The Technique of FURNITURE MAKING

Dowelled joints

Spiral, grooved, and fluted or faceted dowel - pegs offer greater holding power than the standard smooth birch dowel-rod, and dowelled constructions are now used extensively in lieu of mortises and tenons. Providing the dowels are a good fit and enter not less that 1 1/4 in (32 mm) either side of the joint-line there is probably little difference in the ultimate strength. Figure 150:1 shows the standard birch dowel which should be saw-kerfed as shown to provide an escape route for trapped air and also for surplus glue; 150:2 shows the spiral grooved dowel and 150:3 the fluted dowel. Dowel-pegs can be chamfered or rounded with a dowel-rounder as in 150:4, and the seating countersunk at (B) to facilitate entry. A small gap should be left at (A, C) for trapped glue, and all dowels should be checked for diameter. If oversize they can be knocked through a dowel pop or plate (149) which can be purchased or simply made out of a piece of 1/4 in (6 mm) mild steel bar, accurately bored and countersunk on the underside. Some workers keep several dowel-bits in each size, for not only do the rods vary but also the critical diameter of the bits. Dowel-rod should be kept in a warm, dry place and purchased well in advance of use.

SETTING/LAYING OUT, ETC.

The usual diameter of dowels for normal work is 3/8 in (9.5 mm), with 1/4 in (6.0 mm) for thin stock and 1/4 in (12.5 mm) or more for stout frameworks. At least two dowels should be used to prevent swivelling of the joint, but if a light rail can only accommodate one, then a panel - pin should be driven through the framework from the back either side of the joint-line to grip the dowel. Spacing must be accurately done with a minimum of 3/16 in (5 mm) wood substance left either side of the dowel socket, and1/4 in (6 mm) between the bottom of the socket and the outer face, for subsequent shrinkage can shadow through if only a minimum of wood is left. Figure 150:5 shows the spacing for a normal rail 1% in (47.5 mm) by 3/4 in (19 mm) finish, and 150:6 staggered dowels in larger sections. Actual laying out is simple if the two members can be cramped/ clamped together in the vice (150:7), with a gauge-line run down the middle of the edge, working always from the face sides, and the positions squared across. Square sections many have to be marked out with a wooden template (150:8), or a dowel - jig of the Woden type (151); while an accurate hand-method is lightly to tap veneer pins truly vertical into the correct centres in one piece, nip off the pins leaving 1/8 in (3 mm) protruding, offer up the piece in the correct position and lightly tap the other end to register the imprint of the pin ends which can then be withdrawn and the sockets bored exactly on the pricked centres. Figure 152 shows the pins cut off ready for marking.