Woodworking with Plywood and Other Wood Cores
Plywood and other manufactured wood cores are fantastic raw materials to use in many woodworking projects. Plywood and wood cores come in a variety of styles and with a variety of veneers and finishes, all of which determine which type of wood core you'll want depending on your woodworking projects.
The inside of wood cores
Plywoods come with several different types of cores (the material between the outer layers), which are covered in the following sections.
Veneer-core has alternating layers of wood plies. This type of plywood is very common, but if you use it, be aware that your piece may have holes (called voids) in the inner layers that you can't see. Voids pose a problem when you cut the panel into smaller pieces, because you may cut into one and end up with a hole in the edge of the board.
Veneer-core plywood comes with a varying number of plies, from three up to eleven. For the most part, the number of plies relates to the thickness of the board (the more plies, the thicker the board). This isn't always the case, however. For example, you can buy plywood designed to be used for drawer sides; often called drawer-side plywood or Baltic birch. This type of plywood has more and thinner plies with fewer voids than regular veneer-core plywood. It's more expensive than regular veneer-core plywood, and you won't find it at your local home center — good hardwood suppliers will have it. But you may like it a lot better than using solid wood for drawer sides, and the plies look good enough to just finish with some oil or polyurethane.
Lumber-core plywood consists of narrow strips of wood that run parallel to one another. These strips are sandwiched between two outer layers which — like the veneer-core plywood — have their grains running perpendicular to one another. This makes for both a stable and strong core.
Home centers don't often carry lumber-core plywood, so you have to go to a good lumberyard to find it. It's worth a trip to the lumberyard if you want to build bookshelves or something that will carry a lot of weight, because lumber-core plywood is stronger than veneer-core plywood.
Medium density fiberboard (MDF)
MDF has no layer so it isn't technically a plywood — MDF is created from sawdust and resins — but woodworkers use MDF like plywood, and you will find it at the core of some of the hardwood veneer products.
Like plywood, MDF is very stable. But it's not very strong. It is very heavy, and it can be hard to work with. In spite of all this, cabinet makes often use MDF — but only where you won't see it once the cabinets are finished. If they do use MDF in an area where it is visible, it's always painted (it takes paints very easily). You can buy MDF from your local home center, either plain or with a veneer or laminate over one or both faces.
MDF produces a ton of dust when you cut or sand it, so wear a dust mask when working with it.
If you're deterred by the dust and mess that comes from using MDF, you might like flake board. Like MDF, flake board is constructed from small pieces of wood and resins and therefore it doesn't have the voids that may be present in regular plywood. Flake board is stronger than MDF because it's created by "flakes" of wood rather than sawdust, so the fibers are longer (which creates strength). It also produces a lot less dust. You can find flake board at a lumberyard or most home centers. Look for a product called OSB (oriented strand board).
The veneers on wood cores
Aside from having a variety of inner cores, plywood and sheet goods also come with a variety of outer skins (veneers). These include hardwoods and plastic laminates, which are the most popular styles.
But for the furniture-maker, hardwood-veneered plywoods are a dream come true. You get the benefits of plywood's stability but with veneer's economy. You can find many varieties of hardwood-veneered plywoods, including
These hardwood-veneered plywoods are great for building cabinets, shelves, and other woodworking projects that require a large piece of wood. The only disadvantage to using hardwood veneer plywoods is that you have to dress up the edges of the board because the hardwood veneer is only on the two faces of the board.