Shop Supports – Learn to Cut Three Joints by Hand
by Bill Anderson
I have used what I call “shop supports” for many years. These are not sawhorses, and they are not outfeed tables – they’re somewhere in between, and I find them indispensable.
I use them to temporarily store and sort lumber that I get in for workshops I teach at the Woodwright’s School. And when I process stock, the shop supports are tall enough that I do not have to do a lot of bending over. The shop supports are just high enough that I can comfortably crosscut or rip stock by either clamping it or holding it with my off hand.
Two supports provide stock support; one provides offcut support. I also find that the three supports, when overlaid with a panel, make a useful temporary bench. Recently I made new shop supports, primarily because the feet had rotted away on my old ones, but also to eliminate the nails and screws and instead rely on strong joinery.
I used 2×6 pine from the home center. For three shop supports, I needed three 10′ boards (for the tops and stretchers) and one 12′ board (for the legs). I planed and trimmed it straight, square and flat, to a common width and thickness. The lengths on my pieces are 42″ for the tops, 24″ for the legs, about 31″ for the stretchers and 18″ for the feet.
I used three joints for assembly. The feet are joined to the legs by half-laps; the stretcher is joined to the legs by wedged through mortise-and-tenons; the top is joined to the legs by through sliding-tapered dovetails.
My final shop supports’ 261⁄2″ height is not a magic number – it’s the dimension that fell close to 2′, which is a good compromise between bench height and sawbench height. The 42″ length of the tops is primarily because when I was cutting 4′ x 8′ plywood, this left 3″ all the way around for clamping straightedges to the sheet goods when sawing it.
Before moving on past dimensioning your stock, mark the reference face and edge (a flat, straight face and flat straight edge that meet at 90°) on each workpiece. You’ll do all the layout referencing your tools off of these surfaces.
Tapered Sliding Dovetail
Tapered Sliding Dovetail I constructed these shop supports by starting at the top and working down. The sliding dovetails have to be fit first, because the width between the legs determines the length of the stretcher. In general, I make the wide part of the tapered joint on the backside (if there is one) so that if I have to whack on the joint to drive it home (not ideal), any damage is not so visible. The sliding tapered dovetail is a straightforward joint, requiring no measurements other than using simple layout tools adjusted by eye, with some consideration taken for proportioning.
There are two rules for these joints: the “Rule of Halves” and the “Rule of Eighths.” The Rule of Halves states that whatever degree of taper you choose to use translates as a gap in the joint just before you begin the assemblage; for each halfway assembly of the joint, you reduce the gap by one-half. So how many halfway steps do you need to reduce the gap to an acceptable amount? A slight taper means that the joint closes up quickly (not many half steps), and you might need a sledgehammer to knock it home. A heavy taper means that the joint closes up slowly, and it could be too loose and pass all the way through. The Rule of Eighths states that a taper of 1⁄8″ over a width of 8″ means that three halfway steps will reduce the gap by a factor of eight (2³, to 1⁄64″ in this example), and one more halfway step will close the joint (in the last eighthwidth of the stock). You can apply this rule to any width of stock, adjusting the taper proportionately.
First, lay out the tail portion of the joints on the top of the legs, then transfer your marks to lay out the socket on the underside of the top, about 6″ in from the ends. The reference edge of the top is the one you look at and the reference face is the underside of the stock. The tail height should be more than one-half and less than two-thirds the thickness of the stock into which it will slide.
Also mark the sockets on two edges of the top, referencing from the underside. I like the joint to have two shoulders to rest on. One shoulder is a rabbet, the other is the dovetail. This helps to square up the joint during assembly because there are two shoulders for it to bear on.
I make the tapered dovetail shoulder on the leg in several steps. First, I cut a square ramp with a saw at the baseline and on the end grain (and clean it up as needed to square and straight with a chisel and shoulder plane). Then, I saw the shoulder deeper to create the dovetail shape, and remove the waste with a chisel to clean up the angle.
You’ll note in the pictures that I laid out and cut the straight shoulder for the socket as I did the tail. But if you’ve not already done so, lay out the square lines to define the rabbet shoulders, then saw these shoulders. Turn the top upside down, and place the leg upside down with the rabbet on the leg set flush to the shoulder cut on the underside of the top. With a pencil, mark the tapered edge along its length. Remember, this will be the full width of the tail. Knife in a second line 1⁄8″ inside this line (the same offset you sawed into the leg). This denotes the width of the neck (the narrow part) of the dovetail. On the two edges of the top, draw in the dovetail angles by connecting the knife line to the pencil line, using a bevel gauge. Saw the knifed shoulder line down to the gauge line. Remember to saw in the waste side, up to this knife line. This is important and the only absolutely critical aspect of this joint.
To remove the waste, make a saw cut straight down the middle of the two shoulders for relief, then pare out the majority of the waste with a long, thin paring chisel. Clean up the bottom using a router plane with a narrow spear-point blade (set to your baseline).
The joint should assemble easily seven-eighths of the way in – but don’t push it all the way together yet. If the joint is too tight, either the neck is thick, the tail is wide or the taper is not even. If the joint does not bottom out, it is likely a neck problem. If the visible gap during assembly is not even top-to-bottom, then the angles do not match and the tail is probably too wide. Use a small straightedge to ensure that the taper is even and flat along its length, and to check for high spots, then adjust as necessary.
This article first appeared in the February issue of Popular Woodworking. Get your copy and continue reading!