Rob Porcaro's Edge Joint Techniques
Woodworker Rob Porcaro details his hand-planing methods for creating perfect edge-to-edge joints, emphasizing accuracy, tool selection, and glue-up
Rob Porcaro shares his shop-proven techniques for accurate edge jointing and glue-up alignment. The fundamental simplicity of the edge joint demands precision, as even tiny gaps are visually and structurally unacceptable with the finished joint fully exposed.
A Perfect Joining Edge
The joint edge of a board should have a slight camber, or concavity, along its length. There must never be the slightest convexity across its width. When the camber is closed with mild pressure, the edges should fully mate along their entire length to produce a flat panel. Hand planing creates an ideal surface for gluing. A small-shop woodworker can use a well-tuned jointer or tablesaw to bring the edge close to ready, but a hand plane should be used at the end for perfect mating surfaces. The same results can be achieved from a hand-ripped edge, though it takes longer.
The Tools at Hand
An essential tool for all but small work is a long plane. These are superb for bridging valleys and levelling hills to produce an accurate edge. Porcaro prefers his #7 jointer plane, which is 22in long with a 23⁄8in-wide blade. Some prefer the beefier #8 plane at 24in long with a 25⁄8in blade. For long grain shooting of boards up to about 600mm, he likes his boxy, heavy 11in #9 shooting plane, but a regular bench plane will also work.
| Plane Type | Length | Blade Width |
|---|---|---|
| #7 Jointer | 22in | 23⁄8in |
| #8 Jointer | 24in | 25⁄8in |
| #9 Shooting | 11in | - |
The Importance of a Sharp Plane
It is difficult to overstate the importance of sharpness in producing accuracy. The edge of a dull blade gets excessively deflected into the wood, reducing control of shaving thickness. A sharp blade can take thinner shavings with less blade deflection and less pushing effort. This makes the planer easier to control and produces a more consistent edge.
Planing Without a Jig
This time-honoured technique is called the camber shift method. Set up the plane by centring the depth of the blade camber across the width of the sole. The camber amount is closer to that of a smoothing plane than a jack plane. Make corrections to an out-of-square edge by shifting the plane laterally to let the camber depth take down the high side. You shift, not tilt, the plane. Secure the board vertically with its edge only an inch or two above the bench surface to help judge if the plane sole is parallel with the bench top. With practice, it is fairly easy to correct an edge consistently out of square along its full length.
Easy Hand Planing
This method has worked for Porcaro for over 30 years. He has tapped three 10-24 threaded holes in the side of his Lie-Nielsen #7 to accept a simple, two-part wooden fence that runs the plane sole square to the side of the board. The inner part of his fence, which contacts the side of the board, is 280 x 45mm. Commercial models are now available. The blade is slightly cambered to prevent any convexity across the joint edge width. You can save a trip to the sharpening bench by swapping out the inner part of the fence with one of a different thickness.
**Planing a Thin Piece of Wood**
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 to 750mm long. The solution is to lay these boards flat and shoot the edge with the plane on its side. Porcaro usually uses his long shooting board for this. The end stop helps stabilise the workpiece, and the plane rides on a slick plastic surface. For shorter pieces, he likes to use a grippy glove on his left hand, but longer pieces should be stabilised with clamps.
**Planing Two Pieces at Once**
It is sometimes suggested to plane two edges at once in a closed bookmatch orientation as a quick 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. However, with thicker boards, say 19mm, and using a jointer plane prepared with a typical camber, an inherent error in the process becomes significant.
**Assess Your Edge**
You can save trouble by evaluating the initial edge condition with a straightedge and square. To produce the joint camber, start by taking a thin shaving or two from the middle of the board's length. 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 no localised bumps or troughs. On longer boards, it is easy to overdo the camber.
**How to Attach Two Boards Together**
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. Porcaro does not use cauls, complicated over-under clamps, pinch dogs, dowels, Dominos or splines. For 19mm stock, he uses #20 or #10 biscuits, and #0 for 13mm stock, typically 200 to 300mm apart, and about 50mm in from the ends. The biscuit joiner's fence must be set accurately square to the blade slot face.
