Questions concerning medium-density fiberboard? Find out your answers here.
Story 362

Many of the projects in your magazine call for medium-density fiberboard, but I've been unable to find it. I'm curious as to what it is, how and when I should use it, and how I get it.
-Duane Pulliam, Chatham, Ill.

Medium-density fiberboard, or MDF, has become one of the most popular composite materials in recent years, Duane. Because MDF is uniform, dense, smooth, and free of knots and grain patterns, it makes an excellent substitute for solid wood in many applications, except when the stiffness of solid wood is required, such as in a long bookshelf. Its smooth surfaces also make MDF an excellent base for veneers and laminates.

We use MDF anytime its heavy weight isn't an issue, and when we don't want wood grain showing, such as in painted projects. We used it to make the fireplace surround from issue 101, shown above.

Much like particleboard, MDF is made up of wood particles and resin. But these particles, which are cooked and pressure steamed, also get separated uniformly to make a fine, consistent material. Then the manufacturer binds the wood particles with an adhesive and heat presses the composite.

Because of MDF's consistent make-up, machining this material with the right tools results in clean, sharp edges without chip-out or fuzzing. Because MDF is more dense than most woods, manufacturers recommend only the highest quality tools be used to machine it. Most toolmakers have specifically designed carbide, ceramic, or diamond tools for cutting MDF. Due to airborne wood particles and resin, be sure to use a dust mask and dust collection system when sanding and machining.

Tips for joining MDF include using yellow woodworker's glue and untapered sheet-metal screws or production screws instead of wood screws. MDF panels hold screws as well as most natural woods, but drill a pilot hole first. You also can join this wood composite with spiral grooved dowels, coated staples, and ring shank nails.

Athough most home centers now carry MDF, it is often called by other names, such as Medite or furniture-board. It typically costs $17-$20 for a 34 " x 4' x 8' sheet.