Cutting dovetails by hand is often more time effective than setting up and cutting dovetails by machine, unless you've got more than half a dozen drawers or other pieces to do. Hand-cut dovetails also enhance the piece in ways that are difficult to define, but definite in effect. A little practice is certainly needed, but the tool requirements are fairly low, and the steps are easily followed.
By following these steps and practicing, you can become proficient at cutting dovetails by hand.
Tool needs: A marking gauge for scribing precisely located lines parallel to the ends of the boards, an angle-marking gauge or a sliding bevel, a saw to cut the dovetails, chisels, a straightedge and a pair of clamps to hold the straightedge and the work tight to your bench, and a marking knife. You can use almost anything to make your marks, but nothing does a better, more accurate job than a good, sharp marking knife. You may also want a small--no more than 1-1/2 pound--mallet to drive the chisels.
Most projects that use dovetails are constructed out of hardwood. That is the drawer fronts, doors, and face frames are hardwoods; small boxes, and large, are often completely made of hardwoods. Drawer sides are often made from a hardwood called poplar because of its low price and the fact that it is very easy to work. I suggest that you use poplar for the tail and pin boards while you are learning to cut dovetails. Using a hardwood gets you used to the way hardwood reacts to cutting tools. Poplar is actually easier to work with than most pines and firs.
Hand-cut through dovetails can be made in any size or spacing desired. Let's assume you are using 3/4" thick stock, so the pins need to be 3/4" thick at their widest point. Good mark-up is the most important part of the job. Without good outlines, the joints fail before they are cut.
Use your marking gauge to measure the thickness of the piece that is to have the tails cut into it (set the gauge as you measure so that the measurement is a small fraction more than the actual board thickness, say 1/64"). Scribe a line on all four faces of the board that is to have the pins cut on it; this line extends across the end of the board. Deciding just where to put the individual pin marks is probably the most trying part of the job. Measure from both ends of the board: Most of the pins can be the same size, but end pins may be narrower in order to fit the space (since they are half-pins anyway, they are easy to adjust). Adjustments in size may also be made in interior pin widths, further enhancing the hand-cut look by their variation from the other pins and tails. Don't forget, though, that any resizing of a pin requires a similar resizing of its matching tail. Dovetail gauges (also called dovetail markers) can save time: these markers have sides set at the correct slope for the pin or tail sides.
If you're using a sliding bevel, remember that the pin and tail ratios are about 1:8 in hardwood (this is an approximate figure that can range from 1:6 to 1:9 without creating problems, but it must be the same for all parts or nothing will fit).
To get a 1:8 ratio, measure up the board (with the grain) 8" and measure in from the 8" end 1". Draw that line down to the base of the 8" line, and you'll have your 1:8 slant. Set the slant on your sliding bevel, lock that tightly, and mark at the particular pin widths desired.
To get even spacing on any board, use a rule at an angle. Pick a rule length longer than the board is wide, and tilt the rule so that the start and the length are both on the board edges. Then mark at the inch increments on the rule. Each space is equal. The steeper the tilt of the ruler, the less wide each marked space is. A bit of experimentation allows you to get almost any spacing measurement you wish.
Then, use your dovetail gauge or sliding bevel to mark out the pin spacing on the end of the board. The pins at the ends of the boards are called half-pins because they are only angled on one side. The actual size of the half-pins is often about the same as the rest of the pins. Size and spacing of the pins is largely a matter of personal taste. Small pins look nice, but they are harder to make. When you are first learning to cut dovetails, it is good practice to make the widest part of the pin equal to the thickness of the stock. The tail between the pins should be equal to or larger than the pin in width. Vary the spacing to get even spacing between the pins. Mark the waste sections with Xs. You can get all your marks set with the pins, then cut the pins and use them to mark the tails.
Saw on the waste side of the lines just down to the scribed line with whichever type of saw you use: A gent's saw, a dovetail saw or any of several other small, thin bladed backsaws may be used, as may a Japanese dozuki saw. For some lower cost dovetail saws, you will want to remove the tooth set and re-sharpen before using the saw to cut dovetails (this is not an essential to early practice, but does ease the cutting in hardwoods…and it can sometimes be done with just a gentle touch of a diamond hone on the sides of the teeth). Removing the set turns the dovetail saw into more of a rip saw, which it needs to be. Look for a saw that has at least 14 teeth per inch, with more being preferable, rather than less.
Before you proceed with the dovetailing, check to make sure your chisels have been sharpened and honed. The next step is much easier with sharp tools: Damage to you or your project is also less likely if you use sharp chisels, because you can then guide the chisels, not force them. Before you begin cleaning out the waste, clamp the board onto the edge of your bench with the straight edge locked exactly on the scribed line. Chisel out the waste stock using the clamped-on straightedge as a guide. Using different sizes of chisels may make this job easier. Work across the board vertically, from left to right. Then, work from right to left, removing waste stock from each area by tapping the chisel into the waste horizontally. Next, follow this with another round of vertical cuts. Remove the chips with horizontal cuts. Continue this until you are just over halfway through the board. Repeat this procedure on the other side of the board. The straight edge helps to ensure that the cuts are square or perhaps slightly concave on the chiseled edge; a convex surface doesn't work here, because it causes gaps.
Mark out the tail piece as soon as you have cut all the pins. Stand the pieces at right angles to one another, and scribe the exact size and shape of the pins onto the uncut tail board. Again, mark X’s on the waste areas. With these pieces, it is especially important to cut on the waste side of the line.
After you have cut to your fresh scribed lines, again remove the waste stock exactly on the tail pieces, with first vertical, and then horizontal chisel cuts.
If you have marked out carefully, your dovetails will go together with little or no fitting, and very little force. Sometimes you may find that one or more of the tails may be too big or too small for the pin. If you cannot have a perfect fit it is better to have a tail that is too large so all you have to do is pare it. Use a freshly honed chisel to remove any excess wood that keeps the joint from fitting; ensure that the pins and tails fit loosely enough so that you need not hammer the joint together, and fit tight enough that the joint will hold together without glue. In fact, if a hammer is needed to test fit the joint, you are in trouble. It can sometimes prove impossible to disassemble such joints for gluing. Before forcing a fit, pare carefully, test fitting as you go. This is going to take some extra time with the first few hand cut dovetail joints, but with practice, your joints will fit better, and easier, without extra work.
If there is a gap between the pins and tails, your next step depends on the size of the gap. If the gap is narrower than the thickness of the kerf of your dovetail saw, go ahead and glue the pieces together; you can solve the gap problem after the glue has set by injecting more glue into the joint.
Gluing is a straightforward part of the operation. Using hide glue in a glue pot can be fun, but almost any good quality wood glue works, including the aliphatic resins (PVA) and liquid hide glue. For joints that might be subjected to damp conditions, the newer polyurethane glues are excellent, but need to be placed on only one surface of the joint. With other glues, cover all mating surfaces. Clamp the pieces together, check to make sure the assembly is square and all the pieces are perpendicular to each other. With hot hide glue, by the time the glue has cooled to room temperature, you can unclamp the joint. Other woodworking glues require anywhere from 30 minutes to an hour of clamp time.
Patching is a topic that is rarely discussed, but most woodworkers make mistakes, and should learn how to hide them so they are not so noticeable. While your glue is setting, try to pull a small piece of veneer through the gaps; if it is too tight, make a saw kerf through the glue. This can make a small mess, but it works. Just make sure you wash the glue off the blade immediately after this operation (it helps to dry the saw, too, possibly with a light wax and buff when the session is over). Then put glue on both sides of the veneer. Most veneer is the about same thickness as the kerf of the average dovetail saw. Dovetails can be patched this way with a contrasting wood, to add a decorative effect.
If there are still void spots on the joint, you may want to inject some more glue into them, after mixing in some sawdust from one of the cuts. Also, it is a good idea to start cleaning up while the glue is still about the texture of cottage cheese. Cleaning up this joint can be as easy or as difficult as the woodworker wants it to be.
If pins and tails extend a fraction of an inch past each other, sanding or planing (with a low angle plane) carefully smoothes things for a perfect finish.
It takes roughly 15 to 45 minutes of total practice to learn to hand cut through dovetails, with each pattern (half-blind, etc.) adding another 15 minutes after the through dovetails are mastered. Then it takes minutes or less to set up for cutting dovetails on a new drawer or box or a short series. Machine cut dovetails are great, but setting up can take as much as 40 minutes with some jigs, which means you can have everything cut, and the tools put away, doing the job by hand. It's certainly worth a try, for two reasons: it's fun and it gives your work a look of craftsmanship available in almost no other way.