In the last Joinery 101 post, we took a look at joining boards using clamps and glue. Remove the clamps after two hours, if desired, but allow the glue to dry at least 24 hours before using the furniture. The technique consists of cutting the members to size and then drilling a series of holes in the joint surface of each member. Once you’re sure the pieces fit together correctly, apply glue to the end of the dowels and insert them in the holes on one board.
Get a scrap piece of plywood and try to drill some dowel holes in the edge and see if the ply splits. I’ll save you any suspense and tell you the two key factors for dowel joints working out well in the end are precise measurements and accurate hole-drilling skills. A crack inducer at the base of the concrete slab may be incorporated and a ‘starter’ joint created by sawing at a critical point during the curing process or insertion of a wet-former when the concrete is placed.
It needs little or no explanation beyond the fact that the dowels should be at right angles to the line of joint, and consequently the dowel at the outside edge of the frame will have to be much shorter than the others. There are also commercial systems available for screwed butt joints in which a plastic cap is provided with the screw to be fixed to the head of the screw after it has been driven home. A temporary filler strip may be positioned on top of the flexi-board to keep the joint free of concrete during placement. They are particularly convenient for panel glue ups as they facilitate alignment of panel members.
This is one of those joinery techniques where every trick-of-the-trade comes in handy; if you have any great tips for dowel joints, let us know. This type of joint is most commonly encountered on Pattern Imprinted Concrete paving, particularly residential driveways and patios. Test results show that dowels are the strongest method for creating this type of joint. Whenever we make a change in dowels, glue or our methods, we glue up some dummy panels for testing.
You can also cut a small kerf along the length of the dowel to provide a clear path for excess glue to escape. Saw each component to length and trim the ends of the rail square as described for making a square-ended butt joint (see page 18). I would not not use it for chair construction but have used it extensively in carcase construction particularly in unseen areas. Next apply glue to the mating faces and the exposed tips of the inserted dowels. Apply glue to the sockets in the joint’s other part and to the projecting dowel tips.
It helped me to imagine the two boards connected by a hinge so I could make sure I was marking the correct spots. If an old joint is loose but you can’t get it apart without damage to the surrounding wood, squirt a little hide glue behind the joint where it will do the most good. Loose mortise-and-tenon joints (left) are easy to fix; thicken them with wood shavings or shims. Wrapping the scraps prevents them from being accidentally bonded by squeezed-out glue.
For making an end to face dowel joint with the dowels hidden, the steps are similar except for drilling the holes. If you’re looking for a strong, inexpensive way to join two pieces of wood, don’t overlook the dowel joint. A dowel joint acts very much like a tenon (although not as strong) and must be a snug fit to be effective. Practice clamping the joint together without inserting the dowels or applying glue.
If it is desired to dowel irregular forms, or to make a number of joints just alike, this method will not give good results and save a great deal of time, but the pieces just alike will be interchangeable. The depth of the hole should be half of the length of the dowel (plus a little extra for glue); if you’re using a jig, you need to account for that as well. Dowel joints are therefore not a preferred joinery method for high-quality furniture.
Unless you can get a pocket hole jig big enough to handle coach bolts, I’d stay away from it. I also reckon pocket holes look cheap/tacky, but that’s another issue. Fibreboard or ‘compressible filler’ joints are usually quite scruffy looking, and the soft nature of the material, which allows it to absorb expansion and contraction of the adjacent slabs, also means it will abrade and deteriorate relatively quickly.
It is drilled from the outside face of the frame piece to be joined and therefore generally leaves an exposed dowel protruding after glue dries, and the excess dowell head is thus usually flush cut. Perfect dowel joinery happens only when the drill bit making the dowel holes is guided mechanically, which is why dowelling jigs were invented. If you’re joining 3⁄4″-thick x 21⁄2″-wide cabinet door frames, for instance, 5⁄16″- or 3⁄8″-diameter dowel pins that are 11⁄4″ to 11⁄2″ long are ideal. While you can do this manually, this is also where the dowel jig comes in handy.
Repeat by resetting the doweling jig and drilling all the remaining dowel holes into the numbered joint edges of the rest of the boards the same way. The #20 biscuits were a drop-in fit and glue was applied to both the slot and the biscuit. I mark the centre alignment of where I want the dowels on each board individually, and then use a square to mark the centre of each dowel on both boards. There’s a trick to making successful dowel joints: you need a jig that registers parts precisely.
This JessEm Dowelling Jig looks very good (well it would, wouldn’t it – it is their video!). Once this line has been drawn, using a set square mark lines across the grain of the wood (see second diagram). Step3: Now insert the dowel into one of the pieces of timber and insert the other piece on the other end of the dowel. Draw the pieces together by tightening the clamps until glue oozes from around most of the seams. To apply it, spread the loosened joint apart as much as possible without loosening other joints in the process.
Saw and plane the broken portion of the leg true as shown; take the timber which is to be jointed and treat it in a similar manner; now place four ordinary pins on the lower portion. The drill bit used should match the diameter of the dowel being used, thus ensuring a tight fit. To drill a dowel hole into the end grain of a workpiece, align a self-centering doweling jig index mark over your marked dowel location, top photo. If the joint is a little loose, glue will usually swell the dowels and tighten it up.
It certainly seems like creating a dowel joint should be easy, but it requires a lot of patience and attention to detail to do one correctly. Try compressing the dowels with a pair of the right shaped pliers to slightly decrease the size temporarily until the glue swells it tight. The intersection of the length and width lines show where the dowel holes will be drawn. If the mortise is worn and you don’t make a tight fit, the joint will fail, very quickly.