It can be challenging to fix broken particleboard because it isn't the densest or most stable of building materials, which is why it's one of the least expensive. It consists of wood chips compressed with resin into plywood-size 4 x 8 sheets, and it's often covered with a wood or plastic veneer for use as a cabinet material. When you use it for cabinets, you usually have to use screws, and it's common for the screws to loosen and fall out as the material around them chips out.
Holes around chipped-out screws can be repaired in more than one way, but options are more limited if you have to repair a large hole that happened because of an impact or moisture damage. Fortunately, there is an effective way to fix broken particleboard with large holes, but hiding the repair is difficult unless you're prepared to paint afterward.
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Fixing Screw Holes With Epoxy
A common scenario is when a cabinet door pulls away from a cabinet made of particleboard, leaving one or more holes incapable of holding screws for the hinges. One way to fix this problem is to fill the holes with two-part epoxy wood filler or glue.
Mix together the two parts of the product you purchased according to the instructions on the container and then spread the mixture liberally inside the hole. Scrape away the excess material before it sets, which could be as soon as five minutes depending on the product, so don't be slow. Wait for an hour longer than the cure time specified on the product label (just to be sure) and then drill a pilot hole in the epoxy for a new screw or drive the screw directly into it.
Fixing Holes With Dowels
An epoxy repair is strong, but it doesn't look very good. If you need a better-looking repair for a cabinet or piece of furniture, you can fill holes with wood dowels. Start by buying dowel material that is considerably larger in diameter than the hole you need to repair. For a typical screw hole, a 1/2-inch dowel might work, but you may have to upsize to 5/8 or 3/4 inch.
Choose a drill bit with the same diameter as the dowel and drill a pilot hole centered on the screw hole you need to repair. Wrap tape around the bit to mark the depth of the hole; it shouldn't be any more than 3/4 of the thickness of the material. After drilling the hole, clean it out, squirt in some carpenter's glue, and then tap in the dowel. When the glue sets, cut the dowel flush to the surface of the particleboard with a hand saw, sand it down, and it's ready for a new screw.
How to Fix a Large Hole
The only realistic way to fix a large hole in particleboard is to use a technique similar to the one you would use to fix a hole in a door. Use two-part epoxy wood filler or all-purpose filler; epoxy cement usually isn't stiff enough for large repairs. Before you mix the material, cover the back of the hole with a piece of cardboard or plywood to hold in the filler. Secure the backing with screws if the reverse side won't be visible or with temporary spray adhesive if it will.
Mix the repair material and trowel it into the hole with a paint scraper. Scrape the repair flat, wait for the material to harden, and then remove the backing and sand both sides smooth. This repair won't be pretty, so you have to paint the particleboard if you want to camouflage it.