EN 4131:2026

• Abstract:

  This document specifies the characteristics of bolts, normal hexagonal head, coarse tolerance normal shank, medium length thread, in heat resisting nickel base alloy, aluminium IVD coated.; Classification: 1 250 MPa / 425 °C

• Status: Published
• Publication Date: 25-Aug-2026
• ICS: 49.030.20 - Bolts, screws, studs
• Technical Committee: ASD-STAN - Aerospace
• Drafting Committee: ASD-STAN/D 3/S 2 - Fasteners
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 26-Aug-2026
• Completion Date: 26-Aug-2026
• Ref Project: SIST EN 4131:2026 - Aerospace series - Bolt, normal hexagonal head, coarse tolerance normal shank, medium length thread, in heat resisting nickel base alloy, aluminium IVD coated - Classification: 1 250 MPa (at ambient temperature) / 425 °C

• Replaces: EN 4131:2009/AC:2010 - Aerospace series - Bolts, normal hexagonal head, coarse tolerance normal shank, medium length thread, in heat resisting nickel base alloy, aluminium IVD coated - Classification: 1 250 MPa (at ambient temperature) / 425 °C
• Effective Date: 12-Feb-2025
• Replaces: EN 4131:2009 - Aerospace series - Bolts, normal hexagonal head, coarse tolerance normal shank, medium length thread, in heat resisting nickel base alloy, aluminium IVD coated - Classification: 1 250 MPa (at ambient temperature) / 425 °C
• Effective Date: 12-Feb-2025

EN 4131:2026 is a CEN European Standard for aerospace bolts with a normal hexagonal head, coarse tolerance normal shank, medium length thread, made from heat resisting nickel base alloy and aluminium IVD coated. It specifies the bolt characteristics for a classification of 1 250 MPa at ambient temperature and 425 °C, so it is used when the buyer, designer or quality team needs a defined fastener type with fixed dimensions, materials, coating and identification rules.

What does EN 4131:2026 specify?

EN 4131:2026 specifies the characteristics of bolts with a normal hexagonal head, coarse tolerance normal shank, medium length thread, in heat resisting nickel base alloy, aluminium IVD coated. It also ties the product to the classification 1 250 MPa at ambient temperature and 425 °C.

The document is organized into:

• Clause 1 Scope
• Clause 2 Normative references
• Clause 3 Terms and definitions
• Clause 4 Required characteristics
• Clause 5 Designation
• Clause 6 Marking
• Clause 7 Technical specification
• Bibliography

What are the key requirements of EN 4131:2026?

EN 4131:2026 sets the product definition, the dimensional rules, the material options, the coating system, and the identification and qualification rules. In practice, it tells the manufacturer what to make and tells the purchaser what to check on drawings, certificates, and incoming inspection.

Configuration, dimensions and mass

Clause 4.1 says configuration, dimensions and mass shall follow Figure 1 and Tables 1 and 2. The dimensions and tolerances are in millimetres and apply after surface treatment. That matters because final inspection must use the coated condition, not a pre-coat size.

Form, position and thread geometry

Clause 4.2 requires tolerances of form and position in accordance with ISO 7913. The bolt thread form also relies on MJ thread dimensions from ISO 5855-2 and the lead and runout thread rules from ISO 3353-1. This gives a common thread geometry and fit for aerospace use.

Materials

Clause 4.3 allows materials from EN 2952, EN 3219 or TR 3775, all linked to heat resisting nickel base alloy and the 1 250 MPa classification. For users, this means the alloy and supply form are controlled, so the bolt material must match the intended strength and temperature rating.

Surface treatment

Clause 4.4 requires aluminium IVD coating in accordance with EN 6118, type II, or MIL-DTL-83488, type II, with a coating thickness of 7 µm to 20 µm. After aluminium deposit, the bolts need mechanical blasting and then a chromate conversion coating within 24 h, and optional lubrication with cetyl alcohol uses code E. Sharp edges must be broken to 0,1 to 0,4. In practice, coating, timing and lubrication must be controlled as part of manufacture, not added informally later.

Designation and hole options

Clause 5 gives the designation structure, including diameter code, length code, hole code and lubrication code. Table 3 defines hole codes for lockwire, split pin, both, or no hole. This helps procurement specify the exact bolt variant unambiguously on orders and drawings.

Marking

Clause 6 requires marking in accordance with Table 4 and Figure 1. The marking style depends on the diameter code, with one style for 030 and 040 and another for 050 to 200. That matters for traceability and part identification during receiving inspection and in-service control.

Technical specification, approval and qualification

Clause 7 says the technical specification follows EN 2583 with modifications. It also requires the manufacturer to be an approved production organization for aerospace products and to maintain a quality management system, such as EN 9100 or an equivalent. Qualification of bolts is to follow an aerospace standard product qualification procedure, such as EN 9133 or an equivalent, unless the customer and supplier agree otherwise.

What terms does EN 4131:2026 define?

EN 4131:2026 uses these key terms and codes in its designation, marking and technical specification:

• Classification - the strength and temperature rating used for the bolt: 1 250 MPa at ambient temperature and 425 °C.
• Diameter code - the code in Tables 1 and 2 that identifies the nominal bolt diameter.
• Length code - the code in Tables 1 and 2 that identifies the bolt length.
• Hole code - the code in Table 3 that identifies lockwire, split pin, both, or no hole.
• Lubrication code E - the designation for optional lubrication with cetyl alcohol.
• IVD - the aluminium coating process named for this bolt surface treatment.
• QMS - quality management system, the system the manufacturer must maintain.
• MJ threads - the thread system used for these bolts, with limit dimensions taken from ISO 5855-2.

Who uses EN 4131:2026?

EN 4131:2026 is used by aerospace fastener manufacturers, distributors, design offices, buyers, and quality teams. It is also used by laboratories and approval organizations that check qualification, surface treatment, marking and conformance for aerospace bolts.

What changed in EN 4131:2026 from the previous edition?

EN 4131:2026 supersedes EN 4131:2009 + AC:2010. The foreword states these technical changes:

• Clause 2, Normative references, has been updated
• Clause 3, Terms and definitions, has been added
• Table 4 has been updated with new drive code references
• The technical specification changed from ISO 9154 to EN 2583
• Subclause 7.4, Other modified requirement, has been removed

Which standards are used with EN 4131:2026?

EN 4131:2026 refers to these standards and documents:

• EN 2424 - marking of aerospace products
• EN 2583 - the base technical specification, modified by Clause 7
• EN 2952 - bar for forged fasteners in heat resisting alloy NI-PH2601
• EN 3219 - bar and wire for continuous forging or extrusion for fasteners
• EN 6118 - pure aluminium IVD coating for fasteners
• ISO 3353-1 - lead and runout threads for rolled external threads
• ISO 5855-2 - MJ thread limit dimensions for bolts and nuts
• ISO 7913 - tolerances of form and position
• TR 3775 - materials guidance for bolts and pins
• MIL-DTL-83488 - aluminium coating alternative named in the surface treatment clause
• EN 9100 - example of an aerospace quality management system
• EN 9133 - example of an aerospace qualification procedure for standard products

What does the EN 4131:2026 document contain?

EN 4131:2026 contains one figure for the bolt configuration, two dimension-and-mass tables, a hole-code table, a marking table, and an example designation. It also contains the technical specification clause that links the product to manufacturer approval and bolt qualification. For engineering use, the document gives the dimensional and identification data needed for design and procurement, plus the manufacturing and qualification framework needed for conformity control.

SLOVENSKI STANDARD
01-oktober-2026
Aeronavtika - Sorniki, normalna šestroba glava, široka toleranca, srednja navojna
dolžina, iz toplotnoodporne zlitine na nikljevi osnovi, prevlečene z aluminijem IVD -
Klasifikacija: 1250 MPa (pri temperaturi okolice)/425 °C
Aerospace series - Bolt, normal hexagonal head, coarse tolerance normal shank,
medium length thread, in heat resisting nickel base alloy, aluminium IVD coated -
Classification: 1 250 MPa (at ambient temperature) / 425 °C
Luft- und Raumfahrt - Sechskantschraube, mittlere Gewindelänge, aus hochwarmfester
Nickelbasislegierung, Aluminium‑IVD‑beschichtet - Klasse: 1 250 MPa (bei
Raumtemperatur)/425 °C
Série aérospatiale - Vis à tête hexagonale normale, tige normale à tolérance large,
filetage moyen, en alliage résistant à chaud à base de nickel, revêtues aluminium IVD -
Classification: 1 250 MPa (à température ambiante) / 425 °C
Ta slovenski standard je istoveten z: EN 4131:2026
ICS:
49.025.20 Aluminij Aluminium
49.030.20 Sorniki, vijaki, stebelni vijaki Bolts, screws, studs
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 4131
EUROPEAN STANDARD
NORME EUROPÉENNE
August 2026
EUROPÄISCHE NORM
ICS 49.030.20 Supersedes EN 4131:2009
English Version
Aerospace series - Bolt, normal hexagonal head, coarse
tolerance normal shank, medium length thread, in heat
resisting nickel base alloy, aluminium IVD coated -
Classification: 1 250 MPa (at ambient temperature) / 425
°C
Série aérospatiale - Vis à tête hexagonale normale, tige Luft- und Raumfahrt - Sechskantschraube, mittlere
normale à tolérance large, filetage moyen, en alliage Gewindelänge, aus hochwarmfester
résistant à chaud base nickel, revêtue d'aluminium IVD Nickelbasislegierung, Aluminium-IVD-beschichtet -
- Classification : 1 250 MPa (à température Klasse: 1 250 MPa (bei Raumtemperatur)/425 °C
ambiante)/425 °C
This European Standard was approved by CEN on 3 August 2026.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 4131:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 Required characteristics . 5
4.1 Configuration — Dimensions — Mass . 5
4.2 Tolerances of form and position . 5
4.3 Materials . 5
4.4 Surface treatment . 5
5 Designation . 9
6 Marking . 9
7 Technical specification . 9
7.1 General. 9
7.2 Approval of manufacturers . 9
7.3 Qualification of bolts. 10
Bibliography . 11

European foreword
This document (EN 4131:2026) has been prepared by ASD-STAN.
After enquiries and votes carried out in accordance with the rules of this Association, this document has
received the approval of the National Associations and the Official Services of the member countries of
ASD-STAN, prior to its presentation to CEN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by February 2027, and conflicting national standards
shall be withdrawn at the latest by February 2027.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 4131:2009 + AC:2010.
This document includes the following significant technical changes with respect to
EN 4131:2009 + AC:2010:
— Clause 2, “Normative references”, has been updated;
— Clause 3, “Terms and definitions”, added;
— Table 4 (former Table 3) has been updated with new drive code references;
— the technical specification has been changed from ISO 9154 to EN 2583;
— subclause 7.4, “Other modified requirement”, has been removed.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
EN 4
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