The Half Lap Dovetail
The head board is a vital component to the over-all design of the Platform Bed I'm in the middle of building. Visually and aesthetically, the top of the head board can make a good design great, or a mediocre design poor. I chose to show-off some joinery here in the form of a half lap dovetail that will join the uprights to the top rail. The wood is Black Walnut. The two uprights are finished at 4' wide by a heavy 7/8" thick. They'll be joined to the head board rail which is also 7/8" in thickness by 5 1/4" wide.
Surface the pieces being used making sure they're flat and square. From my Power Planner I go over the entire surface with my 5 1/2 Bench plane. This takes down the high spots and sets things up for smoothing. I follow with my #4 Bronze Bench Plane that incidentally has been working like a dream as of late. Funny thing these hand planes; some days they're cranky and chatter like an old junk yard dog and other days they purr like a sweet little kitty.
Scribe the Cheeks
To make this joint work, the first step is to establish the depth of the cheeks. These will be cut out of the width of each mating surface so when the finished joint goes together, the surface will be flat. I determine the center of each piece and scribe a deep line with my marking gauge. The deeper the better here so our saw will have a good reference mark to follow. Mark the pieces up from the shoulders, across the top and down the other side making sure not to mark the faces. The depth of the entire dovetail is simply the over all width of the mating piece. I mark this line as well, again being careful to keep the show side free from any lines.
Cut-out and Fine-Tune the Cheeks
Cut out the cheeks with what-ever method you see fit. A clean Rip saw would be my first choice, however you could set up a dado at the table saw and cross cut the back side of the upright to remove the waste to the determined depth. Or, perhaps at the band saw. What ever way you choose be sure not to cut down below the scribe marks and once finished, clean up the shoulders and the cheeks. I use my Medium Shoulder Plane as well as a long, freshly sharpened chisel to smooth out and fine tune these areas. In the photo below you'll notice my grip on the chisel, this is actually the second part of the paring process. I first make a shallow cut using my thumb on the back side of the chisel; then I follow with this full fisted grip while controlling the forward movement with my right hand. It's a safe way to work while keeping maximum control over the tool.
Determine the Slope
I use my Bevel Gauge to lay out the dovetails for this joint. Seeing as I'm using a hardwood in Walnut, and this is a kind of decorative, over-sized lap-joint I'm cutting; I chose a 10 degree slope for my dovetail angles. Now before I start to try to justify why I chose this particular slope let me say it is purely visual. If you'd like to discuss dovetail slopes; they're history and heritage, please write and we'll have a go. If you'd like to read a bit on some of the reasons why some craftsman use a 7 degree slope while others can use up to a 14, as well as everything in between, check back into Chris Schwarz' Blog at Lost Art Press for a great article on Dovetail slopes.
Scribe and Cutout the Dovetails
Again we have some choices here. Once we scribe the dovetails with a deep, clean cut with a marking Knife, we need to cut out the dovetail. A finely tuned Rip-saw is my first choice however, a Band Saw will also work fine. Clean up the edges with a chisel or what I used this morning for this was the spare blade out of my Jointing Plane. It's a nice big 2 1/4" Bevel-Up Iron, 3/8" thick. The massive size made it easy to register flat on the edge of the narrow dovetail slope to clean up any saw marks left behind. I also used a chisel in the corners. Keep in mind the sides of this joint have to fit into the half lap, so if anything, make them bevel so the show side, or face is a little wider than the back. This will help ensure a tight fit later.
Fine Tuning the Shoulders
Try a test fit on the head board rail taking careful notice of where the shoulders meet. This is a critical area that can make the joint work, or make you look like an amateur. I use my Shoulder Plane to clean things up taking a light cut and coming in from each end. Taking a full shaving over the entire width could lead to a split on the opposite side of the upright. I get in tight and finish off with a well honed chisel.
Transferring the Lines
I lay out the rails and carefully mark the perimeter with a pencil. I then take my bevel gauge and determine the slope. This may be slightly different than the first from when we cut it out.
As well make sure you mark the left side as well as the right seeing as there's a real chance that they're not exactly the same. When we cut out the waste for the socket, we'll need an exact fit!
Cutting Out the Socket
At this point we have our lines nicely scribed with a clean, deep knife line. Before I start to remove the waste I take a large chisel, in this case 1 1/4" width, and follow the knife line with a slight bevel cut.
Keeping the Chisel on the waste side, I'm careful not to disturb the tiny shoulder established by the marking knife. This shallow "V" groove will act like a guide for my saw when we cut out the waste.
The Tenon Saw
I use my Large Tenon Saw to make a series of cuts through the waste area. I'm careful to stay away from my scribe line telling me the depth I need to remove. This is a great time to practice hand sawing and I first lay out a series of pencil lines with my square and follow along. Remember, practice makes perfect.
The Router Plane
Once I have my saw lines cut, it's an easy job to remove the waste between. I use my large Router Plane with the full 1/2" cutter installed. Shallow passes assure I won't tear out any fibres on the opposite end of the socket. I clean up the edges with a chisel and try a test fit. Making sure the dovetail sits down into the socket before making any adjustments.
Next I'll be inlaying two solid Walnut Butterfly Joints into the side rails of the bed and attaching the head board. Stay tuned...