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What are the four basic helical coil designs?

• Tanged free-running coils: They feature a stainless steel coil for preventing corrosion and can be used for rapid repair of damaged threads. They adhere to military and aerospace standards.
• Tang-free free-running coils: They are identical to tanged free-running coils, but have no tang at the bottom. They feature a unique insert-driven notch for screw-in installation and remove the need to detach the tang before inserting the bolt.
• Tanged screw lock coils: These helical coils feature a straight segment in the coil that is flexed outward, producing pressure on the bolt and retaining torque to ensure the bolt's position. They are designed to maximise the contact area by applying pressure between the flanks of the bolt thread.
• Tang-free screw lock coils: These have a similar design as tanged screw lock helical coils, but instead of a tang, they employ a driving notch for installation.

Why are some thread inserts larger in diameter than the tapped hole before installation?

Some thread inserts have a slightly larger diameter than the diameter of the tapped hole before installation, as the installation tool decreases the leading coil's diameter when it applies torque to the insert's prong / tang for easy installation. Once the threaded insert is installed, it acts like a spring and expands outward onto the material for strong anchoring.

How to choose the length of a helical insert?

The helical insert length should be at least as long as the desired screw diameter. Users may also choose inserts having longer lengths for increased strength. The exact insert length can vary, depending upon the application & the material. Materials like steel do not need long inserts, but for soft materials like aluminium, a longer insert is preferred.

Can thread inserts be removed once installed?

Yes, some thread inserts can be removed using removal tools that attach to them & unwind them in the direction opposite to that used during installation.