Half Blind Dovetail Jigs

The least expensive to buy and the easiest to set up are the many half-blind dovetail jigs. No matter how wide or thick the wood is, you clamp it into the jig, run the router through both pieces at once, and get equal-width pins and tails that are rounded to fit into each other at the back. This is the very institutional-looking joint that is often used to assemble drawers for kitchen or other production cabinets. The trickiest part of this one is to get the two parts offset just half a pin in the jig so they come out flush when you assemble them.

The worst part about this jig is the very fact that it is so foolproof and has been around long enough that macho woodworkers look down on it. Its perfectly even spacing is easy to recognize and everyone knows that even though your dovetails fit well and perform well, you didn't work your butt off to get them that way.

All of these jigs consist of a metal base with a clamping system to hold the mating workpieces and a comblike template to guide the router in cutting both pieces at once. The biggest difference from one brand to another, from one mode) to another, is the quality of the materials and hardware and the precision with which it's made and assembled. The cheapest ones have stamped parts that tend to flex and buckle, threads that strip quite easily, wing nuts that chew at your fingers. The expensive versions have basic parts that are extruded rather than stamped or die-cast. big plastic knobs instead of wing nuts, and a measure of adjust-

Adjustable Dovetail Template Jig

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DOVETAILS

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SOCKET

SOCKET PIECE

Router TechniquesWoodworking Jigs And Tips

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MALF-BLIUO

DOVETAILS

JOINTS PRODUCED BY TUE

Typical dovetail jig, template

.template bracket screw jiú to bench.

BASE

front clamp bar clamp kkiobs rab8ete0

MALF-BLIUO

DOVETAILS

JOINTS PRODUCED BY TUE

Typical dovetail jig, parts of a typical dovetail jig top clamp bar

CLAMP KNOBS

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TEMPLATE BRACKET KNOB

Stanley Dovetail Jig Model 92870

The typical dovetail jig makes half-blind dovetails, cutting both pins and tails at the same time with the same bit. Although this elderly Stanley model is no longer manufactured, it is nonetheless representative of the better grade of dovetail jigs. It has a rigid extruded aluminum base and durable phenolic template. Its large clamp-knobs are easier on the hands during extended dovetailing sessions than the wing nuts found on less-costly jigs of this type.

The typical dovetail jig makes half-blind dovetails, cutting both pins and tails at the same time with the same bit. Although this elderly Stanley model is no longer manufactured, it is nonetheless representative of the better grade of dovetail jigs. It has a rigid extruded aluminum base and durable phenolic template. Its large clamp-knobs are easier on the hands during extended dovetailing sessions than the wing nuts found on less-costly jigs of this type.

The typical dovetail jig with a one-piece template will enable you to rout flush and rabbeted half-blind dovetails. Some models also produce box joints.

ability'. Some even have additional templates that let you cut Winch half-blind dovetails in addition to the standard Winch variety, and Winch and Winch box joints as well.

You have to look em over and decide if you want to spend 40 bucks or three times that for a jig that basically produces a single joint. (You can make similar jigs yourself, but be prepared to spend a lot of time fine-tuning the templates to get the precision required to repeatedly produce the desired results.)

In addition to the jig, you need a router, a dovetail bit (usually the '/¿-inch, 14-degrce variety), and a guide bushing (usually one with a Mc-inch outside diameter, which limits you to a Winch-shank bit). The best router to use is a 1- or 1 Whorsepower fixed-base model. The ability to plunge is

For the sake of appearance (it won't affect the strength of the joint), you want to begin and end with a half-pin. But machinc-cut half-blind dovetails are inflexible. You can't alter their size to distribute them evenly across the width of board you're working with. What you have to do is alter the width of the board.

The ^-inch dovetail lays out on Winch centers. That is. the distance from the center of one pin to the center of the next is Vs inch. So, as the drawing shows, you should try to adjust the width of the work to achieve the even spacing.

irrelevant in this operation, and brute power doesn't contribute much, if anything.

Here's what is involved in setting up and using one of these jigs.

Setting Up

The first thing you want to do is get some wood for test cuts. It ought to be the same stock you are using for the drawers or boxes you are making. Just rough out an extra front and side. If you have to make more than

With your router and the typical dovetail jig,you can cut dovetails in different thicknesses of stock. It's not unusual, for example, to make drawers with Y+inch-thick fronts and V2-inch'thick sides and backs. This doesn't present any difficulty. Even in plywood, the router cuts excellent dovetails without a hitch. From top to bottom, these dovetails join a '/2-inch front and side, Y+indt front and '/2-inch plywood side, Y*-inch front and '/¡-inch solid-wood side, and Y*-inch front and side.

Router TechniquesRouter Dove Tail

With your router and the typical dovetail jig,you can cut dovetails in different thicknesses of stock. It's not unusual, for example, to make drawers with Y+inch-thick fronts and V2-inch'thick sides and backs. This doesn't present any difficulty. Even in plywood, the router cuts excellent dovetails without a hitch. From top to bottom, these dovetails join a '/2-inch front and side, Y+indt front and '/2-inch plywood side, Y*-inch front and '/¡-inch solid-wood side, and Y*-inch front and side.

one complete test cutting, simply crosscut the dovetails off each test piece and try again.

Set up the router. Install the Ji^inch guide bushing in the baseplate. Then adjust the router so the collet is relatively close to the bushing and carefully insert the Winch-shank bit. Tighten the collet nut.

Adjust the depth of cut next. The usual setting is Yi inch, though your jig's instructions may specify some other figure.

The last step in router setup is to check that the bit is centered in the bushing. Rotate the bit by hand— be sure the machine is unplugged, not merely switched off—to ensure that the bit doesn't contact the bushing anywhere and that it is centered. If it isn't centered, try to shift either the bushing or the entire baseplate to correct the problem.

Set up the jig itself. Most jigs need to be attached to a Winch plywood base, which can then be clamped to a workbench. Obviously, the jig has to be positioned at the edge of the bench, so the drawer or box side can be clamped in the jig.

The workpieces have to be clamped in the jig in a particular way. The socket piece, which has the pins—it's the drawer front—is clamped to the top of the jig. The

The first thing youl I notice when insertingyour '/2-inch dovetail bit through a Vurinch guide bushing and into the router collet is that the largest part of the bit doesn't fit through the hushing. So when you set the depth of cut, turn the bit slowly by hand to absolutely ensure that the bit doesn't contact the bushing. Most guide bushings are steel, which will damage the bit's carbide if the two come into contact.

Router Techniques

Before setting the template in place, be sure the workpieces are properly clamped in the jig. Both should be snug against the alignment stops and snug against each other. The top end of the tail piece, which is clamped to the jig's front, should be flush with the top surface of the socket piece, which is clamped to the jig's top. Typically, the template is screwed to a couple of l.-shaped brackets. A slot in each bracket fits over a stud projecting from the jig base. A stop nut on the stud serves both to adjust the fore-and-aft position of the template and as a stop against which the lock-down nut or knob jams.

Before setting the template in place, be sure the workpieces are properly clamped in the jig. Both should be snug against the alignment stops and snug against each other. The top end of the tail piece, which is clamped to the jig's front, should be flush with the top surface of the socket piece, which is clamped to the jig's top. Typically, the template is screwed to a couple of l.-shaped brackets. A slot in each bracket fits over a stud projecting from the jig base. A stop nut on the stud serves both to adjust the fore-and-aft position of the template and as a stop against which the lock-down nut or knob jams.

Blind Dovetail

tail piece—it's the drawer side—is clamped to the front of the jig. The socket piece must be butted against the face of the tail piece. The end of the tail piece must be flush with the top surface of the socket piece.

Here's the easiest way to do it. Roughly position the tail piece in the jig, with its top end well above the jig. Slip the socket piece in the jig, and butt it tightly against the tail piece. Clamp it firmly. Now loosen the clamps holding the tail piece and lower it until its end is flush with the other workpiecc. Clamp it firmly.

Both pieces need to be against the alignment pins or stops. These stops align the two workpieces so that they are offset exactly Mt> inch. This is the amount they must be oflsct so the edges of the assembled joint will be flush. Every jig has these stops—they're adjustable if your jig takes more than one template—and it has a pair on the right and on the left. Use the pair on the left for now.

Fit the template in place next. If you have a choice, adjust it so it will yield a flush dovetail. The template needs to be flat on the workpieces. and the holdfast must be cinched tightly.

Now you are ready for your first test cut. Set the router on the template, its bit free of the work. Switch on the router and make a quick, shallow scoring cut across the tail piece, feeding from right to left (yes. this is a climb cut). This will help prevent the bit from pulling chips out along the tail piece's shoulder as it exits each cut.

Rout the dovetails, slot by slot, beginning on the left and working to the right. You may want to zip back through them when you are done, just to be sure you didn't pull out of a slot too soon, leaving the work or.ly partially cut.

Don't just lift the router from the template. The bit will ruin both the cut and the template. Instead, cut the power and pull the router toward you. getting it well clear of

Actually machining the dovetails takes only a few seconds. To ensure yourself of a clean shoulder on the tail piece, make a very light climb cut along the edge. Then work along the template, feeding the router as far into each template slot as it will go. The router cuts both sockets and tails at the same time.

the jig before lifting it. Take a good look at the work and be sure you haven't missed a spot. (If you have, rout it now. before moving anything.) Only then should you remove the template, unclamp the work, and test assemble the joint.

Fine-Tuning the Setup

Chanccs are. your setup needs a little fine-tuning. You slip the two test pieces together, and something's not quite right. Perhaps the fit is too loose. Or too tight. Or the sockets aren't deep enough. Or the pans are a little offset. All of these ilk are cured with some fine-tuning.

Fit too tight? The bit's cutting too deep. Reduce the depth of cut slightly.

Fit too loose? The bit's not cutting deep enough. Increase the depth of cut slightly.

Are the sockets too shallow or too deep? The template is misaligned. To reduce the socket depth, move the template veiy slightly toward you. To increase the socket depth, move the template away from you. Your jig's instruction sheet should explain exactly how to accomplish these adjustments on your jig. Just remember that as you alter the depth of the sockets, you are also altering the thickness of the tails.

Are the two pans slightly misaligned when assembled? The top and bottom edges should be flush. If they aren't, you may not have had the workpieces snug against the alignment pins. Or the pins may be slighdy misadjustcd.

Any other problems you have will stem from misalignment of the workpieces in the jig. Make sure the top surface of the socket piece is flush with the top end of the tail piece, that they are at right angles to each other, that the template is square to the workpieces. and so forth.

When you've successfully fine-tuned the setup using the alignment pins on the left, cut a test joint using the right end of the jig. Do any additional tuning needed there.

Cutting the Good Stuff

Before starting on the good wood, make sure you're organized for complete success. It doesn't matter if you are dovetailing one drawer or fifty drawers, it's all too easy to get mixed up and cut the dovetails in the wrong places. So label your workpieces.

Bear in mind that you must clamp the work in the jig in an orientation that seems calculated to befuddle. You probably noticed this when you

When adjusting the socket depth, you theoretically want the surfaces to come flush when the joint is assembled. But as a practical matter, it's better to have the socket piece just proud of the tail piece. That way a pass with the belt sander will bring the joint flush, without requiringyou to sand the entire side.

assembled the test pieces. When the workpieces are clamped in the jig, it's the assembly's inside faces that are exposed. What's exposed in the construction is hidden in the assembly. What's hidden during fabrication is exposed in the finished product. Confused now?

Do this. Label the parts on what will be their inside faces. If you can read the labels when the parts are in the jig, you've got the orientation correct. If you arc doing drawers, the sides always go on front.

labeling tue parts and tue jig
Routing Techniques

and the fronts and backs always go on the top.

And you need to label more than part names. Consider that each drawer or box has four joints. When you are doing machine-cut dovetails, two of the four joints must be cut on the left side of the jig and two on the right side. You don't want to get them mixed up.

The most simple organizational labeling system I've come across is shown in Labeling. There are few labels, but where you put them is as important as what they are. The labels indicate which is the inner face, and thus which face is up in the jig. The letters arc always associated with a particular pan. Each letter is placed at the bottom edge of the piece, to indicate which edge goes against the jig's alignment stops. On the jig itself, you mark two two-letter combinations beside each pair of alignment stops, as indicated in the drawing. As you clarnp the parts into the jig, orient the letters toward the stops, and check the combination. If it isn't on your list of two, you are at the wTong end of the jig.

A more commonplace approach is to label each piece with its pan name, to mark the bottom edge, and to number the joints in sequence around the assembly. The trick is remembering which joints get cut on which end of the jig.

Dovetailing a Lipped Drawer

More often than not. the half-blind dovetail jig is used in dovetailing drawers. Being limited to the flush version of this joint is a pretty severe design restriction, though. Very often you want to make lipped drawers, in which the drawer front has a rabbet cut around the inner face.

A few of the standard dovetail jigs have a template adjustment that makes it possible to cut this joint, and their instruction manuals lay out the procedure fairly lucidly.

But you can dovetail lipped drawers with any half-blind dovetail jig. The trick is to cut the fronts separately from the sides. What the template adjustment does, in those jigs that allow you to cut the so-called rabbeted half-blind dovetail, is to shift the template position Yh inch away from the operator, so the sockets can be extended that Yn inch. (This assumes, of course, that the rabbet around the drawer front will be Yh inch wide.) What you do is set up the jig, clamp the boards in place, and cut the pins and tails. Then you shift the template and make a second pass, extending the sockets.

You can accomplish the same thing by positioning the drawer front farther forward than its usual position and then routing the sockets in one pass. And you can accommodate most any width of rabbet. Here's hoxv.

Rough out the drawer parts, and rabbet the fronts. At the same time, cut some scraps of the drawer-front stock to use to back up the sides when routing the tails in them. And cut one scrap of the drawer-side stock to use in positioning the fronts in the jig. This scrap needs a rabbet across one end. The depth of the rabbet must be the same as the width of the drawer-front rabbet. For example, if your drawer-front rabbet is the standard Winch width, then the depth of the rabbet is Ys inch. And if the drawer-front rabbet is wider than the drawer-side stock is thick, you need to substitute a thicker scrap so that you can cut a rabbet to the necessary depth and still have a tab

Router Techniques Woodworking

To rout dovetails into a rabbeted piece, like a lipped drawer front, you have to rout the tails and sockets in separate operations. This is because the socket piece has to be brought forward from its usual position. A rabbeted positioningjig is clamped in the tail piece position, as shown, and the end of the rabbeted socket piece is butted against the side of the jig's rabbet. Once the socket piece is secured,you can remove the jig, place the template, and rout the sockets.

To rout dovetails into a rabbeted piece, like a lipped drawer front, you have to rout the tails and sockets in separate operations. This is because the socket piece has to be brought forward from its usual position. A rabbeted positioningjig is clamped in the tail piece position, as shown, and the end of the rabbeted socket piece is butted against the side of the jig's rabbet. Once the socket piece is secured,you can remove the jig, place the template, and rout the sockets.

left against which to butt the drawer front (as you'll see in a minute).

Finally, if the rabbet extends across the top of the drawer front as well as along its sides, you need a spacer. The spacer offsets the drawer front from the alignment stop so the first socket is a half-pin from the shoulder of the rabbet. To determine how thick the spacer must be. subtract the width of the drawer-front rabbet from Vs inch, which is the center-to-center spacing of Winch dovetails. That Winch rabbet calls for a Winch spacer.

Rout the sockets in the drawer fronts first. Clamp the positioning scrap in the jig in place of a drawer side. Set the spacer against the alignment stop, then set the drawer front in the jig, as shown in Rabbeted Dovetails. Butt the end against the tab of the positioning scrap, the bottom edge against the spacer. Clamp the front, then rout the sockets.

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Responses

  • mylie
    Does the bit matter for half blind dovetails?
    6 years ago
  • faith
    How to set up a haifblind dovetail jig?
    4 years ago
  • zahra ambessa
    How to router half blind dovetail joint on different diameter wood thicknesses?
    2 years ago

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