How To Patch a Small Metal Hole
Preparing the Hole
Use coarse sandpaper to remove paint, rust, oil and dirt from the surrounding metal in a minimum 1-inch wide border around the hole on both sides of the metal. Leave the surface rough but clean. On the back side of the metal, use a putty knife or the applicator supplied with the kit to coat the border with epoxy filler. Then use a putty knife to press into the epoxy the edges of a piece of fiberglass screening cut 1 inch larger than the hole. Let the epoxy cure, following the maker’s instructions.
Filling the Hole
Working from the front side and using the kit applicator, a putty knife, or even a stiff piece of cardboard, cover the screening with epoxy. Apply epoxy until the hole is filled. Then build up the epoxy above the surface of the metal and let it slightly overlap the edges of the hole. Allow the epoxy to cure.
Sanding the Patch
Use rough (about 40-grit) silicon-carbide sandpaper to reduce the built-up dry epoxy to the level of the surrounding metal; a power sander will speed the job. Then use 80-grit sandpaper followed by 200-grit or 300-grit to make the patch glass-smooth.
Coating the Patch
To remove dust and grit, wipe the patch with a soft cloth soaked in rubbing alcohol. Spray the patch with primer, holding the can approximately 6 inches from the surface of the metal and moving it slowly from side to side in a straight line, not in an arc.
Sand the primer surface with 300-grit wet-and-dry silicon-carbide sandpaper dipped in water. Then wipe the surface again with an alcohol-dipped cloth, and spray on a finishing coat of paint. When the paint has dried, sand the surface again, clean it, and apply a second coat of finishing paint. Once this coat dries, buff the surface with a soft, clean cloth.