How to Use Thread Chasers and Inserts to Repair Stripped Bolt Holes

stripped bolt hole

Source I Hugo Cardoso

Chaser kits and thread inserts can restore stripped bolt holes in your vehicle.

Virtually everything on your vehicle is held together with nuts and bolts. Each time you unbolt something and put it back together, you stand a chance of stripping the threads. A stripped bolt is a simple fix: remove it and replace it with a new bolt. Stripped bolt holes, however, take some creativity to address.

You may be tempted to take the "close enough" approach to the situation. If you don’t fix stripped threads, however, you won't be able to properly tighten the bolt, and the connection will fail over time. Rethreading a bolt hole is an essential skill any automotive DIYer can master. We'll provide the tips and tools you need to get started.

What are thread chasers?

If your threads aren't completely destroyed, you can try "chasing" the threads, using some grease and a thread chasing tap. The thread chaser cleans away rust and defines the threads without removing any metal. This is especially helpful in locations like the engine, where loose metal filings could cause damage.

What are thread inserts?

When thread damage is too severe to be saved with a thread chaser, you can completely fix stripped threads with coil-type thread inserts. Inserts provide a newly threaded hole (with strong steel threads) that accepts the original size bolt. Inserts are installed by drilling the damaged thread hole slightly oversize, tapping it with a larger tap, and screwing in the new thread insert coil. Read on for more details.

Vehicle System
Tools & Parts
Skill Level
Beginner

This is a good project for new DIYers

Time to Complete
30 minutes
  1. Remove the bolt. To remove a bolt with stripped threads, drill the center of the bolt and use a bolt extractor.

  2. Clean the existing threads on the bolt hole using penetrating oil, some compressed air, and a clean rag. A shop-vac can be handy for this step as well.

  3. Drill the bolt hole oversized for the tap. The drill size is listed on the package. Use a drill block to keep the newly drilled hole straight. Be sure to keep the tap coated with cutting oil and to continually back the tap up to clear any metal filings.

    Note: you'll need to be especially careful about filings if you're working on the intake manifold or any other area where filings can be ingested into the engine.

  4. Screw the thread insert all the way onto the installation tool. The tab on the bottom of the thread insert should be engaged on the end of the tool.

  5. Coat the thread insert with a thread locking compound and screw it into the newly tapped threads until it is flush with the sealing surface. Use needle-nose pliers to snap off and remove the coil's tab.

    While this isn't a difficult job for anyone with mechanical skills, you will need to be patient and take it slow, especially when it comes to using a drill block to drill out the old bolt hole.

  6. Pro Tip

    When thread damage is too severe to be saved with a thread chaser, you can completely fix stripped threads with coil-type thread inserts.

Last updated July 6, 2017

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