ost woodworkers make up the wide panels for a carcase by gluing boards together edge-to-edge. Building a carcase this way is not a matter of cutting costs at the expense of strength. Panels of edge-glued boards are every bit as strong as a single piece of lumber. In fact, a proper glue joint provides a sturdier bond than the fibers of a piece of wood.
Follow the steps detailed below and on the following pages to assemble panels. Apart from a supply of glue and an
assortment of clamps, all you need is a level work surface or a shop-built glue rack (page 24). To help keep the boards aligned, some woodworkers also use dowels (page 25). For more information on selecting glue, refer to the inside back cover of this book.
Selecting your wood is an important part of the process. Do not buy green wood or stock that is cupped or twisted, and avoid using wood with a high moisture content, which can adversely affect
the glue. Instead, buy lumber that has been dried in a kiln. If you are working from rough stock, begin preparing boards by jointing a face and an edge, then planing the other face. Next, crosscut the boards, leaving them roughly 1 inch longer than their finished length, and joint an edge of each piece. Rip the stock so that the combined width of all the boards exceeds the finished width of the panel by about 1 inch, then joint the cut edges.
Edge-glued boards should create the illusion of a single piece of wood rather than a composite. Experiment with the boards in different configurations to produce a pattern that is visually interesting, but make sure that the grain runs in the same direction on all of the pieces.
Arranging the boards
Set two bar clamps on a work surface and lay the boards on them. Use as many clamps as necessary to support the boards at 24- to 36-inch intervals. To keep the bars from moving, place them in notched wood blocks (inset). Use a pencil to mark the end grain orientation of each board as shown, then arrange the stock on the clamps to enhance their appearance (photo above). To minimize warping, arrange the pieces so that the end grain of adjacent boards runs in opposite directions. If the grain is difficult to read, dampen or sand the board ends to make it show up more definitely. Once you have a satisfactory arrangement, align the stock edge-to-edge and use a pencil or chalk to mark a triangle (right). This will help you correctly rearrange the boards if you move them prior to final assembly.
2 Applying the glue
To avoid marring the edges of the panel when you tighten the clamps, cut two pieces of scrap wood at least as long as the boards to be glued, and use them as pads. Leaving the first board face down, stand the other pieces on edge so that the triangle marks face away from you. Apply a thin glue bead to each board (left), just enough to cover the edge completely when the adhesive is spread. Too little glue will result in a weak bond; too much will cause a mess when you tighten the clamps. Use a small, stiff-bristled brush to spread the glue evenly on the board edges (above), leaving no bare spots. Do not use your fingers for spreading; adding dirt or grease to the glue will weaken the bond and slow the drying time. Move on to step 3 as soon as possible to prevent the glue from drying before you tighten the clamps.
Tightening the clamps
Set the boards face down and line up their ends, making sure that the sides of the triangle align. Tighten the clamps under the boards just enough to butt them together, checking again for alignment. Avoid overtightening the clamps or the boards may buckle up at the joints. Place a third clamp across the top of the boards, centering it between the two underneath. Finish tightening all of the clamps in turn (left) until there are no gaps between the boards and a thin bead of glue squeezes out of the joints.
Leveling the boards
For adjacent boards that do not lie perfectly level with each other, use a C clamp to hold them in alignment. Protecting the boards with wood pads, center the clamp on the joint near the end of the stock; place a strip of wax paper under each pad to prevent it from sticking to the boards. Then tighten the clamp until the boards are level (right). Refer to the manufacturer’s instructions for the glue’s drying time. If you are short of clamps, mark the time on the panel so that you can move on to the gluing of the next panel as soon as possible.
Removing the excess glue
Use a plastic putty knife to remove as much of the squeezed-out glue as possible before it dries. The moisture from glue left on the surface will be absorbed by the wood, causing swelling and slow drying; hardened adhesive can also clog sandpaper, dull planer knives and repel wood stain. Once the glue has dried, remove the clamps from the top of the boards, and use a paint scraper to remove any squeeze-out that remains (left)- Remove the lower clamps, then prepare the panel for joinery by planing it, jointing an edge and cutting the piece to its finished dimensions. Use a belt sander to smooth the surfaces that will be hard to reach once the carcase is assembled.
Preventing clamp stains
The metal bar of a clamp can be stained by adhesive that drips during gluing operations. Dried glue can also interfere with the ratcheting action of some clamps. To eliminate the problem, use a hacksaw or band saw to cut a roll of wax paper into 2-inchwide mini-rolls. Then, each time you apply a clamp, tear off a strip of paper to wrap over or under the bar.
A shop-built rack made from two sawhorses provides a convenient way to hold the clamps for gluing up a panel. To build the jig, remove the cross piece from your sawhorses. Cut replacements the same width and thickness as the originals, making them at least as long as the boards that you will be gluing.
Use a hand saw or a band saw to cut notches along one edge of each cross piece at б-inch intervals. Make the cuts wide enough to hold a bar clamp snugly and deep enough to hold the bar level with the top of the cross piece. You can also cut notches to accommodate pipe clamps, but bar clamps are stronger.
inches. The rest of the operation is identical to edge gluing boards on a work surface as shown in steps 3 to 5 on the preceding pages.
Many woodworkers use dowels to help with the alignment of boards in a panel. One of the problems in using this technique is that the wood pins have to be precisely centered on the edges of the boards to be joined. In the photo at left, location points have been made for the dowels—one about 3 inches from each end of the boards and one in the middle. A line is then scribed across the points with a cutting gauge set to one-half the thickness of the stock. The lines intersect at the center of the board edges, guaranteeing perfect placement of the dowels.
Boring the dowel holes
Locate points for dowels on the board edges (photo above). To avoid splitting boards with the pins, use grooved dowels that are no more than one-half as thick as the stock. Fit a drill with a bit the same diameter as the dowels, then wrap a strip of masking tape around the bit to mark the drilling depth, which should be slightly more than one-half the length of the dowels. Keep the drill perpendicular to the board edge as you bore each hole (right), withdrawing the bit when the masking tape touches the stock. (Although the drill press can also be used to bore the holes, keeping longer boards steady on the machine’s table may prove difficult.)
2 Pinpointing mating dowel holes
Insert a dowel center the same diameter as the dowels in each of the holes (above), then set the boards flat on the clamps with the triangle mark facing you. Align the ends of the boards and butt the edge of the second board against that of the first. The pointed ends of the dowel centers will punch impressions on the wood, providing starting points for the mating dowel holes. Bore these holes to the same depth as in step 1, then repeat the procedure for the third board.
Apply glue to the board the same way as when edge gluing (page 21). Then use a pencil tip to dab a small amount of adhesive in the bottom of each dowel hole. Avoid spreading glue directly on the dowels; they absorb moisture quickly and will swell, making them difficult to fit into their holes. Insert the dowels (above), then tap them into final position using a hammer. Avoid pounding on the dowels; this may cause a board to split. Close up the joint, then tighten the clamps (page 22). Remove the excess glue (page 23).
Inserting dowels with a depth gauge
To avoid the risk of splitting boards when inserting dowels, use this simple shop-made depth gauge. Rip a 9-inch – long board to a thickness that is exactly one-half the length of the dowels. Ъоге a hole that is slightly wider than the thickness of the dowels through the gauge near one end. Then place it around each dowel when you tap it into its hole. The dowel will be at the correct depth when it is flush with the top of the depth gauge.