SIST 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
• Public Enquiry End Date: 22-Oct-2025
• Publication Date: 09-Sep-2026
• ICS: 49.025.20 - Aluminium
• ICS: 49.030.20 - Bolts, screws, studs
• Technical Committee: I13 - Imaginarni 13
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 04-Sep-2026
• Due Date: 09-Nov-2026
• Completion Date: 10-Sep-2026
• Ref Project: 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

• Revises: SIST 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
• Revises: SIST 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: 1250 MPa (at ambient temperature) / 425 °C
• Effective Date: 12-Feb-2025

SIST EN 4131:2026 is the Slovenian adoption of EN 4131:2026 from SIST and CEN. It specifies aerospace bolts with a normal hexagonal head, coarse tolerance normal shank, medium length thread, made from a heat resisting nickel base alloy and aluminium IVD coated. The bolt classification is 1 250 MPa at ambient temperature / 425 °C, so the document is intended for aerospace design, procurement, manufacture, marking and qualification of this fastener type.

What does SIST EN 4131:2026 specify?

SIST EN 4131:2026 specifies the characteristics of one bolt family for aerospace use. It covers the bolt configuration, dimensions, mass, tolerances, material, surface treatment, designation, marking and technical specification.

The document is arranged in clauses 1 to 7, followed by a bibliography. Clause 4 contains the required characteristics, with subclauses for configuration, tolerances, materials and surface treatment. Clause 5 gives the designation system, Clause 6 gives marking, and Clause 7 gives the technical specification, including manufacturer approval and qualification.

What are the key requirements of SIST EN 4131:2026?

• Clause 4.1 ties the bolt geometry, dimensions and mass to Figure 1 and Tables 1 and 2. The dimensions and tolerances are in millimetres and apply after surface treatment. In practice, this means the finished, coated bolt is the reference for checking size.

• Clause 4.2 requires form and position tolerances to follow ISO 7913. That matters because the bolt must fit and function correctly in aerospace assemblies, not only meet nominal thread size.

• Clause 4.3 limits the material options to EN 2952, EN 3219 or TR 3775 for the heat resisting nickel base alloy classification 1 250 MPa. This gives the buyer and manufacturer a defined material route for procurement and certification.

• Clause 4.4 specifies the aluminium IVD coating by reference to EN 6118 type II or MIL-DTL-83488 type II, with coating thickness 7 µm to 20 µm. It also requires mechanical blasting, then chromate conversion coating within 24 h, and allows optional lubrication with cetyl alcohol, code E. For users, this is the key surface system that controls corrosion performance and the temperature class.

• Clause 4.4 also requires sharp edges to be broken within the stated range and leaves unspecified form details to manufacturer discretion. That means drawings and shop practice still need to control the remaining details consistently.

• Clause 5 sets the designation structure using hole code, diameter code, length code and lubrication code. The hole codes in Table 3 identify lockwire, split pin, both, or no hole, so purchase orders can specify the exact fastening feature needed.

• Clause 6 defines marking by diameter code and EN 2424 style. Marking supports traceability in production, stock control and inspection.

• Clause 7 bases the technical specification on EN 2583, with stated modifications. It requires an approved production organization and a quality management system such as EN 9100 or an equivalent aerospace accepted and established system, and it calls for qualification of bolts by a procedure such as EN 9133 or an equivalent approved procedure. In practice, suppliers must be able to prove both process control and product qualification.

What terms does SIST EN 4131:2026 define?

• Classification - the bolt class stated in the title, combining 1 250 MPa at ambient temperature with 425 °C for the temperature capability.

• Hole code - the designation element that identifies whether the bolt is for lockwire, split pin, both, or no hole.

• Diameter code - the code used in the designation and marking to identify the bolt size.

• Length code - the code used in the designation and marking to identify the bolt length.

• Lubrication code E - the optional designation code for cetyl alcohol lubrication.

• Approved production organization - a manufacturer whose operations are approved for aerospace products and whose quality management system is maintained.

Who uses SIST EN 4131:2026?

SIST EN 4131:2026 is used by aerospace fastener manufacturers, procurement teams, quality managers, inspectors and design engineers. They use it to specify, make, mark, buy and verify bolts with a defined head form, material, coating and qualification route. It is also relevant to qualification laboratories and auditors who check supplier capability and product conformance.

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

SIST EN 4131:2026 supersedes EN 4131:2009 + AC:2010. The foreword states these changes from the previous edition: Clause 2 was updated, Clause 3 was added, Table 4 was updated with new drive code references, the technical specification was changed from ISO 9154 to EN 2583, and subclause 7.4 was removed.

Which standards are used with SIST EN 4131:2026?

• EN 2424 - provides the marking style for aerospace products.
• EN 2583 - provides the technical specification used in Clause 7.
• EN 2952 - provides one permitted material form for the nickel base alloy.
• EN 3219 - provides another permitted material form for the nickel base alloy.
• EN 6118 - defines pure aluminium IVD coating for fasteners.
• ISO 3353-1 - covers lead and runout threads for rolled external threads.
• ISO 5855-2 - gives MJ thread limit dimensions for bolts and nuts.
• ISO 7913 - gives tolerances of form and position for metric bolts and screws.
• TR 3775 - gives materials guidance for aerospace bolts and pins.
• MIL-DTL-83488 - provides the alternative aluminium coating requirement named in Clause 4.4.
• EN 9100 - is cited as an example of the quality management system expected from manufacturers.
• EN 9133 - is cited as an example qualification procedure for aerospace standard products.

What does the SIST EN 4131:2026 document contain?

SIST EN 4131:2026 contains Figure 1 for the bolt configuration, Tables 1 and 2 for dimensions and mass, Table 3 for hole codes, and Table 4 for marking. It also includes a designation example and the technical requirements for material, coating, marking, manufacturer approval and qualification. These parts are the practical basis for drawing control, supplier specification, inspection and product identification.

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
...