Heli-Coil STI (Screw Thread Insert) taps are used for general and machine operations. The standard STI tap can be used as a basic tool to create threads ideal for threaded inserts. It is recommended that these taps are used with a CNC machine or other high-precision equipment in order to ensure a proper class of fit.


Accuracy of the finished thread when the insert is installed is dependent upon the accuracy of the tapped hole. If the finished tapped hole gages satisfactorily, the installed insert will be within the thread tolerance.

Heli-Coil offers STI taps in four styles:

  • Standard Plug (4-Thread Chamfer): Easy starting for through-holes and blind holes
  • Standard Bottoming (2-Thread Chamfer): Ideal for blind holes drilled to a minimum depth
  • Spiral Pointed Plug (4-Thread Chamfer): Free-cutting for use in long through-holes and in blind holes with chip clearance
  • Spiral Flute Bottoming (2-Thread Chamfer): Pulls chips out of deep or blind holes in soft materials (not available for metric sizes)

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The availability of the products described on this site, and the product descriptions, may vary from country to country. Consult your STANLEY Engineered Fastening Account Executive or your local distributor for specific product information.