Hidden Compartment Bookshelf
Illustration by Mike Del RizzoWood Selection
The wood used in this project is sized so that all parts are readily available from any home centre or building supply store. In the case of the unit pictured here, the frame and fascia pieces are made from vertical grain Douglas fir. The top, middle and bottom shelf boxes are fir and mahogany plywood, and the center panels, shelves and back are made of pine. My supplier had some nice wide pine boards, which allowed the side panels to be made from one solid board. If you can't find wider boards, glue these up from narrower stock. The shelves are made from laminated pine shelf panels, and the back is frame and panel for rigidity, with the center panels being made up of ¼" solid tongue and groove pine paneling.
There are four main sections involved in the construction of this project – the sides, the back, the boxes, and the shelves. I used two different colours of stain on this project, and to make finishing easier and to keep any glue-related finishing problems at a minimum, I pre-finished all of the parts before assembly. To highlight the differences between the fir and the pine, I used Watco Natural Oil for the fir and Watco Cherry Oil for the pine.
The sides of the bookcase are constructed using frame and panel construction. The rails and stiles are vertical grain Douglas fir, and the panels are made of solid pine.
• Begin by selecting your lumber for the rails (D, E) and stiles (C). Try to choose clear, vertical grain stock. Dress it to a final thickness and width and then cut it to length.
• Build both sides at once, using the same machine set-ups to avoid alignment and assembly problems later. For strength, the rails and stiles are assembled using mortise and tenon joints; locate and cut these according to the plan. These can be cut quickly and accurately with a router and jig, or by hand with a drill and a sharp chisel.
• Use a table-mounted router and a carbide spiral bit to cut the grooves that hold the panels (A, B) in place. All of the panel grooves in this project are ⅜" deep and ¼" wide.
• Cut the solid pine panels (A, B) to size and using a table-mounted router, create the raised profile on the outer edges. I use a single-speed router, which doesn't allow me to use the large panel raising bits. I'm not particularly fond of the common profiles either, so I use a dish-carving bit for this task instead. It gives me a tighter looking profile, which I can safely mill, given the equipment that I have.
• Cut a ¾" x ¾" rabbet along the inside back edge of the two rear stiles (C). These will later receive the frame and panel back. The purpose of these is to soften the edges and provide a transition from the rails to the stiles that does not have to be sanded after assembly.
• Drill a hole at the bottom of each stile to receive a threaded insert. After assembly, install an adjustable foot to allow you to compensate for uneven floors.
To provide rigidity and resistance to racking (i.e. horizontal/vertical movement that would pull the cabinet out of square), the back is constructed using frame and panel construction. The frame and panels are both made from pine stock.
• To simplify material shopping, cut the frame member (T), and (U, V – not illustrated) from the same shelf stock that you will be making the shelves from. The stiles (T) will fit into the rabbets on the rear inside edges of the sides, while the location of the stiles will line up with, and be glued and screwed to the fixed shelves.
• Cut the mortises and tenons that hold the back frame assembly together, and mill the grooves to hold the tongue and groove pine panels.
• Cut enough tongue and groove pine boards to make up the two panels (W, X).
Hidden Compartment Boxes
There are three hidden compartments (boxes) - one under the top, one in the middle and the third at the base. The tops (R) of the middle and bottom box serve as shelves. The boxes are constructed out of plywood and fir, and then a trim board (Z, AA) is applied to the front of the boxes. The boxes are screwed from the inside to the sides of the bookcase. To keep the tops of the middle and bottom boxes from slipping off, rout a dado in the bottom of the tops (R) and install a corresponding 5⁄16" tongue in the top of the box fronts (J, M). The top (S) of the top most box is held in place with a piano hinge.
• Cut the bottom (F, I, L) of each of the boxes from a sheet of 1⁄2" plywood. For the middle shelf, be sure to orient the panel so that the best surface faces down, as this will be the visible surface after assembly.
• Cut the sides (H, K, N) and front (G, J, M) for the compartments as shown on the plans.
• Drill mountng holes in the side pieces for these compartments now, as it will be difficult to drill them properly after the compartments have been assembled.
• Assemble the box sections using glue and clamps.
Top secret compartment
Middle and lower compartments
There are 5 shelves - 3 of them are fixed (P) while the tops (R) of the middle and bottom secret compartments form the other 2 shelves. The shelves are made from laminated pine shelving material available at most building supply outlets.
• To increase the thickness of the fixed shelves (P) beyond the standard ¾", begin with 16" wide panels and rip them into three pieces, one at 12", and two at 1¾" wide.
• Glue the two narrow strips (Q) under the shelf along the front and back edge to build up the edge thickness to 1½".
• Cut the two hidden compartment tops (R) from the same laminated stock.
• Using the router with a chamfer bit, chamfer the top and bottom edges of the fronts of all of the shelves.
• Rout a groove along the center of the fixed shelves (P). This groove will receive the carved inlay (Y) and hide the glue line.
• Using a drill and a sharp chisel, or a router table with guide stops, cut the mortises for the shelf pins in the ends of the shelves. Recessing the shelf pins in this manner allows the hardware to be hidden as well as keeping the shelves captive. To remove them they have to be lifted up and out.
The shelf inlay (Y) is made of vertical grain fir in this case, but any hardwood would be a good substitute.
• Prepare blanks for the inlay using a jointer, table saw and thickness planer. The finished cross-sectional size before carving should be 5⁄16" x 5⁄16".
• The next step involves cutting the face into the small squares that will define the carving. Use a handsaw with a thin kerf and cut approximately halfway through the material. If you use a handsaw you will have to lay out each line on the strips. A much faster way is to use a band saw. Set up a block of wood to the side of the blade to limit how far you can cut into the wood. Place a line on the block of wood 5⁄16" away from the blade and line up the previous cut with this line as you go and you can accurately and quickly make these cuts with very little effort.
• Using a table-mounted router and guide blocks for safety, chamfer the two front edges of the trim to create a ⅛" wide face that runs the length of the three pieces.
• Use a sharp chisel to bevel the wood on either side of the saw cuts to form the points on the inlay strip.
• Use a sanding mop to quickly sand out any rough edges on the inlay strips.
The top (S) of the bookshelf is milled from a ¾" piece of MDF. This allows for a perfect cove joint at the front corners without having to worry about wood movement and cutting perfect mitres.
• Mill the cove edge into the front and sides of the MDF and sand the cove using the sanding mop.
• The bead moulding (BB, CC) that sits on the top (S) is milled from the same ¼" tongue and groove stock used in the back panels. Remove the factory-milled edge and use a ¼" beading bit to put a round profile on one edge of the ¼" thick stock.
• Mitre the beaded pieces so that they sit on top of the MDF and project approximately ⅜" beyond the MDF and use screws to fasten them in place.
Test fit all of the components, and when you are ready, lay them all out for finishing. All of the machining should be finished at this point with the exception of drilling the shelf pin holes, which is done after the sides are assembled.
• Sand all parts to 150 grit.
• Finish the fir using Watco Natural Oil.
• Finish the pine using Watco Cherry Oil.
• Paint the MDF cove as well as the carved inlay sections using milk paint.
This finish is ideal for these parts, as it will harden the MDF making it less susceptible to damage as well as giving the inlay a depth and complexity not possible with film-forming finishes.
• Assemble the sides first. Measure the diagonals to be sure they are square. Place the second side on top of the first to ensure that both are square and true to each other. The solid center panel should be free to expand and contract seasonally. Use clamps to keep them square until the glue has set.
• With the sides assembled, drill the shelf pin holes in each side. I use the Lee Valley 32mm jig, but a simple shop-made version would work as well. The key is to take the time and be as accurate as possible.
• Assemble the back panel, checking the diagonals for square once you clamp it. Let the glue set.
• Lay one of the sides on a bench and using a bit of glue and screws, attach the three hidden compartments using the previously drilled mounting holes. Attach the second side.
• Place the entire shelf, face down, on a worktable and fit the back using glue and screws in the rabbeted edge on the sides. Also, run a bead of glue along the back of the three hidden boxes and fasten the back to these using screws.
• Attach the three pieces of mitred cove to the MDF base, and attach the top to the bookcase using a piano hinge across the back. This forms the top of the upper hidden compartment.
• Fit the three fir fascia pieces (Z, AA) to the box sections to hide the box construction using clamps and glue.
• Install the two fixed shelf covers and the three movable shelves.
• Give everything a final coat of wax.
Heritage paints available at:Homestead House Paint Company Ltd