In many parts of the woodworking community, it is almost sacrilegious to promote finger joints/box joints in lieu of dovetail joints. The dovetail joint has a long history in woodworking and is still viewed as the signature joint of a fine craftsman. The joint was valued because it provided a form of mechanical lock when glue failed. With today's much stronger and more durable glues, the joint has become more decorative than functional. In fact, the most elegant joints with the slimmest pins are the weakest of the dovetail joints, substantially weaker than alternative joints.

With box joints, you can easily get greater surface area for gluing and the joint will have much greater racking strength than a dovetail joint. In simple tests we performed, there was a fairly direct relationship between joint gluing area and strength. This is what you would expect and is the reason that so much trim today is made from finger-jointed stock with very fine fingers. In addition, the fingers are tapered, not only to make it easier to assemble the joint, but to minimize the weakest part of it, the tip, which has the same strength as a butt joint.

There is a new and interesting development in this field. A number of years ago, one of our customers (a commercial box maker) told us he was assembling his boxes before gluing the corners. With the use of a low-viscosity glue, he was able to paint the corners with glue, which would then have a tendency to wick into the joints. Equally important, it wicked directly into the end grain of the wood, causing it to swell, which created a mechanical lock that would let him tap his boxes into perfect squareness and be confident that they would remain that way since they locked up quite quickly. What he had done was create a combination dovetail joint/box joint since the tips of all the fingers were somewhat thicker than their bases. After curing, he sanded the box on all sides to remove surface glue.

Since we developed Chair Doctor™ (#05K99.01) glue with low viscosity and low surface tension, this whole process has become much more effective. It is particularly effective on softwoods where you get a mechanical lock almost instantly when you apply the glue, but it is also effective on hardwoods because the much slower penetration of the end grain allows for longer wicking time between the finger surfaces.

For most small boxes, there is more than adequate strength in this type of joint. In commercial production, it is a godsend to be able to glue after assembly.

Incidentally, when the customer told us many years ago of this process, he asked us to keep it confidential because it was one of his competitive advantages. We have kept it confidential these many years but, recently, several users of Chair Doctor™ glue have told us that they are using this system and had developed it independently based on the wicking features of Chair Doctor™ glue. It seemed to us that this freed us from our earlier vow of silence.

– L.L.