There are notable advantages associated with dowel joints. Adhesive based butt and mitre dowel joints are routinely used to produce invisible joints and to reduce assembly costs in the furniture industry. However, when using common loose grained particle board, long-reach drills and special dowels must be used. Using a dowelling jig and dowel centres makes producing dowel joints fairly easy. This makes them a popular choice among professional and DIY cabinet makers.
To join two pieces of wood, drill two opposing holes in both mating surfaces, half the length of the dowel. Apply glue to the joint faces and inside the holes. Insert precut dowels into the holes on one of the pieces. Bring the two haves together and insert the dowels into the matching holes on the second piece. Clamp the joint, wipe off the excess glue with a damp rag and you're finished.
The most difficult part of making a dowel joint is drilling the holes accurately. However, using dowel centres or a dowelling jig simplifies this process. A dowel centre is a round metal plug with a flange on one end to hold it against the surface of the wood, and there is a sharp point protruding from the centre of the flange. To use dowel centres, drill one set of holes at right angles into the face of the first piece of wood. Insert the correct size dowel centres into the holes and bring the two halves of the joint together with moderate pressure. The sharp points on the dowel centres will mark the mating holes on the second piece of wood. Drill these holes and complete the joint as described above. Dowelling jigs are fitted with drill guides and clamps that allow correct positioning and precise drilling. Consequently, with the help of a dowelling jig, a perfect dowel joint can be accomplished in minutes.
With dowel joints, there are no unsightly dovetails, fasteners or brackets marring the appearance of fine pieces of furniture. The dowels are buried in the wood, with only a thin glue joint visible on chair legs, table legs and the sides of cabinets.
There are two types of stress imposed on dowel joints, sideways or “shear” stress and withdrawal stress. Dowels are usually made of yellow birch, beech or sugar maple. These woods have long, tough fibres that allow them to withstand heavy shearing loads. As for withdrawal stress, once cured, modern polyvinyl acetate (PVA) adhesives used on dowel joints make it almost impossible to pull the joint apart.
Correctly positioned dowels allow two halves of a joint to be precisely aligned without using special jigs or equipment. Consequently, tooling costs are kept to a minimum because no expensive machining, other than use of a simple twist drill, is required. Finally, dowel joints can be completed in minutes, which reduces labour costs.