Customisation scope for ISO 4753 end-forms

This customisation modifies the geometry at the end of an externally threaded stud (M1/SM1), according to ISO 4753 standardised forms.

Compatible Head types, by thread size

• B15: M4 – M6
• B20, B23: M4 – M8
• B30, B32, B38A, T38A: M4 – M10

Standard stud lengths, 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

Compatible end-forms

Standard bigHead externally threaded studs come with an as-rolled (RL) end-form.

Three alternative ISO 4753 end-forms are also compatible with bigHead customisation. These options can provide additional alignment, lead‑in, or assembly support:

• Chamfered end (CH)
• Pilot point, flat (PF)
• Pilot point with truncated cone (PC)

Chamfered end (CH)​

Pilot point, flat (PF)

Pilot point with truncated cone (PC)

Incompatible end-forms

Flat point (FL)

FL end-forms are not suitable for bigHead studs that receive a nut.

FL creates a broad, flat bearing surface for set screws and grub screws, where the tip must press against a surface without digging in. It does not support nut engagement and removes the lead-in needed for reliable nut running.

Although FL looks similar to CH, they serve different functions. CH forms a tapered lead-in that helps the nut self-seat, reducing cross-threading and improving manual or automated nut running.

Dog points (SD/LD)

In ISO 4753, dog points are unthreaded cylindrical extensions designed to locate into holes, slots or grooves.

These forms are not compatible with threaded fasteners or bigHead studs intended to receive a nut, especially in automated assembly.

For help, see our guide to selecting end-forms, or get in touch.

What's outside the scope of ISO 4753 end-form customisation

Some requests are not compatible with ISO 4753 end-form customisation. Examples:

• Combining ISO 4753 end-forms with other customisations
• Flat point (FL) and dog point (SD/LD) end-forms

If you have an out-of-scope request, we can work with you to create a solution – get in touch.

Design and performance considerations for ISO 4753 end-forms

The dimensional impact of this customisation varies according to your chosen end-form.

Effect on usable thread length (Le)

CH, PF and PC end-forms all create a short length of incomplete thread (Lu), reducing usable thread length (Le).

Lu varies by thread size and is approximate due to geometry tolerances.

Incomplete thread length (Lu) values, by thread size:

• M4: ≤1.4 mm
• M5: ≤1.6 mm
• M6: ≤2.0 mm
• M8: ≤2.5 mm
• M10: ≤3.0 mm

Le min ≈ L – Lu

Examples:

• For M6 × 20 mm stud, Le min ≈ 18 mm (20 – 2)
• For M8 × 50 mm stud, Le min ≈ 47.5 mm (50 – 2.5)

Effect on overall stud length

• CH end-forms: No change to overall stud length or product length. The chamfer is formed within the existing thread length envelope.
• PF and PC end-forms: Increase overall stud length due to the added pilot feature.

Additional length (Lz) for PF and PC end-forms, by thread size:

• M4: 2.0 mm
• M5: 2.5 mm
• M6: 3.0 mm
• M8: 4.0 mm
• M10: 5.0 mm

Overall bigHead stud product length:

Overall length = L + Lz + L1 (shoulder) + 1.2 (Head)

Where 1.2 mm is the Head thickness for standard bigHead products.

Examples:

• For M6 × 20, overall length = 25.4 mm (20 + 3 + 1.2 + 1.2)
• For M8 × 50, overall length = 56.7 mm (50 + 4 + 1.5 + 1.2)

Effects on performance

ISO 4753 end-form customisation does not affect:

• Weld load limit (WLL)
• Fixing load limit (FLL)
• Recommended tightening torque values

These values carry over from standard M1/SM1 products.

Specification examples for ISO 4753 end-form customisation

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

To specify an ISO 4753 chamfered end (CH) on an M6 × 20 mm stud with B20 Head:

• Product type: M1/B20
• Thread × nominal length: M6 × 20
• Customisation suffix: CF

→ M1/B20 M6 × 20 CF

• Usable thread length (Le): ~18 mm
• Overall product length: 22.4 mm

Example 2: 316 stainless steel

To specify an ISO 4753 pilot point, flat (PF) on an M8 × 50 mm stud with B38A Head:

• Material prefix: S (316 stainless steel)
• Product type: M1/B38A
• Thread × nominal length: M8 × 50
• Customisation suffix: PF

→ SM1/B38A M8 × 50 PF

• Usable thread length (Le): ~47.5 mm
• Overall product length: 56.7 mm

Example 3: Carbon steel, bright zinc plate (BZP) finish

To specify an ISO 4753 truncated cone pilot point (PC) on an M5 x 30 mm stud with T38A Head:

• Product type: M1/T38A
• Thread × nominal length: M5 x 30
• Customisation suffix: PC

→ M1/T38A M5 × 30 PC

• Usable thread length (Le): ~28.4 mm
• Overall product length: 34.9 mm

Example 4: Out of scope

An ISO 4753 long dog point (LD) end-form on an M8 × 20 mm stud with a B23 head is not possible. LD end‑forms are not suitable for bigHead stud fixings.