MDF stands for medium density fiberboard, which is a sheet material manufactured from wood byproducts and adhesive, and used in cabinet construction. MDF is substantially less expensive than veneered plywood and is easy to work with. Its drawbacks are the amount of dust it creates when you cut it, and that it off-gases formaldehyde, which may irritate people with sensitive respiratory systems.
The cases for MDF cabinets are built by cutting the tops, bottoms and sides to size and screwing them together. MDF is subject to splitting during the screwing process if proper procedures are not followed. Drill a countersink and hole through the face of the piece you are putting the screw through, and a smaller pilot hole into the piece that the screw will be screwed into. You can also buy a special kind of screw called a confirmat screw, which is designed to go into MDF without splitting it. The joints of an MDF cabinet case can be further strengthened by running a bead of glue in the joints before assembling it.
MDF can be shaped, routered and notched in the same manner as wood. It is frequently used for painted raised panels in doors, although the frames are usually made out of wood. MDF is also suitable for flat panel doors. Making flat panel doors out of MDF is more practical and faster than making raised panel doors, since it is just a matter of cutting the piece of MDF to size and shaping it, rather than building a frame and assembling it around the MDF panel. MDF doors can be mounted with traditional hinges or hidden European hinges, and with any of the pulls or other hardware that are used with wood.
A subtle earth tone can be achieved by finishing MDF with a clear polyurethane. It won't show any grain, of course, but will appear similar to a dark paint. MDF in cabinetry is more commonly either painted or veneered with plastic laminate or with real wood veneer. Finishing with a durable finish or encasing the MDF in a solid veneer is advisable not only for aesthetic reasons, but also to minimise the off-gassing of formaldehyde that occurs with this product. Because MDF is a manufactured sheet product and has no grain, it does not grow and shrink with changes in humidity, and thus takes a paint finish well. Paint adheres well to its porous surface, leaving a smooth surface that is similar to a wall.