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What causes a stripped screw hole?
A stripped screw hole occurs when the threads inside the hole become damaged or worn down. This prevents the screw from gripping properly and results in spin out or loosening. Some common causes of stripped screw holes include:
- Over-tightening – Applying too much torque when driving in a screw can shear off the threads in the hole.
- Incorrect screw size – Using a screw that is too small or too large for the hole can damage the threads.
- Poor quality materials – Screw holes drilled in low density woods, plastics or metals are more prone to stripping.
- Cross-threading – Forcing in a screw at an angle can damage the threads in the hole.
- Repeated use – Normal wear over time from repeatedly driving screws in and out of a hole can cause stripping.
- Corrosion – Rust, corrosion or rotting of the material surrounding the screw hole can weaken the threads.
How can you tell if a screw hole is stripped?
Here are some signs that indicate a screw hole has become stripped:
- The screw spins in the hole without tightening when torque is applied.
- The screw loosens and falls out with minimal force or vibration.
- Debris from damaged threads can be seen under the screw head.
- The driving tool, such as a screwdriver, spins freely in the hole without resistance.
- The screw head sinks into the material when tightening instead of stopping flush.
- Cracks or damage around the hole are visible.
If you encounter any of these issues when trying to drive in a screw, it likely means the threads inside the hole are compromised and no longer providing a tight grip.
How to fix a stripped wood screw hole
For stripping in soft woods, a few simple fixes can reshape damaged threads or create new ones for a solid hold. Here are some options for repairing a stripped wood screw hole:
Use a larger screw
Switching to a screw with a wider shank and larger threads can allow it to bite into the wood around the damaged hole for grip. Make sure the larger screw is not so big that it splits the wood.
Fill the hole with a hardwood plug
Gluing a precisely fitted hardwood plug or dowel pin into the stripped hole can re-cut new threads when you drive in the original screw. Maple, oak or walnut are good plug material options.
Insert wooden toothpicks or matches
Dip toothpicks or matchsticks in wood glue and pack them tightly into the hole. Break them off flush after the glue dries. The fragmented wood will create grip for the screw like a makeshift anchor.
Use an insert nut
Insert nuts come in a range of sizes and screw thread types. Hammer one into the stripped hole then drive your screw into the nut’s undamaged threads.
Apply epoxy or wood filler
Injection epoxies designed for stripped screws can rebuild the damaged hole. Apply with the supplied nozzle and allow to fully cure before re-driving the screw.
Use a sliver screw extracter
This tool has a fluted end that grips into the hole as you turn the tool. It carves fresh threads to provide grip for the screw. Apply a drop of oil first to ease insertion and turning.
Drill pilot hole for larger self-tapping screw
Enlarge the stripped hole with an appropriate drill bit then use a larger self-tapping screw, which will cut new threads into the hole.
| Method | Pros | Cons |
|---|---|---|
| Larger screw | Simple fix with common item | Risk of wood splitting if too large |
| Hardwood plug | Repairs and strengthens stripped hole | Precise sizing and fitting required |
| Toothpicks or matches | Cheap and readily available | Not the strongest method |
| Insert nut | Quick repair with new threads | Nut size must match screw |
| Epoxy | Bonds strongly and rebuilds hole | Must wait for full cure time |
| Screw extractor | Cuts fresh clean threads | Specialized tool required |
| Self-tapping screw | Permanent solution | Requires drill for pilot hole |
How to fix a stripped metal screw hole
Stripped holes in metal can be trickier to repair than with wood. But several techniques can restore grip so your fastener stays put:
Use a screw extractor
As with wood holes, an extractor bit can re-cut fresh threads in damaged metal holes. Apply lubricating oil first and use the lowest speed on your drill.
Install a threaded insert
Hammer in a coiled metal insert matched to your screw size into the stripped hole. New compatible screw threads are now created.
Use an oversized screw
Swap the original screw for one with larger diameter threads. The bigger screw can bite into the stripped hole’s metal for holding power.
Put a nut on the opposite side
Place a nut on the screw after it passes through the stripped hole. Tighten the nut against the opposite surface to hold the screw in place.
Apply thread lock glue
Applying a few drops of high strength thread locking glue before driving the screw can bond it into a damaged hole for a solid grip.
Use a helicoil insert
A helicoil insert has coiled wire that matches your fastener’s thread size. Install with a special tool into the stripped hole to create fresh threading.
Weld a nut over the hole
Tack welding a nut directly over the stripped hole can allow you to drive a matching screw into the nut for repair. Grind excess weld smooth afterwards.
| Method | Pros | Cons |
|---|---|---|
| Screw extractor | Quickly cuts new threads | Specialized bit required |
| Threaded insert | Durable permanent repair | Hammering required for install |
| Oversized screw | Simple technique | Larger hole required |
| Nut on opposite side | Fast technique with basic hardware | Access to both sides needed |
| Thread lock glue | Bonds screw in place | Permanent install, hard to remove later |
| Helicoil insert | Professional grade repair | Specialty installation tool needed |
| Weld nut over hole | Strong permanent fix | Welding equipment required |
Tips for preventing stripped screw holes
An ounce of prevention is worth a pound of cure when it comes to stripped screw holes. Keep these tips in mind:
- Use the correct size screw for the hole and material thickness.
- Drill pilot holes in dense woods and metals to guide screws.
- Avoid high torque over-tightening that can shear threads.
- Match screw heads and driving bits for maximum grip.
- Ensure screws align straight when driving them in.
- Periodically inspect and tighten screws as needed.
- Consider pre-drilling larger clearance holes for materials prone to stripping.
Conclusion
Stripped screw holes are a common but repairable issue when working with woods or metals. With the proper techniques matched to the affected material, you can often fix a stripped hole and restore full threaded grip for your fasteners. Prevention via careful screw driving and inspection will also help avoid problematic stripping that requires repairs down the road.