Quick Methods For Repairing A Stripped Screw Hole
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They never believe you. You can tell your kids 100 times not to slam a door or swing on the cabinetry, but little Polyanna with all her inexperience isn't going to believe you until the thing gives way. And it will, sooner or later, because there's only so much a screw can take. And, eventually, it pulls out of its substrate, usually wood, which means that the screw hole is now roughly the same diameter as the screw threads' outside edge. When this happens, the screw no longer has any holding power to speak of. And it can happen for a number of reasons; it's usually excessive stresses, like Poly's gymnastics, but sometimes even small stresses with a lot of leverage can damage a screw hole's internal threads. And sometimes deterioration plays a role, especially when the screw hole is exposed to the elements and, in particular, to water.
Unlike a bolt, which uses a nut to get its holding power, a screw relies on threads in at least one of the materials it's attaching to (in the case of wood screws and self-tapping screws, these female threads are made at the time of first use in a particular spot). When those threads are stripped, the screw becomes useless at holding things together, and that means that things are in the process of falling apart. If what's falling apart is your front door or the point where your aerial silks attach to the ceiling, you're in a bit of a jam.
How you handle it depends on whether your screw hole is in wood or metal. We'll talk about stripped screw holes in wood first, since that's the most common situation, then cover a few common fixes for metal.
When the stripped screw hole is in wood, one of the more obvious solutions isn't a screw hole repair at all, but the use of a thicker or longer screw. This can work, but there are some caveats with this approach that you should be aware of.
When you're trying out a longer screw because the old screw is no longer holding, you want to be sure you're screwing into enough wood to be effective. The most common stripped hole situation is probably hinge screws, which are dealing with quite a lot of stress. The problem is that your door's hinge jamb (the wood part of the door frame to which hinges attach) isn't always flush against the jack stud next to it. (Spacers should be positioned where the hinges are, but you shouldn't count on it.) This means there might be a gap you can't see just beyond the jamb, so a screw should be long enough to cover that gap and still have enough thread left to secure the hinge. This is a good thing to keep in mind whenever you can't see exactly where a screw is going.
Using a thicker screw has its own potential problems. If you're attaching something with a hole that's pre-drilled in metal, the most likely problem is that the new screw is too large for the hole you have to work with. An even more common problem is that the head of your replacement screw is too large for the countersunk (beveled) holes in your hinge, meaning the screw won't seat properly and might prevent your door from working properly.
If you don't have these sorts of restrictions to worry about, using a longer or thicker (or both) screw might just do the trick.
Another common way of dealing with stripped holes in wood is to fill the hole with some wooden material that will hold to the original hole while allowing the screw to cut new threads in your repair material. For example, you can pack some wooden matches (ideally dipped in wood glue) into a screw hole, cut the part that's sticking out off flush, and then drill a new pilot hole in your matches for your screw. Other common choices include toothpicks, wood scraps, wood shavings, chopsticks, golf tees, and even paper towel.
This is basically an improvised version of the correct repair method, which is coming up next, and it's more likely to work without requiring a trip to the hardware store. One other advantage is that you don't usually have to drill out the old hole before making the repair; just shove your matchsticks (or whatever) directly into the old hole.
There are a few gotchas to be on the lookout for. First, trimming your wood material flush with your hole isn't as simple as it sounds. It can be difficult to do with most saws, especially if the hole is in an awkward location. There are inexpensive flush-cut saws designed for this purpose, or you can use a flexible blade like a hacksaw blade without a handle to make the cut, then sand out any imperfections. You'll also want to be sure you drill your pilot hole properly. An over-large pilot hole will cause you to start with an almost-stripped hole right from the beginning.
Sometimes you'll see a "hack" advising you to try using a pencil as the filler material for your stripped hole. This can work, but note that non-round pencils won't always make great contact with the surrounding wood, and any paint or other finish on the outside of the pencil might make wood glue not adhere well.
The proper way to fill a stripped hole in wood is to enlarge the hole and glue a dowel or plug of a matching diameter into the new hole. The process is simple enough: find a round dowel at least as wide as the external thread width of your screw, then find a drill bit of matching diameter. Drill your new hole directly into the old one. Coat the dowel in wood glue to the depth of the hole, then drive it into the hole. Cut the dowel off flush, then drill a pilot hole for your screw. Pilot holes are especially important for hardwood dowels. If you're fixing hinges, it's a good idea to use a center punch or a special hinge bit to properly center the pilot hole where your hinges require screws; off-center pilot holes can result in screws that aren't properly flush with the hinges, which can interfere with the door's closing.
The most likely problem with this approach is your drill bit not matching the diameter of your dowel. Don't compromise here; even a slightly loose dowel could interfere with the holding power of your new screw hole.
This fix is usually stronger than the original screw hole was when it was created, because dowels are often hardwood driven into softer wood, and the wood glue is famously stronger than pine and similar woods it's used in. And it's not just a fix for hinges. Anywhere that strength, appearance, or both is important, this is a good solution.
The stuff you jam into a stripped hole to accept new threads from your screw doesn't have to be made of wood. There are some very good improvisations around that use plastic instead, and the easiest of these might be to use a length of cable tie (or "zip tie") instead of toothpicks and the like.
This is not an ideal solution, and should probably only be used for low-stress applications. Any wood glue (and even other adhesive) you might use is unlikely to properly adhere to the cable ties, meaning they could pull out (along with your screw) fairly easily. To the extent you can control it, use the rougher side of the cable tie in contact with the old screw hole; the friction might improve the holding power, and your screw will automatically create the right threads in the smoother side.
You might also find it difficult to cut the zip ties flush with your work surface. Since a screw head will cover most of the filler material, this might not be a significant problem.
Used correctly, plastic wall anchors are an improvement over the cable tie approach. These are the cone-shaped plastic inserts that you typically drive in with a hammer. They have a threaded screw hole, and when a screw is driven into them, they expand to fill the hole as tightly as possible. Keep in mind that these and similar anchors (like winged anchors, toggle bolts, and others, are technically hollow wall anchors. They are designed mainly for use in drywall, and often rely on the board they're driven into being no more than, say, ⅝-inch thick. There are similar products, such as Screw It Again and the FIREFLYWEB Screw Door Security Hardware Repair kit, that are designed specifically for use in wood.
Threaded drywall anchors can sometimes work in wood, though you should probably stick with the zinc versions as the plastic/nylon varieties are unlikely to properly cut threads in lumber. These anchors are typically sized for a certain size of sheet metal screw, so take care that your anchor matches the screw you need to use.
Sometimes anchors are flanged in a way that requires them to be countersunk when used in wood. Because these flanges are of different shapes, you'll have to figure out the best approach to countersinking your screw hole on the fly. Often a simple countersink bit can be used, but for more square flanges you might need to drill a shallow countersink with a larger drill bit instead.
Threaded inserts are devices, typically made of metal, that convert a hole from a self-drilled type (as you might usually see with wood screws or self-tapping metal screws) to use threads pre-cut in the insert. These inserts are usually threaded for common bolt thread sizes, and you're basically replacing your wood screw with a threaded insert (which provides threads that interact with your wood) and a bolt (which attaches to the insert).
The big factor here is the holding power of the insert in the wood itself, and threaded inserts can be very strong. Unlike nuts and t-nuts, which we'll discuss below, threaded inserts don't always have tension to hold the bolt threads securely against the insert's internal threads, so the bolt can be particularly susceptible to backing out of the threaded hole when vibration is present. Using a thread-locking compound or a lock washer can help in this situation.
While threaded inserts are typically strong, if you have doubts about the connection between the insert and the wood, you can use epoxy to strengthen the bond.
Over the years, it's become increasingly common for woodworkers to reach for Cyanoacrylate (CA) glue, better known by the trademark Super Glue, for certain tasks. Filling your stripped hole with an adhesive like CA glue can sometimes work for screw holes that aren't tasked with supporting a bunch of weight, and so is one good approach for smaller jobs.
Like CA glue, two-part epoxies can be used to fill stripped screw holes, and these wood and automotive fillers tend to be a lot stronger and more durable than CA glue. In addition to general-purpose epoxies, there are specific formulations for wood that should adhere better. You can also use automotive formulations, which are sometimes strengthened with a material like fiberglass. You can use epoxy to glue in an anchor or similar, or you can simply fill the screw hole, pre-drill it with a pilot hole, and then cut new threads in the epoxy itself by running your screw into the cured epoxy.
There are a few other approaches to (or workarounds for) repairing stripped screw holes in wood: some variants of ideas already mentioned, along with unique ideas that can work just fine in the right situations. There are commercial products that are worth considering, and the most common is the metal mesh approach found in products like the Mr. Grip Screw Hole Repair Kit and others. Based on their instructions for use, the Mr. Grip kits basically use strips of metal screen in the same way toothpicks are used to repair screw holes: bits are shoved in, and they both grip the screw hole walls and form threads around the screw, effectively un-stripping the hole. (There's also a Joint Repair Kit for repairs like unthreaded chair legs, though you'd be better off with a bottle of wood glue in that instance.) Another commercially available product is the plaster mesh disc that's used to wrap around anchors to effectively thicken them and strengthen the bond with the wall; these are primarily for drywall, but according to the instructions can also be used with other materials like wood.
Fringe Screws are another product that attempt to solve the stripped hole problem specifically for door hinges by basically mismatching the screw threads and head sizes. Fringe Screws have oversized threads to grip in stripped holes, but the head itself remains the smaller standard size, so that it won't interfere with the functioning of the hinge.
Among the very best solutions is one that isn't a hole repair strategy at all; it's simply relocating the hole somewhere else. This won't work in some situations; it would be untenable where balance required a specific location or where matching pieces would get out of whack, as with door hinges. But in some circumstances, you can instantly regain all the strength with very little work by simply putting a new hole somewhere else.
In some cases, it's possible to replace a screw with a bolt and nut, which thread together and get their strength from that junction and none from threads in the wood itself. But it isn't always a possibility for various reasons, the most common probably being that you usually need access to both sides of a hole to attach a nut to your bolt., or when the nut and the bit of extended bolt it attaches to would interfere with some other mechanism. But when it does work, using a bolt/nut in place of a screw can be a helpful approach.
T-nuts are basically nuts that are used in wood, but the nut is countersunk into the wood to prevent the problem of the nut getting in the way. They act like threaded inserts that are hammered in from the other side. Note that you still need access to both sides of a workpiece to use them.
Certain types of wall anchors are, basically, bolt/nut combinations. Probably the most familiar of these is the drywall toggle bolt, a type of hollow wall anchor in which the nut includes wings that spring apart and grip the opposite side of the workpiece from your bolt head. This eliminates the problem of needing access to both sides, but it does still require a hollow wall to work.
The bolt/nut screw fixer solution is probably most commonly seen when working with metal, because screwing into sheet metal can be a fairly weak joint by comparison. You still need to pay careful attention to bolt length, though, especially when working with anything mechanical (a lawn mower, for example). Don't use overlong bolts that can interfere with workings on the nut side of the bolt.
Of course, stripped holes don't just happen in wood. If you're dealing with a stripped hole in metal, the problem is a little different and a little more complicated. Some of the approaches are similar, however, such as using a thicker screw to replace the original. This can work, but often doesn't.
An example might be instructional. Two pieces of sheet metal are often joined via a screw through a larger hole in the piece on the side with the screw head, and self-cut threads in the other piece. So the screw is inserted through the large hole and threaded into the other piece and tightened. When you're dealing with a thin gauge of metal and that tighter, threaded hole becomes stripped, your options are limited. If there's enough material around the large hole, you might be able to use a thicker screw to replace the original. Just keep an eye on how much room you have, pre-drill the large hole even larger if necessary, and use a self-tapping screw to make cutting the new threads easier.
When the second piece of metal is thick enough, the ideal solution is often to cut new female threads. This is also the most complicated solution in terms of knowledge required, tools needed, and perhaps risk of failure. After making sure you have enough room in both pieces for your new, larger fastener, and that the threaded side is sufficiently thick to hold the larger threads, you'll need to use a tap of the correct size to cut new threads in it.
This is a straightforward process, but you will need the tap, a handle for turning it, a properly sized and metal-compatible drill bit for pre-drilling the hole, some thread-cutting oil to lubricate the effort, and a properly sized machine screw. Machine screws are screws that are threaded like a bolt, without a taper. You can use them with nuts, but they are often screwed directly into a threaded workpiece.
There are a few solutions around that are similar to anchors, and these have their own set of use cases. Helical coil inserts are spring-like mechanisms that can be inserted into thick metal (like an engine block) to serve as new threads to replace damaged ones. They are analogous to threaded inserts used for wood, but add quite a bit of holding power and temperature resistance capabilities to the mix. These are commonly used for fairly demanding mechanical applications.
Rivet nuts are an interesting combination of many of these approaches, and are very useful for creating a secure hole into which a screw may be driven. The rivet nut is a threaded insert that you drive into a hole that's been enlarged to a specific size, and then affix into place with a hand-operated rivet gun. This can be accomplished with access to only one side of the workpiece. Rivet nuts are inexpensive and effective, but do require a fair amount of physical force to install.
It's possible in some situations to eschew the screw altogether, replacing it with a pop rivet. This works when relatively thin materials are joined to each other, and usually when you only have access to one side of the materials. Even if you're not familiar with pop rivets, you've probably seen them in situations where two pieces of sheet metal are joined and no one has any plans to take them apart again. Aluminum downspout components are often joined with pop rivets, for example, although they can also be assembled using sheet metal screws instead.
As with rivet nuts, pop rivets are often assembled using a tool that requires a certain amount of physical force to operate, though there are pricier power versions. Drill out your workpieces, insert the shank of a pop rivet into your rivet gun, insert the rivet through your two holes, and squeeze the gun's handles until the shank snaps off, leaving the river in place. Pop rivets can be removed by drilling them out, but it's not a particularly quick process like unscrewing a sheet metal screw would be.