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What is a Helicoil?

By STG Machine

STG Machine encounters lots of hardware on a daily basis, and one of the most popular pieces of hardware used in metal and plastic components is a helicoil.

What Is a Helicoil?

A helicoil is a coiled, metal insert that fits inside of tapped holes. Once the helicoil prong is broken off a screw can be fed in and out of the insert. Helicoils can be made out of a variety of materials including: stainless steel, steel, nickel and titanium.

Why are Helicoils Used?

Helicoils allow for screws to be inserted and removed without damaging the native threads on a part. Threads can get damaged over time, but helicoils can be replaced if they start to wear. Helicoils expand into the thread they are inserted into and they require a special thread to be cut.

How To Install a Helicoil

Purchase the appropriate size installation tool and screw the helicoil insert onto the tool. Then drive the helicoil a quarter to half-turn below the surface of the material. 

Where to Purchase Helicoils

Helicoils can be purchased at Mcmaster, Olander, Misumi and many other  hardware retailers.

How to Make a STI Tapped Hole

In order to install a helicoil you need to make a tapped hole large enough to accept the appropriately sized helicoil. The proper name for tapped hole of this size is: STI (Screw Thread Insert). An STI drill chart will inform you on the proper size drill to use in conjunction with an STI tap. Please reference the chart below from Balax as an example.


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