How do you repair a stripped machine screw hole in metal or plastic?

How to Repair a Stripped Machine Screw Hole in Metal or Plastic

As engineers in manufacturing, we often encounter the issue of stripped machine screw holes in metal or plastic. This can be a frustrating problem that hinders the functionality of the equipment or machine.

However, with the right tools and techniques, it is possible to repair a stripped machine screw hole effectively. 

Tools and Materials Needed

Before we delve into the repair methods, let’s first gather the necessary tools and materials. Here is a list of items you will need:

• Drill and drill bits
• Tap and die set
• Thread insert kit
• Screw extractor
• Epoxy adhesive
• Filing tool

Method 1: Re-Tapping the Hole

One of the most straightforward ways to repair a stripped machine screw hole is by re-tapping the hole. This method involves using a tap and die set to create new threads in the damaged hole. Here’s how to do it:

1. Choose the appropriate tap size that matches the original screw thread.
2. Secure the tap into a tap wrench and lubricate it with cutting oil.
3. Carefully insert the tap into the damaged hole and turn it clockwise to cut new threads.
4. Remove the tap and clean out any metal shavings from the hole.
5. Test the fit with a new screw to ensure the threads are properly aligned.

Re-tapping the hole can be an effective solution for minor stripping issues where the threads are not heavily damaged. However, if the hole is severely stripped, you may need to consider alternative methods.

Method 2: Using Thread Inserts

Thread inserts, also known as helicoils, are small metal coils that can be inserted into a stripped hole to create new threads. This method is ideal for holes that have extensive damage or are oversized. Here’s how to use thread inserts:

1. Drill out the damaged hole to the specified size for the thread insert.
2. Insert the tap from the thread insert kit into the hole and create new threads.
3. Place the thread insert onto the installation tool and screw it into the newly tapped hole.
4. Use a tang break tool to remove the tang from the insert and secure it in place.
5. Test the fit with a screw to ensure the repair is successful.

Thread inserts provide a durable and long-lasting solution for stripped machine screw holes, ensuring a secure hold for the fastener.

Method 3: Using Epoxy Adhesive

If the stripped hole is in a non-structural part or made of plastic, epoxy adhesive can be a practical solution. Here’s how to repair a stripped hole using epoxy:

1. Clean the damaged hole and the surrounding area with a degreasing agent.
2. Apply epoxy adhesive to the threads of the screw and insert it into the stripped hole.
3. Let the adhesive cure according to the manufacturer’s instructions.
4. If necessary, use a filing tool to smooth out any excess adhesive and ensure a flush surface.

Epoxy adhesive can provide a temporary fix for stripped holes in plastic or non-structural components, but it may not be as durable as other methods for metal materials.

Conclusion

Repairing a stripped machine screw hole in metal or plastic is a common challenge in manufacturing.

By using the right tools and techniques, such as re-tapping the hole, using thread inserts, or employing epoxy adhesive, you can effectively restore the functionality of the equipment or machine.

Choose the method that best suits the severity of the stripping and the material of the component to ensure a successful repair. Remember to always test the fit with a new screw to confirm the repair has been completed accurately.