Building bookshelves can be a common woodworking project whether they are freestanding or built-in wall unit. When you are building a bookshelf you will need to support a considerable amount of weight such as books or even electronic equipment. A single three-quarter inch thick piece of plywood may sag in the middle under the weight of a heavy item placed on the shelf.
Therefore you know that shelves need to support considerable weight perhaps even a couple hundred pounds so here are some woodworking ideas for superstrong shelves you should remember:
One idea is to employ an edge similar to a breadboard edge. This type of edge can be applied to dimensional woodstock or along the edges of a thick piece of plywood to cover the unsightly edges of the plywood. This breadboard edge is a tongue and groove joint with the tongue is cut on a piece of hardwood that will fit into a groove in the edge of the shelf plywood. The plywood is wrapped on all four sides with his tongue and groove hardwood edging, and using 45° mitered corner joints. The tongue provides a considerable amount of strength to a shelf even though it can be time-consuming.
Keep in mind that should you intend to stain the shelves, the hardwood you choose stains to a different color than the plywood, so make it a design feature and accentuate the differences.
Another idea that is more expensive but a simpler way is to sandwich two layers three-quarter inch plywood to make a 1 1/2 inch thick shelf.
This idea should be avoided if you are choosing a hardwood for dimensional lumber as the expansion and contraction can cause undue stress on the glue joint between the two layers. If you plan to use hardwood or dimensional lumber it's easy to obtain 1 1/2 inch thick dimensional lumber for to plane down a much thicker piece of hardwood.
This technique of sandwiching two pieces of stock with glue is ideal if you intend to use two layers of plywood. Simply apply a thin, and even coat of quality woodworking glue to the surface and pressed together, hold the sandwich layers with clamps until the glue dries.
Once the glue is dried remove the clamp scrape off any excess glue and trim the exposed face with a piece of 1 x 2 in the wood of your choice. Begin with two pieces of plywood that are slightly larger than the finished size, in case the two boards are slightly offset after the glue dries. In such a case, the sandwich plywood shelf can easily be trimmed on all four sides to get the desired finish size of the plywood shelf. The 1X2 board can be attached to the edges of the shelf using biscuit joinery for finish nails.