Stripped screw holes in aluminium cause loose screws and weak joints. Fixing them is easier than you might think. This guide gives you simple, effective ways to repair stripped holes safely and get your project back on track quickly and reliably.
Why Do Aluminium Screw Holes Get Stripped?
Aluminium is softer than steel, so its threads wear out faster under stress. Common reasons for stripped holes include:
- Screws tightened too hard or beyond recommended torque
- Using the wrong size or thread type for the hole
- Removing and reinserting screws many times, which wears the threads down
- Shaking, vibration, or shock loads loosening screws over time
- Poor thread cutting or misaligned holes during the original installation
Understanding why holes strip helps you avoid mistakes and choose the best repair method for lasting results.
Stay Safe and Prepare Well
Safety should always come first before any repair work. To protect yourself and your workspace:
- Wear safety goggles and gloves to shield your eyes and hands from metal shards and sharp edges.
- Aluminium dust can be harmful and combustible; work in a well-ventilated area and use a mask if necessary.
- Clamp your aluminium piece firmly so it doesn’t move while you work on it.
- Clean the area around the hole to remove dirt, grease, or oil that could interfere with repairs.
- Collect metal shavings safely in a container and dispose of them properly to avoid injuries or contamination.
- Check the metal carefully for cracks or excessive damage, as this could mean the part needs replacement rather than repair.
Thread Sizes and Torque Basics
Using the correct screws and threads is critical for a strong fix:
- Most modern aluminium parts use metric threads, such as M3, M4, or M5 sizes.
- In some cases, especially in American-made parts, Unified Thread Standard (UNC or UNF) threads are common.
- Avoid older thread standards like British Standard Whitworth (BSW), as they are rarely used today.
The screw must fit the hole exactly; thread pitch and diameter must match perfectly for a secure hold.
Torque is how tightly you turn a screw. Too much torque can strip threads, while too little lets screws loosen.
- As a rough guide, M5 screws in aluminium usually need about 4 to 6 Newton-meters of torque, but this varies widely depending on alloy type, screw material, and thickness.
- Always check manufacturer or engineering guidelines for the exact torque to use in your project.
How to Fix a Stripped Hole
1. Use a Helicoil Insert
Helicoils are metal wire coils that create new, strong threads inside stripped holes, restoring them to near-original strength.
Steps to follow:
- Select a Helicoil kit that matches your screw’s size and thread pitch.
- Drill out the damaged hole using the specific drill bit included in the kit.
- Tap new threads carefully with the supplied tap, applying some oil or lubricant to make tapping smoother and avoid damage.
- Insert the Helicoil coil into the hole with the installation tool until it sits flush with the surface.
- Some Helicoils come with a small tang (a tab) that you need to break off carefully with a punch; always follow the kit’s instructions exactly.
- Finally, reinstall your original screw. It should fit tightly and hold firmly.
Helicoils offer a strong and durable repair that lasts a long time under regular use.
2. Tap a Larger Thread and Use a Bigger Screw
If Helicoils aren’t available or suitable:
- Choose a tap slightly larger than your stripped hole to cut new threads.
- Tap the threads straight and carefully to avoid damaging the aluminium further.
- Use a screw that matches the new, larger thread size.
This method works well but may require you to adjust or replace the mating parts to fit the bigger screw.
3. Try Thread Repair Liquids (Temporary Fix)
For quick fixes or light-duty applications:
- Thoroughly clean the hole to remove grease and debris.
- Apply a metal-reinforced epoxy or special thread repair liquid according to the product instructions.
- Insert the screw while the compound is still wet and allow it to cure fully.
This repair is temporary and not recommended for heavy loads, high vibrations, or safety-critical parts.
Quick Temporary Tricks
If you need a very fast, temporary solution without tools:
- Wrap a few layers of Teflon (thread) tape tightly around the screw threads. This adds friction and helps the screw grip better in a loose hole.
- Insert thin strands of copper wire into the hole before driving the screw in. The wire fills gaps and improves the hold.
These methods can hold for light duty but should be replaced with proper repairs as soon as possible.
Closing Holes You Don’t Need
If a screw hole is no longer needed or you want to seal it permanently:
- Use TIG welding to fill the hole in aluminium. TIG welding provides a clean, strong fill.
- After welding, smooth the surface with sanding tools or a Dremel to restore a flush finish.
- Because aluminium welding requires skill and proper equipment, it’s best to hire a professional welder for this job.
Tools and Costs
| Tool or Material | Price Range (USD) | Notes |
|---|---|---|
| Helicoil Kit | $18 – $65 | Depends on size and brand |
| Tap and Die Set | $25 – $130 | Quality affects price |
| Thread Repair Liquid | $12 – $40 | Choose one rated for aluminium |
| Safety Gear | $6 – $25 | Includes goggles, gloves, masks |
| Welding Service | Variable, from $60+ | Depends on location and job |
You can buy tools from hardware stores, auto parts shops, or online retailers.
Tips to Avoid Common Problems
- Always start screws by hand to avoid cross-threading and damaging new threads.
- Use guides or drilling jigs to keep taps straight and accurate.
- Use a torque wrench to tighten screws to the recommended setting.
- When repairing multiple holes, space them apart to keep the part’s strength.
- If an insert or repair fails, double-check the hole size and thread quality before trying again.
How to Prevent Stripped Holes in the Future
- Always use the correct screw size and matching thread pitch for your aluminium parts.
- Follow torque specifications carefully to avoid overtightening.
- Lubricate screws lightly before inserting to reduce friction and thread damage.
- Avoid repeatedly removing and reinserting screws in the same hole when possible.
Final Thoughts
Fixing stripped screw holes in aluminium is straightforward with the right tools and care. Follow safety guidelines and pick the best repair method for your needs. Consider the load and function of your part before repairing. If you are unsure or the damage is severe, seek professional help.
Feel free to ask for step-by-step photos or product recommendations to make your repair easier and more successful.
Read More: