When it's time to refinish old cabinets, you may already know what you want. You may want a new color of stain or simply to pickle your cabinets rather than replacing them. Before you pull out the new varnish, get rid of your old finish. Old varnish can take a lot of elbow grease to remove, particularly if it's paired with a tung oil finish. Because tung oil can seep into the wood grain to a depth of up to 5mm, your best bet for removing it is to sand the topmost layer of wood off your cabinets.
Remove the varnish and strip away the wood layers that contain tung oil using 50-grit sandpaper and a finishing sander. Use even strokes that move with the grain of the wood. You should not have to remove more than 5mm of the surface layer of wood.
Wrap 50-grit sandpaper around a sanding block, and sand in crevices to remove varnish and tung oil in hard-to-reach areas.
Cover areas that you don't wish to sand with masking tape, particularly in areas where the wood meets, such as mitered corners. This prevents you from sanding against the wood grain.
Sand curved areas with 000 steel wool. If your wood has a veneer, the tung oil will not have soaked through the thin veneer. Use the 000 steel wool to remove varnish and tung oil without removing the thin veneer.
Clean surface with a soft-bristle brush.
Switch to a 220-grit sandpaper to smooth out rough spots on your wood surface.
Switch to 500-grit sandpaper and a vibrating sander to finish sanding.
Sweep surface with a soft-bristle brush, and rub the wood surface with a soft rag and paint thinner to remove dust particles.