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FAQs

Answers to your technical and commercial questions about bigHead fastening products.

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    Closed sighted collar

    • Can all bigHead fasteners come with a closed sighted collar?

      No. This customisation applies only to F2/SF2 internally threaded collars with sighted Head types S20, S23, S30, S32, S38A and ST38A.

    • Do load limits or torque settings change for closed sighted collars?

      No. Standard collar fixing load limits (FLL and WLL) and torque recommendations apply.

    • How do I calculate the maximum usable thread length (Le)?

      Subtract the unusable length (Lu) from the collar length (L): Le = L – Lu.

    • What are the compatible standard collar lengths for this customisation?

      M4: 10 and 15 mm

      M5 to M8: 10, 15 and 20 mm

      M10 and M12: 15 and 20 mm

    • What is the main advantage of a closed sighted collar?

      The blind shank design prevents fluid or moisture ingress, protecting the thread from adverse effects due to environmental exposure.