FAQs

Customising bigHead fasteners

• Are all bigHead products compatible with every coating option?

  Compatibility depends on the geometry of the fixing and the coating‑process limitations (e.g. residue traps, tumbling witness marks). Get in touch with us for advice on compatibility.

• Are load limits for reverse weld collars the same as standard F2/SF2 collars?

  No. The reverse weld orientation creates different load paths. We can provide load-limit values and tightening torque recommendations on request to support correct application.

• Are there different tolerances for custom thread lengths?

  No. Custom thread lengths follow the same dimensional tolerances as our standard stud and collar products. This ensures consistent fit, function, and installation performance.

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

  No. This customisation applies only to F2/SF2 internally threaded collars used with blind Head types B20, B23, B30, B32, B38A and T38A.

• 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.

• Can bigHead provide installation strength data for large round Head customised products?

  Yes, but only for application‑specific enquiries. Adhesives and embedment designs vary widely, so we can’t publish direct data comparisons between standard and customised products.

• Can bigHead provide installation strength data for large square Head customised products?

  Yes, but only for application‑specific enquiries. Adhesives and embedment designs vary widely, so we can’t publish direct data comparisons between standard and customised products.

• Can I combine a large round Head with a non‑standard fixing length or size?

  Not through our customisation service – but we’d love to guide you through our Create service and create a new solution for you.

• Can I combine a large square Head with a non‑standard fixing length or size?

  Not through our customisation service – but we’d love to guide you through our Create service and create a new solution for you.

• Can I combine different product types to reach the 500‑piece minimum order?

  No. The 500‑piece minimum applies per product type. Mixed configurations cannot be combined to meet the threshold.

• Can I request a thread length outside the minimum or maximum values?

  No. These limits reflect manufacturing capability. If your design requires something different, we can help you find the closest viable alternative.

• Can the B50 or S50 Head design itself be modified?

  No, not through our customisation service. The B50/S50 designs (diameter, cropped profile, perforation layout, thickness) are fixed.

• Can the B58 or S58 Head design itself be modified?

  No, not through our customisation service. The B58/S58 designs (diameter, cropped profile, perforation layout, thickness) are fixed.

• Do alternative finishes or coatings change the strength of the fastener?

  No. Alternative finishes and coatings only modify surface‑level properties such as friction, corrosion resistance, or appearance. They do not increase the mechanical strength of the fastener.

• Do I need to specify an end‑form for most bigHead stud applications?

  No. The standard as‑rolled (RL) end‑form is suitable for most applications where straightforward nut installation is required.

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

  Standard collar fixing load limits (FLL) and torque recommendations apply. Weld load limits (WLL) may differ and are available on request.

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

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

• Does changing the thread length affect the performance of the bigHead?

  No. Loadability and material properties remain unchanged. A longer or shorter thread only affects the screw engagement you can achieve during assembly.

• Does custom thread length affect lead time or minimum order quantities?

  Depending on the length selected, it may do. We’ll confirm this when quoting your specification.

• Does end-form customisation affect bigHead product loadability?

  No. ISO 4753 end-forms do not affect weld load limit (WLL), fixing load limit (FLL) or recommended tightening torque values.

• Does using a large round Head change the strength rating of the product?

  Fixing load limits (FLL) remain the same as their standard counterparts. Weld load limits (WLL) and tightening torques may differ. We can provide these on request.

• Does using a large square Head change the strength rating of the product?

  Fixing load limits (FLL) remain the same as their standard counterparts. Weld load limits (WLL) and tightening torques may differ. We can provide these on request.

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

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

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

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

• How do I select the correct screw length for an internally threaded collar?

  For sighted collars: screw engagement ≈ collar length.

  For blind collars: allow clearance (Lu) to avoid screw‑end contact. So Le = L – Lu

  If you’re unsure, see our guide to screw thread length selection, or get in touch.

• How does reverse weld affect overall product length and screw engagement?

  With reverse weld collar, the overall product length is the same as the collar length. This differs from standard collar products, where overall length includes both collar length and Head thickness. Screw engagement is approximately equal to the full collar length.

• 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 are the compatible standard collar lengths for this customisation?

  M4: 10 & 15 mm

  M5 to M8: 10, 15 and 20 mm

  M10 and M12: 15 and 20 mm

• What benefits does a chamfered (CH) end‑form provide?

  CH improves nut lead-in and self-seating, reducing cross-threading during manual or semi-automated assembly. It does not increase the overall stud length.

• What does reverse weld collar customisation involve?

  It reorients the Head position, so that the collar shank passes through the sighted Head. The weld is applied to the flange on the shank side, instead of the Head being welded to the flange end.

• What does the anti-loosening customisation actually change?

  It replaces the standard F1/SF1 nut with a prevailing–torque lock nut, which incorporates a stainless steel locking element that resists rotation under vibration.

• What is the main advantage of a closed blind collar customisation?

  The blind flange collar design prevents resin or polymer ingress during moulding or composite processing, protecting the thread from blockage and reducing rework.

• 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.

• When do I need reverse weld collar customisation?

  Reverse weld collars are useful for applications where:

  • Axial fastening loads or tensile stresses may exceed the weld strength of a standard collar, or
  • You need to present a smooth, uninterrupted Head surface for component seating or moulding shut‑off.
• When should I choose a stainless steel passivation or a Xylan coating?

  Choose passivation when you need improved surface cleanliness or corrosion resistance of 316 stainless steel.

  Choose Xylan when you need a low‑friction, anti‑galling surface or a consistent black aesthetic.

• When should I choose PF or PC pilot points?

  Choose PF (flat pilot shape) when you need enhanced nut lead‑in and reduced cross-threading, such as in automated or repeated manual assembly.

  Choose PC (tapered pilot shape) when you need greater self‑alignment for automated process integration or tighter positional tolerances.

• When should I use a large round Head instead of a standard Head?

  Use a large round Head when you need greater load distribution – typically with thin, flexible, or low‑strength materials where a standard Head may cause localised bending, imprinting, or failure.

• When should I use a large square Head instead of a standard Head?

  Use a large square Head when you need to maximise the load distribution – typically with thin, flexible, or low‑strength materials where a standard Head may cause localised bending, imprinting, or failure.

• Which bigHead products are compatible with reverse weld collar?

  This customisation applies only to sighted internally threaded collar types (F2/SF2) and specific Head types including S20, S23, ST38A, S30, S32 and S38A, with defined thread‑size ranges for each.

• Which thread sizes can be specified with anti-loosening customisation?

  M6, M8, M10, and M12 only. M4 and M5 are unavailable through this route due to our product manufacturing limitations. Contact us to ask about alternative options for M4 or M5 thread sizes.

• Why are flat point (FL) and dog point (SD/LD) not included in ISO 4753 end-form customisation?

  FL is intended for screws that bear against a surface, and SD/LD are intended for screws that locate into holes or slots. Neither supports reliable nut engagement on a stud.

  These forms can look similar to CH, PF and PC. Because of this, we prefer to discuss your requirements before quoting to ensure the correct end-form for your application.

• Why is installation torque higher than with standard nuts?

  Prevailing–torque lock nuts introduce additional friction via a mechanical locking feature, increasing the running torque required during assembly.

• Will coatings affect thread performance or torque settings?

  Potentially, yes. Coatings such as TnT systems or Xylan influence friction levels, so torque values or assembly behaviour may differ from standard finishes. We can advise where torque‑controlled assembly is important.

• Will I need a different screw length for a fastener with a lock nut?

  Possibly. The lock nut design has different height and thread engagement lengths, so you may need a slightly longer screw to ensure proper engagement with the locking feature.

• Will the mechanical performance change compared to standard bigHead F1/SF1 products?

  Yes. The lock nut design uses different geometry, and the associated WLL and tightening torque values are not the same as standard products. We can supply the correct values for your specification on request.