Common Thread Repair Inserts

Here we'll address three of the more common types of thread repair inserts.

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Helical 

Helical inserts consist of a diamond-profile coil of wire. A few things to remember when using this type of insert:

  • Requires a special tool to install

  • Requires a non-standard tap

  • Has a tang that must be removed after installation

  • Can be stacked for more thread engagement

Although these require a special installation tool and tap, they can be purchased in a kit that contains all of the required equipment. 

I like the flexibility these inserts offer. If you have a shallow hole with damaged threads, simply trim some of the coils from the top to match your depth. If your thread repair is deep, you can stack these for additional thread engagement. 

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Key-Locking

Key-locking inserts do not require a special tap prior to installation, but they do require a special tool to drive in and secure the keys.

Helical inserts use spring tension and friction to prevent loosening from vibration. Key-locking inserts actually drive keys into the threads along the side of the insert, making it virtually impossible for the insert to back out or thread in further once installed. 

These inserts cannot be stacked or trimmed to fit your application. Flexibility is not their strongpoint. Their strength lies in their mechanical thread-locking feature.  

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Easy-to-Install

As the name implies, these have the easiest installation of the three inserts featured here.  They do not require a special tap or special tool for installation (although one is available). 

These inserts come with a thread-locking compound already in place, so you can have some peace of mind about applications with lots of vibration. Not all thread-locking compounds are created equal. Do your research to make sure that this will work for you. 

That being said, I like that these can be installed with a standard tap and screw driver. This makes them fairly attractive for hobbyists on a budget.