HeliCoil Screw Thread Inserts

HeliCoil Inserts are helically wound, precision formed coils of extremely hard stainless steel (18-8) diamond shaped wire. When installed into a HeliCoil tapped hole, the insert provides permanent conventional screw threads.

HeliCoil screw thread inserts have a driving “tang” for installation which is notched for easy removal.

Free Running Inserts

The standard HeliCoil helically wound insert with precision-formed rounded coils and a diamond shaped cross-section. When installed, they provide the hole with smooth free running threads.

Screw-Lock Inserts

HeliCoil Screw Lock Inserts have all the characteristics of free running inserts but in addition, one or more coils in the middle of the screw lock insert are polygon shaped. These coils serve as a locking device by gripping the threads of the installed screw, effectively preventing the screw from loosening under vibration or impact.

HeliCoil Screw Lock Inserts permit 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.

Materials & Platings

Besides the standard 304 (18-8) stainless steel, HeliCoil inserts are also available in:

  • Inconel X-750
  • Nimonic 90
  • Phosphor Bronze
  • Nitronic 60
  • Titanium


  • Dry Film Lubricant (Mollylube)
  • Cadmium Plating
  • Zinc Plating
  • Silver Plating

Insert Lengths

HeliCoil inserts are available in lengths from 1 to 3 times the nominal diameter of the bolt or screw.

Insert Sizes

HeliCoil Inserts are available in:

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

HeliCoil TwinSerts

HeliCoil TwinSerts restore damaged holes to the original thread size. They are used for salvaging incorrectly tapped holes and holes that are stripped, off-centre, or damaged.

HeliCoil TwinSerts should be used when the oversize condition of the hole is beyond the corrective range of HeliCoil OverSize Inserts.

As the name implies, a HeliCoil TwinSert consists of two HeliCoil inserts - an Outer Insert, and an Inner Insert. The Outer Insert is always free running while the Inner Insert can be either free running or screw-locking.

HeliCoil TwinSerts are available in numerous nominal thread sizes.

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