Sliding Dovetails by Hand
Sliding Dovetails Require Great Precision
I cut the pins of the sliding dovetail first and really this is less a dovetail joint and more of a dado or housed joint. The pin is cut exactly the same as a dado with a saw to create the sides, a chisel to roughly remove the waste, then a router to finish and refine the floor of the joint. The different here is setting the 12 degree angle for the walls of the pin. I use a sawing fence with a 12 degree angle on one edge and it makes the sawing really simple. Just keep the saw plate pressed firmly against the fence and voila! You get perfect sliding dovetail pins.
Cut the Tails with a Chisel Using the Same Fence
Once you have sawn the pins, the fence can then be clamped in a vise and used as a paring block that shape the tails. I will saw the shoulder of the joint in order to sever the fibers and then you can quickly pare away the small amount of material needed to shape the tail. I do demonstrate using a rabbet plane or a shoulder plane to speed up the process a bit but in the end the paring fence is used to create the final angle and get right up into the acute inside corner.
I do demonstrate a dovetail plane it is obvious that if you do a lot of longer sliding dovetails in your work that a sliding dovetail plane is a really life saver. It makes the process faster but also adds a lot of precision when it comes time to fit the joint.
I prefer the ease of layout and cutting with a consistent width dovetail. While tapered sliding dovetails are easier to fit I find that a compromise can be struck by imparting a slight taper to one side of the tail to ease the fit up until at least the halfway point of the joint. To be clear, it is less of a taper and more of just a couple thousandths of an inch narrower at the back of the joint. The goal here is a hammer tight fit but that hammer tightness only kicks in at the last 4-6" of the joint.
Making a Square Case
Near the end of this live broadcast I got a question about how to make the shoulder to shoulder dimension of the dust frames I was dovetailing into this case so I took that opportunity to talk about making square cases and how ganging together your parts for layout ensures that things stay square and you get perfect shoulder to shoulder dimensions for rails, case sides, dust frames, etc. The key is turning variables into constants and relying on those constants to shape all the additional parts.