A few instructions can save hours of head scratching - so here are a few instructions.
What are you waiting for!
Before laying out any dovetails, you need to prepare the ends of the two boards that are being joined. Because the sides slope
A few instructions can save hours of head scratching - so here are a few instructions.
What are you waiting for!
Before laying out any dovetails, you need to prepare the ends of the two boards that are being joined. Because the sides slope, finding the correct angle to cut the ends takes a little geometry. What's more, it's not just one angle, but two! So take a deep breath, and jump right into the next step.
Grab yourself a large piece of paper, and draw an accurate elevation (front view), with an aligned plan (top view) a little way underneath.
First we'll find the width of the squared four sides stock you need to start with. On the drawing, extend the inside face of the side running in and out of the paper upwards. Now draw in a line that runs down, perpendicular to the extension, which connects to the top, outside edge. (The picture explains this much more clearly!) Now you can measure off the full width, as shown.
It may seem strange, but you can't simply measure the length of the board required from the top of the elevation, thanks again to the sides sloping. But don't worry, it's not too difficult. Draw in a line, parallel to the top, from the point that gave the full width, out past the end. Then extend the outside face of the side to meet it. Now you can measure from this new point to the opposite end of the elevation. REMEMBER to construct a similar point at the other end first, if that is angled too! Again, the picture explains this better than words.
The angle which you cut the face of the boards needs to be found now. There is a little more going on to find this, but again, the picture paints a thousand words. Rotate a copy of the side in the elevation (the one going in and out of the page) 90°ccw. The corners of this copy can then be projected down into the plan, intersecting with the top and bottom edges of the inside face of the rear side (extended towards the left). These four points of intersection define a true, flat, view of the end of the side, from which the cut angle can be directly measured, or transferred to a bevel gauge.
One last angle to find before we can prepare the sides. In the previous step, we constructed a true, flat, view of the end of the side. By intersecting this at right angles, with two parallel lines that are the true thickness of the boards, the diagonal between the intersections gives the bevel angle of the joint edge. Without this bevel, the joint would have a gap on the inside when the parts are aligned at 90°, due the way the angled end issloped. Try it and see for yourself.
Cut each side to length, with the true end angle(s). This is easy with a back saw, or miter saw. Prepare an angled auxiliary fence (90°minus true end angle) for a shooting board to shoot these accurately.
To bevel the ends, either plane freehand using a bevel gauge to check, or make a ramp (90° minus the bevel angle) to add to the shooting board setup.
You can't use a normal dovetail template, because the angled ends throw the alignment out - the resulting tails would have one steep and one shallow side, leading to an odd looking and weak joint. Instead, each side of the tails are laid out at the same angle to lines drawn parallel to the side's length.
Before spacing out the pins and tails, use the bevel gauge, set at the slope angle, to mark the bevels that will be made later to level both top and bottom of the sides.
Then mark an allowance for this on the face of the sides. This will a