You don't have to get far into the construction process to appreciate the simplicity of making a biscuit-joined door. We rip the frame members to width, chop-saw them to length, then proceed to lay out the joinery. There are no mortises or tenons to cut; nor is there any work to be done on the shaper. A single layout line across each joint is all you need to align the biscuit joiner. Wc like to arrange the entire frame assembly on the workbench, and mark all the joints at once.
As shown in the inset photo on the opposite page, the thickness of the door allows for a "stack" of three biscuits to be used, each one spaced '/2 in. from its neighbor. S-6 biscuits require deeper, longer slots than standard biscuits. If your joiner has an "M" setting, this will give you the proper cut. Otherwise, adjust your machine to make a V8-in.-deep slot. To elongate the slot, wc cut */8 in. to the right and left of the layout line.
We cut the bottom slot first, with the biscuit joiner and the frame members flat on the benchtop. Then we add a l/2-in.-thick spacer to make the middle cut, and another V"2-in. spacer to cut the top slot. With this technique, you get three accurate slots from one layout line. (See top photo, page 66.)
We prefer to use urethane glue (either Gorilla Glue or Excel) for assembling the door frame. This type of glue is strong and completely waterproof. Also, the adhesive expands slightly as it cures, taking up any play between the biscuits and their slots.
Polyurethane glue relies on moisture to cure. We've found that by moistening joints just before applying glue, we can improve joint strength by up to 30 pcrcent. A couple of "spritzes" with a plant mister is all you need—just enough moisture to darken the wood slightly.
After moistening the joint, we brush glue thoroughly into each slot, also taking care to lightly coat mating sections of edge grain and end grain. Even though end-grain adhesion won't contribute much to the strength of the joint, the glue effectively seals the porous ends of the rails and dividers.
We start the frame assembly by gluing the upper and lower dividers to the middle rail. The same cross-joint marks used to align the biscuit joiner can now be used to align these joints. The top and bottom rails go on next; the stiles are glued on last. Moderate clamp pressure pulls it all together. (See center photo, page 66.)_
In this door design, the panels aren't held by grooves in the frame members. Instead, several layers of panel material arc sandwiched between moldings that wc apply from the interior and exterior sides of the door. With this technique, the only machining on the frame members is the small rabbets that wc rout around the inside of each panel opening to receive the interior panel material. (See Fig. 2.)
Wc mill the rabbets with a standard rabbeting bit and square up the corners with a bench chisel. (See bottom photo, page 66.) Then we cut the t/8-in.-thick plywood panels to fit in the rabbeted openings. These panels will cover the foam insulation and act as backer boards for the twigs. Don't install the panels yet; you'll need them to lay out the exterior panels, as we'll explain below.
Now for the trim. The exterior trim is a simple molding made from V8-in.-thick pine. It has an "L" profile, with hand-planed chamfers on the two outside edges. (Sec Fig. 2.) The interior molding is also pine, and measures Vl in. by 1 '/4 in. in section. Both of these profiles are easy to make and inexpensive; they're also consistent with the Spanish Colonial style of the finished door. For a different style door, you might opt for trim with a more elaborate shape. It's easy to make your own on the router tabic, or to modify a standard lumberyard molding.
We install che exterior trim first, mitcring the four pieces that fit around each frame opening. (See top photo, opposite page.) We use urethane glue and 1 '/4-in. brads to secure the trim to the frame. When all the exterior trim is on, placc the door on the workbench with the interior side facing up.
For the exterior panels, we've used quite a few different materials to suit a client's tastes or to fit a particular decor. It's possible to have a flat panel or raised panel made from solid wood. Or you can use tongue-and-groove (T&G) boards as we do on this door. By choosing a thinner exterior panel—*V8-in.-thick T&G boards, for example—you make room for more insulation or a thicker interior panel. Since the panels are installed after the door frame is together, your options are numerous—another reason why wc like this type of door.
The nominal 1x4 (-V4 x 3'/2) T&G board wc use to panel this door is known at many lumber yards as "headboard," or beaded ceiling paneling. Wc call it "car siding" after the historic style used on wooden railroad cars. We install the boards on a 45° angle, creating diagonal joint lines that break up the horizontal and vertical lines of the frame while also enhancing its symmetry. We like the visual interest this creates, but here again, you can install your panels to suit your own taste.
With diagonal paneling, note that the panels on both sides of the dividers need to have their joints running in opposite directions. Also, you'll want to lay out your T&G boards so you don't end up with a tiny corner piccc that doesn't look good or fit well. To solve this problem, wc work out the layout of the boards on the '/8-in.-thick plywood panels cut earlier. Measure '/2 in. in from the edge of an upper or lower plywood panel, and you'll get the actual dimensions of the panel opening.
Mark up the plywood with 45° diagonal lines, spaced 3'/4 in. apart (the width of our boards minus the V4-in. width of the tongue). This will give you a good idea of how to placc the boards. Wc mark the boards using che perimeter line on the plywood panel, make the 45° end cuts on the chop saw, and then simply dry fit the T&G panel into the opening.
Foam, Plywood and Twigs
Next, we lay a bead of panel adhesive down the middle of each board and press in a '/2-in.-thick sheet of foil-faced foam insulation, cutting each piccc for a tight fit in its opening.
FIG. 2: PANEL INSTALLATION DETAILS
Quick rabbet. Chuck Ring rablx>ts the frame on the interior side of the door. The rablyet will hold a thin plywood panel and the twigs that show on the interior of the finished door.
Slot machine. Hanson mills the topmost biscuit slot in a door stile, using two 1/2-in.-thick spacers beneath the joiner to keep the slots parallel and evenly spaced.
Framed up. The authors clamp up the door, using a pair of tape measures to check for square by comparing diagonal measurements.
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