It may be a budget building material, but medium-density fiberboard (MDF) has two advantages over wood and plywood that make it a good choice for cabinet doors. One is that it resists warping, and the other is that it has no visible grain, so you can get a smooth finish. You can shape it or trim it to create a variety of styles using the same tools you use for any woodworking project.
Cutting the Doors
You can cut MDF with a table saw or circular saw but to avoid lugging around full sheets, which can weigh as much as 100 pounds, you may want to have them partitioned into smaller pieces at the lumberyard. When you cut the doors to their final size at home, measure and cut from the back to minimize chip-out along the front edges. This means pushing sheets through the table saw face-up. Be prepared for an extreme amount of dust; wear goggles and a dust mask while cutting. Make sure your saw has a sharp blade to avoid burnt edges.
Trim or Rout for Style
One way to add style to the doors is to glue or nail wood molding to the front. The molding may be as simple as flat boards that raise the edges around the perimeter and create a recessed center, or it may be shaped to provide more of a picture-frame effect. After mitering the ends of the trim with a miter saw, glue them with a thin coat of construction adhesive and secure them with a brad nailer. If you prefer, forgo the trim and shape the edges with a router for a smoother, minimal design.
Painting the Doors
When painting MDF, it's fairly easy to get the surface smooth, but the edges are another matter; it typically takes two coats of primer to properly seal them. The best primer to use is a solvent-based one because water-based primer causes the material to form small blisters. You can brush on the primer and the paint, but if you want to get the smoothest finish, it's best to spray. After priming both sides of the door and the edges, sand the door and edges with 220-grit sandpaper, then prime and sand the edges again. The door now is ready for two coats of finish.
After positioning the doors and marking the positions of the hinges, it's important to drill pilot holes for the hinge screws before driving them. A 1/8-inch drill bit works for most cabinet screws. MDF cabinet doors look best with hidden hinges; these require you to drill large holes on the back of the door. If you are making doors for a set of cabinets, it may be worth it to buy a special jig for drilling these holes. If you're just making one or two doors, you can make the holes with a Forstner bit and the template that comes with the hinges.