How do you joint an eight-foot board?

Oak cabinet model
Oak cabinet model

Latest project is a display cabinet, and it’s a big display cabinet. Eight feet wide by six feet high by nineteen inches deep, made from solid oak with glass shelves and sliding glass doors.

Jointing, just to be clear, is getting the long edges straight and square so that when you glue them together there’s no gap. There’s a way of doing it on a planer, or on a router table, but that only really works if the table or fence is long enough to ensure that the board is at exactly the same orientation throughout the pass. Not an option with such a long board on my kit. Push it through the table saw? Same problem.

So it’s a case of putting the cutter to the board, rather than the board to the cutter.

First I tried using the hand router with a bearing guided bit against a straight edge. (You may notice I’m using old business cards as spacers on the second side.)

router jointing
router jointing

The trouble there is finding a  long enough straight edge; I thought the piece of ply I was using as a table was straight, but it turned out to be just a fraction of a millimetre concave. That was enough for a perceptible gap in the middle, which wouldn’t clamp shut, and in any case you want to minimise stresses in the wood.

Next I tried using the circular saw on a guide rail. I have two 1.4 metre guide rails which I can join in the middle. Trouble with this is that you have to set it up again for each board, and however tightly you screw the joining pieces on the rail, there is still some slop. Result: some of the joins are OK, but some aren’t. And I don’t have wood to waste; I want to take as little off as possible.

I tried using a hand plane, but not for long. Wonderfully satisfying in a spiritual sort of way, but still not accurate enough. I don’t have the ten thousand hours with a hand plane.

Finally, in the small hours, I hit upon a solution. The edge doesn’t have to be straight, in the Newtonian sense; it just has to fit the edge next to it. If you clamp both boards together under the guide rail and cut along both edges at the same time, they ought to fit exactly.

acclimatisingI shall try that soon. Currently the boards are sitting indoors, dry-assembled with biscuit joints and acclimatising, because I’m still not sure they aren’t going to move as they reach equilibrium with indoor humidity levels. I’m working on the short boards for the shelf dividers at the moment; they are small enough to be jointed on the router table.