Locking Heli-coil
Locking Heli-coil
(OP)
if a locking helix-coil is installed in a thru hole how to determine the locking side? My inspector has a part which calls out the insert to be installed from both surfaces. what is the best way to determin if the insert is installed from the correct surface?





RE: Locking Heli-coil
I take it you mean helical or Helicoil thread insert.
A helical thread insert with a deformed coil, the locking mechanism, locks from either direction. A through hole is good design practice, since it makes it easy to remove the tang. If it matters to you, you can specify the insert depth from one side, on your drawing.
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JHG
RE: Locking Heli-coil
Thank you very much.
RE: Locking Heli-coil
If you have a deep hole, you need a long heli coil that fills it entirely.
RE: Locking Heli-coil
First, if my memory is correct, the deformed thread locking feature of your helicoil is located at the middle of the insert length. It is good design practice to ensure that the installed mating screw extends a minimum of two thread pitches beyond the locking feature, which in your example using a 6-32 screw would be .063" min.
Second, to obtain the full design load capability from your helicoil, the insert's entire thread length must be engaged by the mating screw.
Third, you should check that the mating fastener has sufficient thread length to prevent the threads from "bottoming out" under the worst case dimensional/tolerance stack-up conditions expected. It can be hard to determine a screw that has just barely bottomed out on its threads from one that has been installed correctly, especially when using torque wrenching.
All of these things will be affected by any difference in axial location of the insert relative to the attachment interface resulting from the installation procedure described. These seemingly minor design details can cause major problems unless you pay attention to them.
RE: Locking Heli-coil
I strongly agree with this point. It does make the position of the locking element irrelevant.
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JHG