Woodworker's Journal 2006-30-5, страница 19

methods that are believed to make a butt joint stronger, the most common being a spline. Splines are strips of solid wood, preferably the same material as the board, inserted into a groove cut along each joined edge. Now come the questions: How wide and deep should the groove be? What material should the spline be? How tightly should it fit the groove? The answers are overshadowed by two other considerations. First, cutting the spline grooves will remove a significant percentage of the area where the glue's specific adhesion can take place, thereby weakening the joint. Second, even if the interfaces of the joint are correctly made and it is tested to destruction, it will fail at the bottom of the groove where you have reduced the board's thickness.

Efficient, Reliable, Versatile

^rjp^This is a jubilee

year for Lamello. The tool was designed and developed in 1956 in Switzerland by Hermann Steiner. He was searching for a way to join a newly introduced material chipboard, now called particleboard. From an industrial point of view, he was beaten out by the 32mm point-to-point boring system, but his design still earned praise from the New York Museum of Modern Art as one of the most useful inventions of the 20th century. Plate joinery is now used worldwide in shops large and small as an extremely efficient, reliable and versatile joining system.

In light of these two points, if you still believe that a spline truly helps, keep it thin: a 1/8" saw kerf is enough. Make the spline a snug push fit and its width about three times its thickness in each board.

Another option is to use joining plates, more familiarly known as biscuits these days, which improve upon the spline method in several ways. For one, the groove is inter

mittent rather than continuous, which preserves more area for the glue's specific adhesion to occur. Second, the biscuits are made of European beech, a particularly strong wood. Third, because the grain of the biscuit runs on the bias, it is angled across the joint line, resulting in greater strength. Fourth, the biscuit is compressed at the same time it is stamped out: a biscuit snugly fits in its 4mm kerf when dry, but when wetted by the glue, it swells, causing internal pressure and a strong resistance to being pulled apart.

Preparing to Glue

Once you've satisfactorily planed the edges, you can glue and clamp the joint together. Begin by assembling the clamps, arranging the

Gluing Up Witk Biscuits

Deposit glue in the slots, wet the slot sides with a paddle and remove excess glue. Then roll glue on the two edges to coat the mating surfaces.

Wet the biscuits with a paddle and insert them in the slots.

Woodworker's Journal October 2006 19

Assemble the two boards, aligning them with the chevron mark that recorded the composition. Repeat the procedure to include the third board, if applicable.

Position the clamps alternately above and below the assembly. This will counteract the tendency for the boards to buckle as you apply pressure.