Cajón means crate or drawer in Spanish -- this aptly describes the appearance of a cajón drum box. Made of plywood, the cajón is usually 45 to 50 cm (18 to 20 inches) tall. The drum is played with brushes, a bass drum kick-pedal or the hands, but never with wooden sticks, and is struck near the edge or in the centre. Some cajóns have snares or guitar wires installed just behind the tapa (the striking face or drum head), which adds a metallic sharpness to the tone.
A cajón drum box is made of plywood, which, because it is made of layers of wood, is strong, even at thinner widths. Use 3 mm (1/8 inch) thick plywood for the tapa, 1.2 to 1.8 cm (1/2 to 3/4 inch) thick for the cabinet. Hardwood plywood produces the best sound. Various woods are traditionally favoured, and produce slightly different sounds. Beech produces a dry, rich sound with centre strikes, and a clear, crisp sound when the tapa is struck near the edges. Burlwood produces a richer sound overall, while zebrawood cajóns have a rich bass sound and added warmth with edge strikes.
Use a fresh bottle of wood glue for this project: Buy it from a store that buys large quantities and likely turns it over quickly to ensure the freshest product, as this will achieve the best results. Most of the joints will be glue-only joints, so excellent-quality, fresh glue is very important.
If you want to add the metal-string sharpness to your cajón, use either metal guitar strings (the G string is a good choice) or install a snare drum replacement wire. You can buy both from any music store that stocks school band instruments, or they'll be able to order them for you if they don't have them in stock. The snare wire will cost around £6, the guitar strings under £3 each. You'll also need small tacks or finishing nails to affix these to the cabinet frame.
You'll need wood screws to affix the tapa to the cabinet: four for across the top, and one each for the right back and left back.
If desired, purchase wood stain to enhance the wood grain; you'll need to sand, finish and seal the drum box to protect it from warping and to make sure the drummer doesn't get wood slivers from hitting or sitting on the drum cabinet. Varnish, polyurethane or a hand-rubbed tung oil finish will work.
Finally, you'll need four 5 to 7.5 cm (2 to 3 inch) high ready-made cabinet feet for the bottom of the cajón.
Standard hand and power tools from a modestly-equipped wood shop will suffice for this project. Essential tools include a sabre saw to cut the resonance hole in the back of the cabinet and a power drill fit with a grinder to finish the resonance hole, plus a circular saw or other saw that will cut accurate straight cuts. A palm sander will make quick work of the sanding chores, although it isn't necessary. You'll also need a screwdriver and a hammer, and a wood rasp.
Design and construction tips
The cajón is a rectangular box, usually 50 cm (20 inches) tall. The width varies, but is usually 30 to 32.5 cm (12 to 13 inches), and the box depth (front to back of the drum) is generally the same length as the width. Cut the sides long enough to allow a glued overlap for the joint with the back piece. The top and bottom pieces are usually square, and are glued to the top and bottom of the rectangular box.
Cut a circular resonance hole, about 1/3 the width of the back, into the center back piece of the cajón box. Use a jigsaw to cut a rough opening slightly smaller than the completed hole, then use a power drill fitted with a grinding bit to grind out the remaining wood material until you have an attractive circle. Bevel the inside edges of the hole.
Assemble the bottom, back, sides and top into a rectangular cabinet, glue and clamp them in place, and allow the glue to dry before you install the tapa. Butt joints will be stronger glued joints, so use them instead of mitred joints.
If you want to install guitar strings or drum wires, glue a frame of 2.5 by 2.5 cm (1 inch by 1 inch) wood lengths cut to fit to the inside front of the cabinet, flush with the Inside rim of the cabinet front. When the glue dries, nail the strings or wires to the outside face of the frame, nailing them in place so that they are tautly strung between the top and bottom frame.
Cut the tapa from the 3 mm (1/8 inch) thick plywood. It should measure the exact width of the cabinet front in width, and should be an inch longer than the cabinet front. Then, position the tapa piece over the top of the strings or wire, sandwiching them between the frame and the tapa. The top of the tapa should be even with the top of the cabinet, and the bottom end should extend an inch below the bottom of the cabinet. Secure the tapa to the cabinet (not the frame) using wood screws: four evenly spaced across the top of the tapa, and one each securing the tapa to the right and left cabinet front, about halfway down the length of the tapa. Do not nail the bottom half of the tapa to the cabinet.
Sand the cajón exterior with gradually finer-grit sand paper until the finish is smooth and free of slivers, stain if desired and finish with the wood finish of your choice.