Pins or Tails First?
This was the title on the first issue of Fine Woodworking in 1995 I ever bought, where two experts, Frid and Becksvoort debated which method was the best. Before I even cut a dovetail, I knew that this was a debate that was likely never to have a definitive answer. What I did know, was that cutting dovetails by hand (or at least without a router template), was a part of the craft of furniture making that you can always work on. THis current project is the largest case I have ever attempted to put together with full (through) dovetails.
Layout of the Pins
I prefer to cut the pins first simply because this is how I was taught. I also think that transfering to the tails is easier with a long board of pins. At a recent woodworking show I noticed a trend of cutting dovetails (especially the pins) with really thin pins is what everyone is looking for. While cosmetically, this looks nice on drawer sides, It just isn't very practical or strong for a case piece of this size, and while still an amateur at cutting dovetails, one wrong move and there goes the pin. I scribe a layout line along the edge of the boards about 1/64" thicker than the thickness of the board stock. This allows the pins and tails to extend out over the edges of the boards slightly after glue-up. This can then be easily trimmed flush with the surface of the board. I layout the lines with a handy 1:6 ratio dovetail layout tool, and make the pins on the outside edges about 3/8" thick at the thinnest section, versus 1/4" of the inner pins. I also transfer the layout lines against two boards at a time to get evenly spaces tails on either side of the case. I then cut to just shy of the pencil lines with a Japanese Dozuki back saw with a fine kerf.
Once the I've cut to just shy of the scribe mark, I layout the boards on my bench with a reference board to guide my chisel and hammer hits square to the line. I alternate hammer strikes down along the scribe line, and then more gently pare out the waste across the end grain, to just about 2/3 of the way down the line of the pins. I then flip the boards and follow the same steps to remove the remaining waste. This waste produces a really nice pile of thumbnail-sized chips, as seen in the first image in this blog entry. I then lay the tail board flat on my bench, and place the pin board perpindicular to the tail board. Then, I'll scribe pencil lines against the inside edge of the pins onto the tail board. Cutting the tails with a hand saw is one option, but I prefer to cut the tails on the band saw. This keeps the cuts square, versus slightly straying when cutting by hand, which I tend to do. Cutting right to the lines on the bandsaw gives me a pretty decent fit right off the saw. I then use a small mill file to shave away a little bit of the pins to get the fit just right. I discovered this technique, versus pairing with a chisel. I have always run into splitting issues when the grain gets tricky, the mill file removes small amounts at a time, safer, and without the risk of taking away too much.
Glue Up w/ Lots of Clamps
After doing a dry fit of all the parts, I check for squareness and prepare everything for glue up. I needed to borrow a few extra long clamps from a relative in town in order to get enough clamping pressure evenly applied to the piece. I then cut some glue blocks that have a gap left over the ends of the pins, so the only contact along the clamping surface is agains the tails. This pulls everything in nicely during glue up. Get all of the clamps and pieces layed out close by and I apply glue along all of the glue surfaces.
Clamp up is a frantic activity for a piece this big, a big block of wood and a rubber mallet drives everything home, and then I get the clamps all tightened up. I then check for squareness again, and push the corners into square with a little muscle. I checked everything out in the morning and remove the clamps. Success, and another woodworking milestone reached.
Base Design and Filling Some Imperfections
Next post I'll be playing with some prototypes of the base design of this case as well as experiment with Gorilla Glue's new two-part epoxy and cherry sawdust to fill some knot holes.