Edge-to-Edge Joinery – more:
Rob Porcaro covers shop-proven techniques for producing accurate joint surfaces and aligning them for glue-up.
Rob Porcaro covers shop-proven techniques for producing accurate joint surfaces and aligning them for glue-up
The fundamental simplicity of the edge joint demands accuracy. There is no mechanical lock and even tiny gaps are visually and structurally unacceptable, and the finished joint is fully exposed. No problem – here are techniques for success.
The task at hand
As discussed before the joint edge of the board should have just a slight camber (concavity) along its length, there must never be the slightest convexity across its width and, when the camber is closed with only mild pressure, the edges should fully mate along their entire length to produce a flat panel.
Hand planing has no equal in producing these requirements while creating an ideal surface for gluing. A small-shop woodworker can efficiently produce quality joints by using a well-tuned jointer or tablesaw to bring the edge close to ready, and then add the critical elements with a hand plane. In this way, you can produce edge joints that the most sophisticated production machinery cannot match.
The same excellent results can also be achieved without any machinery, working from a hand-ripped edge. It just takes longer and there is more opportunity to temporarily go astray in accuracy.
You can work to a higher standard than any machine operator
The tools at hand
Essential equipment for all but small work is a long plane to bridge the valleys and level the hills to produce an accurate edge. I prefer my #7 jointer, 22in long with a 23⁄8in-wide blade, while some like the beefier #8 at 24in long with a 25⁄8in blade. For long grain shooting of boards up to about 600mm, I like my boxy, heavy 11in #9 shooting plane, but a regular bench plane will do as well.
It would be difficult to overstate the importance of sharpness in producing accuracy. The edge of a dull blade gets excessively deflected into the wood, which reduces your control of the shaving thickness. A sharp blade can take thinner shavings with less blade deflection and less pushing effort, and thus afford finer control in adjusting the joint edge.
Plane soles for comparison, from top to bottom: #4 smoother, 11in #9 shooter, 14in #5 bevel-down jack, 15in bevel-up jack, 22in #7 jointer
Living on the edge – without a jig
This time-honoured technique can be called the camber shift method. Set up the plane by centring the depth of the blade camber across the width of the sole. The amount of camber is closer to that of a smoothing plane than of a jack plane. In use, make corrections to an out-of-square edge by shifting the plane laterally to let the camber depth take down the high side.
You are shifting, not tilting, the plane to make these corrections. Maintain the flat orientation set into your muscle memory from countless hours of planing board surfaces with, of course, the sole parallel to the bench top. Take advantage of this embedded physical pattern by securing the board properly vertical with its edge only an inch or two above the bench surface. This will also help your eyes sense the plane sole parallel with the bench top. I like a broad grip with my forward hand to feel the overall plane balance, with fingers tucked under the sole to register the lateral position.
With just a little practice, it is fairly easy to correct an edge that is consistently out of square along its full length. It is more difficult to snake the plane left and right to take down particular sections of the edge that are high. You can mark the high spots but, unfortunately, the marks are covered by the big plane several inches ahead of where you want the blade to engage them. This method involves repeated checking with a square, estimating the amount to be removed and rechecking. It helps a lot to start with a good edge from the machine (which is, after all, a jig).
The front hand helps to sense flat and guides the lateral position of the plane, as it applies variable downward pressure during the pass
This makes it easier
This method has worked for me for more than 30 years. I have tapped three 10-24 (about M5 x 0.8) threaded holes in the side of my Lie-Nielsen #7 (and the same in a Record that preceded it) to accept a simple, two-part wooden fence that registers the plane sole square to the side of the board. The inner part of my trusty fence, which contacts the side of the board, is 280 x 45mm. Commercial models have become available.
The blade is slightly cambered to prevent any possibility of convexity across the width of the joint edge. I sight down the sole from the front of the plane to set the blade to a symmetrical projection just in the working area (e.g. 19mm) adjacent to the fence. Though this method does concentrate wear in a portion of the blade, you can save a trip to the sharpening bench by swapping out the inner part of the fence with one of a different thickness, or simply applying an additional piece with double-sided tape.
I apply pressure to the fence with four fingers while my thumb applies variable pressure to the top of the plane near the knob. I initially concentrate on getting the edge square, then work on producing an appropriate camber along the length.
This fence is simple to make
The front hand maintains pressure on the fence against the side of the board, as it applies variable downward pressure during the pass
Thin boards are another matter
It is difficult to freehand balance the plane on thin stock, usually less than 13mm, and the fence method tends to distort the workpiece. This work is usually not more than 600–750mm long. The solution is to lay these boards flat and shoot the edge with the plane on its side. Long grain shooting is so easy, yet seems to be underutilised by many woodworkers.
I usually use my long shooting board for this. The end stop helps stabilise the workpiece, and the plane rides on a slick plastic surface. Even simpler, you can dog a support board in place on the workbench, and then place the workpiece on the support with the edge slightly overhanging.
To negate any slight discrepancy from square in the setup, place together the two boards to be joined, then close them like a book, and present each edge to the plane in that orientation. Only for thin boards, I use my #9 shooting plane with its usual straight blade edge used for end grain shooting. A bench plane with a slightly cambered blade also works well, but centre the camber depth where the blade engages the workpiece. For shorter pieces, I like to use a grippy glove on my left hand, but longer pieces should be stabilised with clamps.
The grippy glove, along with the front stop, makes it easy to control the workpiece
Two at once?
It is sometimes suggested to plane two edges at once in a closed bookmatch orientation as an expedient way to get out-of-square errors to cancel. This can work well for shooting thin pieces, such as small drawer bottoms, with a straight blade edge. Align the edges and clamp the pair on the support board.
The two thin boards can also be held together in the closed bookmatch orientation in the front bench vice. However, when using a bench plane with this setup, the blade camber should be minimised. With thicker boards, say 19mm, and using your jointer plane prepared with a typical camber, an inherent error in the process becomes significant.
Two 9mm pieces are aligned, clamped and then planed together
With each method
Save a lot of trouble by evaluating the initial condition of the edge to be planed with a straightedge and square. To produce the joint camber, start by taking a thin shaving or two from the middle of the length of the board, easing the plane in and out of the cut. Sense how the blade is grabbing the wood.
The length of the early passes should be shorter if the edge is initially convex or is suspect. On shorter boards with a long plane, you may need to continue in the interior of the length until the blade no longer engages. If the edge is nearly straight to begin with, make the initial pass longer. Progress by lengthening successive passes at each end, keeping the shavings thin.
Finish with at least one full-length, full-width, thin shaving to ensure there are no localised bumps or troughs. On longer boards, it is easy to overdo the camber, even with a jointer plane. If there is too much camber, successive full-length shavings can reduce it.
Use good basic planing technique to avoid dipping the plane at the beginning and end of the board. Exert pressure on the front hand going in, on both hands in the middle and on the rear hand going out.
With practice, you will sense when you have produced a good camber, even before you test it
Aligning the boards into a panel
Especially for a small-shop woodworker, it pays to minimise the work and loss of thickness involved in flattening a glued-up panel. Using biscuits to align the boards is an easy way to accomplish this. They are not needed to strengthen a good joint but they won’t hurt.
For this work, I do not use cauls, complicated over-under clamps, pinch dogs, dowels, Dominos or splines. I also do not like hammering glued, partially clamped boards into alignment. Time is limited during glue-up, and I would rather not rely on a hit or miss method.
For 19mm stock, I use #20 or #10 biscuits, and #0 for 13mm stock, typically 200–300mm apart, and about 50mm in from the ends. The biscuit joiner’s fence must be set accurately square to the blade slot face. Secure the board with its edge overhanging the bench top, and firmly press the fence down against the face of the board as you advance the blade. Even for ‘standard’ 19mm stock, this is faster and more accurate than trying to tightly register both the board and the joiner sole against the bench surface.
Working with thin boards, such as a 9mm, 14in-long, small drawer bottom, preserving thickness is particularly important, and you must also guard against the panel exploding as you apply clamp pressure. These panels are too thin for biscuits.
The solution is to use alignment blocks at the ends of the panel. These have cutouts to vault the glue-line squeeze out. They are clamped into place after glue and light clamp pressure are applied. If necessary,
I push (OK, and tap with a soft-face mallet, if necessary) the middle of the joint into alignment before applying modest final clamp pressure.
Biscuits are a fast, easy and practical way to align boards for glue-up
These easily made clamping blocks keep this thin panel aligned
Does it matter?
A problem with the two-at-once arrangement for thick boards is that a significant plane iron camber will be taking a thicker shaving corresponding to where the edges will meet, resulting in a panel that is not flat.
Consider an example. Assume a reasonable camber depth of 0.13mm over the full width of a 60mm-wide jointer plane blade. Pairing two 19mm boards will use 38mm of working blade width and a camber depth of .05mm over this width.
When two 150mm-wide boards are planed together in this way, then joined, the resulting panel with have a 0.4mm hollow across its 300mm width. With the convexity of the same amount on the other side, a total of 0.8mm of thickness of the panel will need to be removed, on this account alone, to make it flat. Wider boards, thicker boards, or more plane iron camber will increase the error.
Does this matter? Well, the error isn’t huge, but why use a process with an inherent error at all? One could set up the handplane with a straight blade edge to plane the paired boards, but the honing and use of this blade would leave no margin for error on thick stock. The danger is in creating a crown across the width of the edge, even the slightest of which can make for a poor joint. In summary, it is better to plane these thicker boards individually, and still have the option of using the self-correcting orientation for each alone.
