Oak cabinet doors can be an impressive, natural-looking visual element in a kitchen, but they're only as good as their finish. If the stain and gloss on the doors has become worn and dingy, one option is to strip them down to bare wood and refinish them from scratch. The most effective approach is a combination of chemical stripper (to take off the existing gloss) and sanding (to take off the existing stain and expose the bare wood). This is a chemical-intensive project, so clear kids and pets from the area.
Remove the cabinet doors using a screwdriver. Take all hardware off the doors. Lay the doors on spread-out newspapers on your workbench or other surface.
Brush chemical stripper over the entire surface of each door. Let it work on the surface until the existing finish begins to ripple and bubble up, usually in less than five minutes.
Scrape off the softened finish with a plastic putty knife, pushing it forward in the direction of the grain. Get off as much of the finish as you can, applying more stripper if necessary.
Let the doors dry completely. Sand the surfaces with your vibrating detail sander and medium sandpaper, to take off any residual finish. Continue sanding until you're down to bare wood. Wipe off all the dust.
Brush on wood stain heavily with a paintbrush, letting it pool on the surface. Let it sit for a minute or so, then wipe up the excess liquid with old rags. If the surface isn't as dark as you want, repeat the process, letting the stain sit a little longer the second time around. Stain all the doors. Let them dry overnight.
Brush polyurethane over the doors in a thin, even layer, going with the grain of the wood. Let the polyurethane set for six to eight hours.
Lightly sand the polyurethane surface of the doors by hand, with fine sandpaper, just enough to dull the shine. Wipe off the dust. Brush on a second layer of polyurethane. Let it dry.
Hand-sand the second layer of polyurethane as before. Apply a third layer. Let it dry for 24 hours. Reinstall the doors.
Wear rubber gloves and goggles when using the stripper, stain and gloss. Ventilate the room by cracking a window.