HeliCoil Screw Thread Inserts
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These are the standard HeliCoil inserts when installed, provides the hole with smooth free running 
threads. 

In their free state, HeliCoil Free Running Inserts are greater in diameter than the tapped hole into 
which they are installed. In the assembly operation the torque applied to the tang reduces the 
diameter of the leading coil and permits it to enter the tapped thread. When the torque or rotation 
is stopped, the coils expand with a spring-like action anchoring the insert permanently in place 
against the tapped hole. 

No staking, locking, swaging, keying, nor interference fit is required to retain HeliCoil inserts, 
thereby eliminating stress concentration in the parent material. The HeliCoil insert automatically 
adjusts itself, radially and axially, to any expansion or contraction of the parent material. 

HeliCoil Screw Thread Inserts - Types, Sizes, Lengths

Emhart Technologies HeliCoil Screw Lock Inserts have all the characteristics of HeliCoil Free 
Running Inserts but in addition, they feature a resilient locking mechanism which grips the bolt 
and prevents it from loosening under vibration or impact. 

The locking action is achieved by one or more of the coils of the HeliCoil insert having a series of 
straight segments, or chords. When the bolt enters this grip coil, these chordal segments flex 
outward creating pressure on the bolt. This pressure is exerted between the flanks of the bolt 
thread thus utilising the maximum contact area and minimising the unit pressure. 

HeliCoil Screw Lock Inserts permits frequent removal and reassembly of bolts without appreciable
loss of torque. They positively secure the screw against loosening caused by vibration and shock 
and they will not relax their grip on the screw even in tough metals such as cast iron, alloy steel, 
titanium, etc. 

Users enjoy cost savings in space, weight and money, through the elimination of lock wiring, lock 
nuts, lock washers, chemical compounds, plastic pellets/patches and other locking mechanisms.

Emhart Technologies HeliCoil Inserts are available in:

•Metric (Coarse & Fine)
•Whitworth (BSW, BSF, BSPF, BA)
•Unified Thread (UNC & UNF)
•Spark Plug 
•Pipe Thread

HeliCoil wire thread inserts are available in five insert lengths for each thread size - 1, 1.5, 2, 2.5 
and 3 times the nominal thread diameter of the screw or bolt.