Although adjustable shelves do not contribute to the strength of a bookcase, they do give it greater flexibility, allowing you to adapt to changing needs and organize space most efficiently. It is unwise to make a bookcase without providing at least one fixed shelf for structural rigidity.
Adjustable shelves are commonly held in place with wood, plastic, or metal shelf supports (page 43) that fit in holes drilled in the carcase sides. The trick is to make certain that the rows of holes are perfectly aligned. Use a commercial shelf-drilling jig (below) or a shop-made jig (page 46) to bore the
holes. Other options include adjustable shelf standards, which are mounted in grooves in the side panels, or shop-made corner strips (page 48). These are dadoed and attached to the interior corners of the bookcase to hold up the shelving.
Made of solid brass, these two-piece shelf supports add an elegant touch to a bookcase. The supports can be screwed into any of the threaded sleeves along the side panels, permitting the shelves to be mounted at any height in the bookcase.
This mounting system requires two parallel rows of holes to be drilled in the side panels of the bookcase. The commercial jig shown above allows you to bore holes at 1-inch intervals and ensures that corresponding holes will be perfectly aligned. Set the side panels inside-face-up on a work surface and clamp the jig to the edges of one panel; the holes can be any distance from the panel edges, but about 2 inches in would be best for the panels shown. Fit your electric drill with a bit the same diameter
as the sleeves and install a stop collar to mark the drilling depth equal to the sleeve length. Starting at either end of one of the jig’s rails, place the appropriate bushing in the first hole of the bushing carrier. (The bushing keeps the bit perfectly square to the workpiece.) Holding the drill and carrier, bore the hole. Bore a series of evenly spaced holes along both rails. Remove the jig and repeat for the other side panel, carefully positioning the jig so that the holes will be aligned with those in the first panel.
A shop-made shelf drilling jig
The T-shaped jig shown here will allow you to bore a row of evenly spaced holes as accurately as a commercial jig.
Make the jig from 1-by-3 stock, being careful to screw the fence and arm together at a perfect 90° angle. Mark a line down the center of the arm and bore holes at 2-inch intervals along it with the same bit you would use for threaded sleeves. To use the jig, clamp it to a side panel with the fence butted against either end of the panel and the marked centerline 2 inches in from its edge. Fit your drill bit with a stop collar, bore the holes, and reposition the jig for each new row.
1 Making and installing the shelf supports
Use a jig to bore holes for the shelf supports (page 45). Make two supports per shelf. Each one is a thin wood strip about 1 inch longer than the gap between the rows of holes; make the strip wide enough to hold a dowel at each end. (%-inch dowels are large enough for average loads.) To help you position the dowels on the supports, insert a dowel center into each of two parallel holes and press the strip against the points. Use the indentations from the centers as starting points for drilling the holes. Make the holes in the shelf supports the same depth as the holes in the side panels. Glue dowels into the shelf supports and, once the adhesive has dried, install them on the side panels at the height that you want the shelf to rest (left).
Preparing and installing the shelves
To conceal the shelf supports, cut blind rabbets in each shelf. Mark out the rabbets by positioning the shelf on the supports and outlining their locations on the underside of the shelf. Cut the rabbets using a router fitted with a rabbeting bit and square the ends with a chisel and a wooden mallet. The rabbets should be as deep as the thickness of the shelf supports. Once all the rabbets have been cut, test-fit the shelf in the bookcase (right). Use a chisel to adjust the rabbets, if necessary, to ensure a perfect fit that completely hides the supports.
Metal standards and clips are among the simplest accessories to install for mounting adjustable shelves in a bookcase. Two slotted standards, or tracks, are fastened to the inside faces of the side panels and shelf-support clips are inserted in the slots at the desired height. Rather than notching the shelves to accommodate the standards, recess the tracks in grooves cut in the side panels. Install a dado blade on your table saw and cut two parallel grooves in each panel. The grooves should be as wide and as deep as the standards; for the width of panel shown, position the grooves about 2 inches in from each edge. With the panels inside-face-up on a work surface, set the standards in the grooves and fix them in place, driving screws through the predrilled holes in the tracks (left)- Attach clips to the standards at each shelf location.
Making the corner strips
Dadoed corner strips installed in each inside corner allow bookcase shelves to be adjusted. You can make four strips from a single 4-inch-wide board that is long enough to extend from top to bottom of the interior. Install a dado head on your table saw and set the width equal to the thickness of the shelf supports you plan to use. Determine the desired spacing of the notches and cut two dadoes that distance apart in a miter gauge extension board. Line up the left-hand dado with the blade and screw the extension to your gauge. One dado should be offset to the right; cut a 2-inch piece of shelf support stock and press it into that dado, where it will serve as an indexing key. Butt one end of the workpiece against the key and cut your first dado. Cut the second and subsequent dadoes by moving the piece to the right and fitting the last dado over the key [right). When the dadoes are all cut, rip the board into four 1-inch corner strips.
Jig for routing evenly spaced dadoes
Attach the jig shown here to the base plate of your router to cut the dadoes in the corner strips of a shelf support system. (This technique can also be used to rout dadoes for fixed shelves.) Make the base from /Cinch plywood and the spacer from solid wood. Cut a bit clearance hole through the base and screw it to the router. Make the width of the spacer equal to the diameter of the straight bit you will use to cut the dadoes. Screw the spacer to the bottom of the jig base so the distance between it and the bit equals the spacing you want between the dadoes. Cut the first dado with the spacer riding along the end of the workpiece. Make subsequent cuts with the spacer in the just-cut dado.