3591-5CN625 - Helicoil ® Threaded Insert by Stanley ® Engineered Fastening

The HELI-COIL 3591-5CN625 is a high-performance screw-locking tangless wire thread insert designed to create high-strength, wear-resistant internal threads in soft metal parent materials. Precision-formed from 304 stainless steel, this 5/16-18 UNC thread insert features a 2.0D nominal length with a plain finish, combining a tangless design with an exclusive locking coil mechanism that grips the mating bolt to prevent rotational loosening caused by severe shock and vibration.

Screw-Locking Mechanism utilizes a resilient series of chords on the central coils that exert strong radial pressure on the mating bolt, locking it securely without requiring lock washers or safety wire.

Tangless Design completely eliminates drive tangs, removing the risk of foreign object damage (FOD) and saving labor costs by eliminating tang break-off and retrieval steps.

304 Stainless Steel delivers superior corrosion protection, mechanical strength, and thermal durability across demanding aerospace, automotive, and industrial assemblies.

Bi-Directional Insertion features driving notches on both ends of the insert, allowing non-oriented installation to increase assembly speed and efficiency.

2.0D Nominal Length provides extended thread engagement depth to maximize load-carrying capacity and shear resistance in low-density materials.