 1/16 inch too wide, move one end of the fence 1/16 inch. This changes the cut by 1/32 inch at the bit. Taking 1/32 inch off each side of the tail will reduce its width 1/16 inch.

How you hold and maneuver the work depends on its size. You can stand a relatively narrow workpiece on end, back it up with a square-edged piece of scrap (both for support and to prevent tear-out), and slide it along the fence through the cut. Keep your fingers above the cutter. If the piece is headed for a stopped groove, you can cut an edge along with the faces.

Using a Handheld Router: Routing a tail with a handheld router is as dicey as routing a dovetail groove with the tool. But the consequences of a bobble in mid-cut aren’t as disastrous. The cutter is grazing the outer surface of the board, not trapped inside it. If you tip the tool away from the work, you get a bump in the cut, which a second pass removes. Tip the other way, and you get a gouge. It’ll be hidden inside the groove. Not a calamity.

Whether the tail piece is narrow like a drawer divider (left) or wide like a shelf (right), stand it on end, back it up with a scrap block, and advance it along the fence. The backup block minimizes exit splintering and helps stabilize the work, reducing its tendency to "walk" along the fence. Make a cut, spin the work 180 degrees and cut again to form the tail.
For a stopped slot, trim one edge of the tail. Simply turn the piece to register its edge against the fence. Use that backup block, and cut. To snug the tail's end against the slot's end, you can pare the sharp corners with a chisel. (I seldom bother.)

But you do have that business of balancing a large, dynamic tool with a sharp, high-speed cutter sticking out of one end on a bitty, narrow edge. To control the cut, you need an edge guide — or two. The smaller the router, the better. The cut isn’t heavy and thus doesn’t require brute power. I’d use a laminate trimmer.

But I’d only use this approach with a reasonably wide workpiece: a chest lid. a bookshelf. Not a 3-inch-wide drawer divider for a chest of drawers.

Here's a quick-and-dirty setup for routing tails. Its advantage is that the very router and bit setup that cut the grooves will cut the tails. Square up a short piece of ordinary 2 x 4 and clamp it to the router's base. Switch on the router and swing your "fence" against the bit, burying it. Expose just a tip of the bit and apply a second clamp. To increase the cut (thus narrowing the tail), loosen one clamp and tap the block to expose more of the bit.

A laminate trimmer has enough power for a tail cut, and it’s the right size for balancing on the edge of a panel. Fit it with an edge guide with a wide facing, and you’ll be able to cut the tail with a handheld router.

Fitting Tail to Slot

Regardless of your tail-cutting approach, the routine is the same. Make a test cut on a scrap of the working stock. The scrap must be exactly the same thickness as the real work. I think it's most effective to creep up on the fit. That is, start with a "fat" tail and check it against the grooved sample. Make a fence position adjustment, recut (on both sides of the tail), and recheck the fit. I keep trimming the initial sample until I get the right fit. My final assessment, however, is based on a fresh sample.

Fitting the tail to the groove is a progressive trial-and-error process. The initial cuts establish the correctness of the vertical depth (left); the shoulders must be tight to the surface at the same time that the tail's end is tight to the groove bottom (right). (Adjust the bit and begin afresh if this fit is off.) Judge how much the tail's width must be reduced to fit the groove. Pare little by little until the tail penetrates the groove.

How tight you make the fit depends on the application. A short joint, such as one that joins a drawer divider to a case side, should close at least halfway with hand pressure and require only a tap or two to seat. You'll be able to assemble it with glue, and the glue line will look nice and tight.

If you have to pound the tail into the slot, it's too tight for gluing. If it slides home with firm hand pressure, the fit isn't ideal, but the joint will hold well when glued. Finally, if the tail piece sides into the slot easily, and especially if it wiggles from side to side, you need to start over. The tail is too small.

The most problematic joint to fit is a long one, like a breadboard end. You aren't going to glue it (except at one end), because it is cross grain. You do want it tight, so the seam at the shoulder isn't gappy. But as the tail slides through the groove, the friction builds, and even without glue it can be tough to drive home. Obviously, you only want to assemble this joint once.

A long joint is the most problematic to fit. You only want to assemble the joint once, but you don't want to do that only to have it seize an inch or two shy of the end. Best testing option is to use short gauges, one with the final-dimension groove, another with the final tail, to pass across ― or through ― the full tail or groove.

So how do you test the fit without assembling the joint? Use your final test cut samples as gauges.

Slide the groove sample onto the tail and work it from one end to the other. This should help you isolate really tight sections, where you may want to sand or pare the tail. Do this on each long tail. Likewise, slide the tail sample through each long groove.

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