FAQs

Selecting screw lengths for bigHead collar fasteners

• Do washers or flanged screws affect screw length selection?

  Yes. Any component between the screw head and the collar adds to the installation stack thickness and must be included in the calculation.

• How do I know if my screw is long enough for a sighted collar?

  Ensure the screw length meets or exceeds the required minimum engagement: L + installation stack + 1.2 mm (if fastening from the Head side).

  The examples in this guide show how to calculate it.

• My application requires a specific engagement length. Can I request a custom collar design?

  Yes. bigHead offers custom collar options – including closed, sighted, length variant, and hybrid options. We can help you choose the optimal collar customisation for your application.

• What happens if the screw is too long in a blind collar?

  The screw will bottom out against the closed end, deforming or damaging the bigHead. This is considered misuse and may result in product failure.

• Why is tip clearance (Lu) different for each thread size?

  The clearance allowance scales with thread diameter and pitch to maintain sufficient deformation protection. Larger threads require greater tip clearance.