prEN 3377

• Status: Not Published
• Publication Date: 14-Sep-2027
• ICS: 49.030.30 - Nuts
• Technical Committee: ASD-STAN - Aerospace
• Drafting Committee: ASD-STAN/D 3/S 2 - Fasteners
• Current Stage: 4060 - Closure of enquiry - Enquiry
• Start Date: 16-Jul-2026
• Completion Date: 16-Jul-2026
• Ref Project: oSIST prEN 3377:2026 - Aerospace series - Nuts, hexagonal, self-locking, in heat resisting steel FE-PA92HT (A286) - Classification : 1 100 MPa (at ambient temperature) / 425 °C

• Revises: EN 3377:1996 - Aerospace series - Nuts, hexagonal, self-locking, in heat resisting steel FE-PA92HT (A 286) - Classification: 1 100 MPa (at ambient temperature)/425°C
• Effective Date: 20-Jan-2026

prEN 3377 is a CEN draft European Standard for aerospace self-locking hexagonal nuts made from heat resisting steel FE-PA92HT (A286). It specifies the nuts’ classification at 1 100 MPa at ambient temperature and 425 °C, and covers the dimensions, material options, marking, and technical specification used for aerospace applications.

What does prEN 3377 specify?

prEN 3377 specifies the characteristics of self-locking hexagonal nuts in FE-PA92HT for aerospace applications. The document is organized into Scope, Normative references, Terms and definitions, Required characteristics, Designation, Marking, Technical specification, and a Bibliography.

The scope sets the product type and the performance class: self-locking hexagonal nuts for aerospace use, classified as 1 100 MPa / 425 °C. In practice, that tells a buyer or engineer which nut family and temperature class the standard is intended to cover.

What are the key requirements of prEN 3377?

prEN 3377 ties the nut’s geometry, material, marking, and qualification rules to specific clauses and referenced standards. For selection and inspection, the most important points are the size table, the permitted material sources, the thread system, and the approval and qualification route.

• Clause 4.1 requires the configuration, dimensions, tolerances, and mass to follow Figure 1 and Table 1, with dimensions in millimetres. This is the main control for interchangeability and weight.
• Clause 4.2 limits materials to EN 2399, EN 3638, EN 3639, or TR 3791, and for MJ3 and MJ4 to SAE AMS5525 at the manufacturer’s discretion. This matters because the nut must suit the heat-resisting aerospace service environment.
• Clause 4.1 also points to ISO 7995 for dimensions and ISO 5855-2 for MJ thread limit dimensions. That gives the thread fit and envelope used when checking compatibility with bolts and sockets.
• Figure 1 defines the nut configuration, including the self-locking zone, permitted entry forms, edge treatment, and marking areas. In practice, this tells production and inspection what shape features are controlled and which details remain the manufacturer’s option.
• Table 1 gives the thread codes and sizes from MJ3 to MJ12, together with approximate mass per 1 000 pieces. This is the part most often used for part selection, cataloguing, and procurement.
• Clause 5 gives the designation format, for example NUT EN3377-050, where the code identifies the thread size. This is the ordering and documentation reference.
• Clause 6 requires marking in accordance with EN 2424 and Table 2, with style N for diameter codes 030 and 040, and style C for 050 to 120. That supports traceability on the part.
• Clause 7 makes the technical specification follow EN 3152, with modifications. It also requires an approved aerospace production organization and a quality management system such as EN 9100 or an equivalent system, plus a documented qualification procedure such as EN 9133 or an equivalent procedure unless customer and supplier agree otherwise.

What terms does prEN 3377 define?

• Self-locking - The nut is designed to resist loosening, and the document uses controlled out-of-round forming in the self-locking zone to achieve that function.
• FE-PA92HT (A286) - This is the heat resisting steel named for the nut material family in the standard.
• MJ threads - This is the aerospace metric thread form used for the nuts, with limit dimensions taken from ISO 5855-2.
• Classification 1 100 MPa / 425 °C - This identifies the strength class at ambient temperature and the maximum temperature level associated with the nut.
• Approved production organization - A manufacturer whose aerospace production operations are approved and who maintains an accepted quality management system.
• Qualification of products - The documented procedure used to qualify the nuts by the specified tests, unless a customer-supplier agreement says otherwise.

Who uses prEN 3377?

prEN 3377 is used by aerospace fastener manufacturers, suppliers, design engineers, quality teams, and buyers. They use it to specify, make, inspect, mark, approve, and qualify self-locking hexagonal nuts for aerospace assemblies.

It is especially relevant when a part must be traced to a defined thread code, material route, and aerospace quality system. That makes it useful in procurement, incoming inspection, production control, and product qualification.

What changed in prEN 3377 from the previous edition?

prEN 3377 will supersede EN 3377:1996. The foreword names three significant changes: Clause 3, “Terms and definitions”, was added; TR 3791 and SAE AMS5525 were added in 4.2; and Clause 7 was editorially revised.

Which standards are used with prEN 3377?

Standard	What it contributes
EN 2399	One of the permitted material references for the nuts
EN 2424	Marking of aerospace products
EN 3152	Base technical specification, with modifications in this document
EN 3638	One of the permitted material references
EN 3639	One of the permitted material references
ISO 5855-2	MJ thread limit dimensions for bolts and nuts
ISO 7995	Dimensions for hexagonal self-locking nuts with MJ threads
TR 3791	Material guidance for self-locking nuts and related inserts up to 425 °C
SAE AMS5525	Permitted material reference for MJ3 and MJ4 at manufacturer’s discretion
EN 9100	Example of an accepted aerospace quality management system
EN 9133	Example of an accepted aerospace qualification procedure

What does the prEN 3377 document contain?

The document contains a configuration figure, a dimensions and mass table, a marking table, and clauses on designation and technical specification. It also includes the material requirements and the approval and qualification framework used for aerospace production.

For practical use, the document gives the nut geometry, the size codes, the permitted material routes, and the marking method together in one place. That lets engineers, purchasers, and quality teams check fit, material suitability, traceability, and product approval against the same standard.

SLOVENSKI STANDARD
01-julij-2026
Aeronavtika - Matice, šestrobe, samozapiralne, iz toplotnoodpornega jekla FE-
PA92HT (A286) - Klasifikacija: 1100 MPa (pri temperaturi okolice)/425 °C
Aerospace series - Nuts, hexagonal, self-locking, in heat resisting steel FE-PA92HT
(A286) - Classification : 1 100 MPa (at ambient temperature) / 425 °C
Luft- und Raumfahrt - Sechskantmutter, selbstsichernd, aus hochwarmfesten Stahl FE-
PA92HT (A286) - Klasse: 1 100 MPa (bei Raumtemperatur)/425 °C
Ta slovenski standard je istoveten z: prEN 3377
ICS:
49.025.10 Jekla Steels
49.030.30 Matice Nuts
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
April 2026
ICS 49.030.30 Will supersede EN 3377:1996
English Version
Aerospace series - Nuts, hexagonal, self-locking, in heat
resisting steel FE-PA92HT (A286) - Classification : 1 100
MPa (at ambient temperature) / 425 °C
Luft- und Raumfahrt ¿ Sechskantmutter,
selbstsichernd, aus hochwarmfesten Stahl FE-PA92HT
(A286) ¿ Klasse: 1 100 MPa (bei
Raumtemperatur)/425 °C
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee ASD-
STAN.
If this draft becomes a European Standard, 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.

This draft European Standard was established by CEN 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.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

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. prEN 3377:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 5
4 Required characteristics . 5
4.1 Configuration – Dimensions – Tolerances – Mass . 5
4.2 Materials . 5
5 Designation . 8
6 Marking . 8
7 Technical specification . 8
7.1 General. 8
7.2 Approval of manufacturers . 8
7.3 Qualification of products . 8
Bibliography . 9

European foreword
This document (prEN 3377:2026) 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 document is currently submitted to the CEN Enquiry.
This document will supersede EN 3377:1996.
— Clause 3, “Terms and definitions”, added;
— 4.2, “Materials”, standards TR 3791 and SAE AMS5525 added;
— Clause 7, “Technical specification”, editorially revised.
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