Secret Dovetails for the Rest of Us
I hate end grain. In my work, I take great pains to hide every square inch of it. This often means cutting joinery that is more involved. For example, on my spice chest, I could simply have used through-dovetails to join the top to the sides of the case. Like the original maker, I chose a slightly more difficult half-blind dovetail. Why? Even though the cornice would have covered up the visible end grain of the pins when seen from the side, the end grain of the tails would have been visible on the top of the case. With that, I just can’t abide. But what are you supposed to do if you are making a joint that won’t be hidden in any way by a moulding? You’ll need to cut a secret dovetail.
The secret dovetail, also called a mitered or full-blind dovetail, appears to be one of the most difficult joints to cut successfully. However, I find it a little easier to do than a good through-dovetail. Instead of having to pare (or peen) many parts to perfection, there are only three show surfaces on the secret dovetail: the top and bottom edges and the miter itself. The interior can be as gap-toothed as a beaver with a meth habit as long as it is structurally sound and the three miters are tight. Only you will know what secrets the secret dovetail hides.
Secret Dovetail Layout
This technique for cutting the secret dovetail only works when joining boards of equal thickness. The first step is to set a marking gauge to the thickness of your boards. Referencing the end grain, scribe a line on the inside faces of your boards, and also on the top and bottom edge of each. Take a straightedge and connect the outside corner of the board with the corner created by the inside edge and the scribed line. This will give you a 45° angle across the long grain. This must be done on each edge, so four times total for one joint.
Now, set a gauge to approximately one-third the thickness of your wood. Here, I’m using 3/4″ pine, so I’ve set a gauge to 1/4″. This particular board is horribly soft and the grain tears out badly even with very sharp tools, so I had to make my lines very carefully to avoid ripping out the grain. On each board, make a line on the end grain and both edges with this setting, referencing the face side of the wood. Now, set a gauge from the end grain to the point where the 1/4″ line intersects with the initial 45° line and scribe a line down each edge and on the inside face referencing the end grain.
Pin the Tail on the Rabbet
Saw, chisel and plane the rabbet so that you have a 1/4″-wide tongue at the outside face of the board. Proceed to lay out your pins in your chosen manner – but only in the rabbeted area, leaving the outside tongue untouched. Note that you must do pins-first here, as there would be no way to scribe the pins from the tails if you did tails-first. Remember when laying out that you will cut away most of the outside half-pin, so you will need to have a few more pins on the inside than you might think necessary for a small joint. A little over-cutting on the pins goes a long way, because you can’t saw out the waste on the secret dovetail; you have to chop them. Lay out your tails from your pin board. This is very easy, as the rabbeted tongues act like an extreme version of the “140 trick.” Then carry your lines square across the end grain. As always, mark the waste before cutting anything. Saw and chop the waste, cutting on the waste side of the line.
And now the Miters
Next, you must cut the miters on the corners to a tight fit. You scribed the miter on the long-grain edges during layout, so now you just saw all four of them, leaving the whole scribe line. This will give you a little “meat” to pare away to a tight fit. Once you have your edges cut, pare away the waste that remains at the edge of the long miter. I use a chisel for this, followed by a shoulder plane. It is key that you don’t chisel or plane away the “knife edge” of the miter while fitting, or you will be left with a ragged and ugly edge. It’s a good practice to use a miter jack for this, if you have one. Either way, pare and plane small amounts, testing the fit often, until you have a tight-fitting, good-looking miter on the two long-grain edges and the front edge. Clamp up the dovetail to check the fit of your newly cut secret dovetail.
The secret dovetail may take a little more time than a normal dovetail (this example was done in about 30 minutes, hence the ding in the baseline end grain of this terribly soft board). But it is worth the extra time when you are doing especially nice work, where the look of end grain will ruin the piece or where you can’t simply cover it up with moulding.
Click on the photos below to make them larger.
– Zachary Dillinger, contributor
• Looking for more great instruction on hand-tool approaches to woodworking? Check out “Hand Tool Essentials,” a collection of articles from Popular Woodworking – available now in PDF format for your computer or PDF-enabled eReader, and also available in print (paperback book). And don’t miss Christopher Schwarz’s 2-DVD set, “Mastering Hand Tools,” with video instruction on using the tools every craftsperson should know.
Editor’s note: We’re inviting our contributing editors and authors to write blog entries for us on all things woodworking – particularly related to articles they’re writing for the magazine. The post above is from Zachary Dillinger, a talented woodworker who works only with hand tools as he makes bespoke furniture in his Michigan shop. You can find out more about his work (and read his blog) at Eaton County Joinery. His William & Mary spice chest will be featured in an upcoming issue of the magazine.