---
title: "Large round Head"
id: "9336"
type: "guides"
slug: "large-round-head"
published_at: "2026-05-07T15:37:44+00:00"
modified_at: "2026-05-22T09:39:51+00:00"
url: "https://bighead.co.uk/the-techub/guides/large-round-head/"
markdown_url: "https://bighead.co.uk/the-techub/guides/large-round-head.md"
excerpt: "Guidance on specifying large round Head customisation for bigHead fasteners, covering compatibility, load‑spreading benefits and key design considerations."
taxonomy_guide_category:
  - "Customisation guides"
---

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Customisation guides

# Large round Head

[Back to guides](../)

## Key takeaways

- You can request large round Head customisation for a range of standard bigHead studs, collars, nuts, pins, and nails.
- Large round Heads provide ~2× the load‑spreading area of standard Head designs.
- They provide extra load-spreading, reducing stresses and helping prevent material failure in thin or lower-stiffness substrates.
- Fixing lengths and thread sizes are the same as their equivalent standard products.
- Perforation patterns and Head designs are fixed (50 mm cropped circle, 1.2 mm thickness).
- Installation strength depends on adhesive or embedment design.
- FLL values match the standard bigHead counterparts, but WLL and tightening torque recommendations may differ (available on request).
- Identified by product code **B50** (blind) or **S50** (sighted).

![Top view of a bigHead B50 Head showing Ø 50 mm outer diameter, 48 mm across flats and perforation hole arrangement](https://bighead.co.uk/wp-content/uploads/2026/05/Large-Round-Head-dimensions-1.jpg)

Key dimensions for bigHead with large round Head customisation

![Isometric section view of a bigHead F2 type fastener with B50 large round Head customisation showing screw entry direction](https://bighead.co.uk/wp-content/uploads/2026/05/Large-Round-Head-F2B50-section.jpg)

Section view of F2/B50 bigHead large round Head customisation (SF2/B50 is similar)​

![Isometric section view of a bigHead F2 type fastener with S50 large round Head customisation showing screw pass-through direction](https://bighead.co.uk/wp-content/uploads/2026/05/Large-Round-Head-F2S50-section.jpg)

Section view of F2/S50 bigHead large round Head customisation (SF2/S50 is similar)

## Customisation scope for large round Head

This customisation replaces the standard Head component with a large round Head component. It can be blind or sighted.

### Products compatible with blind large round Head (B50)

Standard lengths for externally threaded studs (M1/SM1), by thread size:

- M4 → 12, 16, 20 and 25 mm
- M5 → 12, 16, 20, 25, 30 and 40 mm
- M6 and M8 → 12, 16, 20, 25, 30, 40, 50 and 75 mm
- M10 → 20, 25, 30 and 40 mm

Blind internally threaded collars (F2/SF2), standard collar lengths by thread size:

- M4 → 10 and 15 mm
- M5 – M10 → 10, 15 and 20 mm
- M12 → 15 and 20 mm

Unthreaded pin (M4) – carbon steel and bright zinc plate only, standard pin lengths:

- 5 mm diameter pin → 12, 20, 25, 30, and 40 mm

Nail (SM5) – 316 stainless steel only, standard nail lengths:

- 3 mm diameter nail → 30, 50, 75, 100 and 125 mm

### Products compatible with sighted large round Head (S50)

Sighted internally threaded collars (F2/SF2), standard collar lengths by thread size:

- M4 → 5, 10 and 15 mm
- M5 and M6 → 5, 10, 15 and 20 mm
- M8 and M10 → 10, 15 and 20 mm
- M12 → 15 and 20 mm

Sighted internally threaded nuts (F1/ SF1), standard nut sizes:

- M4, M5, M6, M8, M10 and M12

## What's outside the scope of large round Head customisation

Non-applicable product types:

- 45 degree loop (M7/SM7)
- 90 degree loop (M8/SM8)
- Cable tyrap

Complex requests are out-of-scope due to manufacturing constraints. Examples:

- Combining a large round Head with a non-standard fixing length
- Modifying the B50/S50 Head geometry or perforation pattern

If you have an out-of-scope request, we can work with you to create a solution –[get in touch](https://bighead.co.uk/?post_type=guides&p=9329&preview=true#contact-form)
.

## Design and performance considerations for large round Head

The large round Head has about twice the surface area of standard B38A/S38A bigHead products:

- B38A = ~880 mm²
- B50 = ~1770 mm²

The large round Head footprint (A) is ~50 mm in diameter. The two cropped sides are 48 mm apart (B).

### Loadability

- Fixing load limit (FLL) values match the equivalent standard products.
- Weld load limits (WLL) and tightening torque recommendations may differ to standard products. We can provide this information on request.

### Embedding and surface bonding performance

Embedding and surface bonding performance varies depending on the embedment design or adhesive. Because of this, we can’t provide simple installation strength comparisons between our standard products and large round Head designs.

If you need performance data for a large round Head customisation, [get in touch](https://bighead.co.uk/?post_type=guides&p=9329&preview=true#contact-form)
. We’ll help you explore the best options for your application.

## Specification examples for large round Head customisation

### Example 1: Carbon steel, bright zinc plate (BZP) finish

To specify an externally threaded stud, M6 × 40 mm, on a B50 Head:

- Product type: M1
- Large round Head customisation: B50
- Thread diameter: M6
- Customised thread length (L): 40 mm
- Stud material suffix: HT (carbon steel, heat treated)

**→ M1/B50 M6 × 40 HT**

### Example 2: 316 stainless steel

To specify an internally threaded nut, M10, on a sighted S50 Head:

- Material prefix: S (316 stainless steel)
- Product type: F1
- Large round Head customisation: S50
- Thread diameter: M10

**→ SF1/S50 M10**

### Example 3: Out of scope

A request for M10 × 30 mm collar (F2) on a blind B50 head is not possible through our customisation service as 30mm is not a standard product size.

Instead, we can create a solution for you through our [Create service](https://bighead.co.uk/bespoke/create/)
.

# Next steps

## Requesting a large round Head customisation

Contact us with your required product code to request a quote or confirm suitability.

If needed, we can help you define whether a large round Head is suitable for your application.

**Contact:**  
 Email: [sales@bigHead.co.uk](mailto:sales@bigHead.co.uk)
  
 Tel: +44 (0) 1202 574601

**Sales availability:**  
 Mon–Thu: 07:30–16:15 (UK)  
 Fri: 07:30–12:15 (UK)

[Get in touch](#contact-form)

## FAQs

- 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.
- 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.
- 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.
- 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](https://bighead.co.uk/bespoke/create/) and create a new solution for you.
- 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.

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