prEN 3304

• Abstract:

  This document specifies the characteristics of screws, 100° countersunk reduced head, offset cruciform recess, close tolerance normal shank, short thread, in titanium alloy, anodized, MoS2-lubricated.; Classification: 1 100 MPa1/315 °C2.

• Status: Not Published
• Publication Date: 19-Dec-2027
• ICS: 49.030.20 - Bolts, screws, studs
• Technical Committee: ASD-STAN - Aerospace
• Drafting Committee: ASD-STAN/D 3/S 2 - Fasteners
• Current Stage: 4060 - Closure of enquiry - Enquiry
• Start Date: 17-Sep-2026
• Completion Date: 17-Sep-2026
• Ref Project: oSIST prEN 3304:2026 - Aerospace series - Screw, 100° countersunk reduced head, offset cruciform recess, close tolerance normal shank, short thread, in titanium alloy, anodized, MoS2 lubricated - Classification: 1 100 MPa (at ambient temperature)/315 °C

• Revises: EN 3304:1996 - Aerospace series - Screws, 100° countersunk reduced head, offset cruciform recess, close tolerance normal shank, short thread, in titanium alloy, anodized, MoS2 lubricated - Classification: 1 100 MPa (at ambient temperature)/315 °C
• Effective Date: 20-Jan-2026

Overview

prEN 3304 is a draft European Standard developed by CEN for the aerospace sector, defining the requirements for screws with a 100° countersunk reduced head, offset cruciform recess, close tolerance normal shank, and short thread, manufactured from titanium alloy. These screws are anodized for corrosion resistance and lubricated with molybdenum disulphide (MoS₂) to enhance assembly performance. The classification covers screws with a minimum tensile strength of 1,100 MPa at ambient temperature and suitability for use up to 315°C.

Complying with prEN 3304 supports manufacturers and suppliers in delivering consistent, high-performance fasteners tailored for demanding aerospace applications. This standard supersedes EN 3304:1996 and aligns with the latest industry best practices for titanium fastener components.

Key Topics

• Screw Characteristics: Covers design features including a 100° countersunk, reduced head, offset cruciform recess, close tolerance normal shank, and short thread profile.
• Material Specifications: Focus on titanium alloy, strength class 1,100 MPa, as referenced in ASD-STAN technical reports.
• Surface Treatment: Requires anodizing for enhanced corrosion resistance and application of molybdenum disulphide coatings per aerospace guidelines for lubricity.
• Tolerances and Dimensions: Specifies dimensions and form tolerances in accordance with ISO and EN standards, ensuring interchangeability and high precision.
• Manufacturer and Product Qualification: Mandates manufacturer approval to recognized aerospace quality management systems (e.g. EN 9100) and product qualification according to EN 9133 or equivalent.
• Marking and Designation: Details standardized methods for identification, including hole, diameter, length, drive, and lubricant codes for traceability.

Applications

Aerospace engineering is the primary domain for screws conforming to prEN 3304. The design and classification make these screws ideal for:

• Aircraft Structures: Used in airframe assemblies where close tolerance and weight savings are critical, and operating temperatures may be elevated.
• Engines and Equipment: Suitable for components exposed to mechanical loads and thermal cycling up to 315°C, benefiting from titanium’s strength-to-weight ratio and corrosion resistance.
• Helicopter and Spacecraft Hardware: Where high precision, reliability, and compliance with aerospace fastener standards are essential.
• Repair and Maintenance: Ensures compatibility and consistency in MRO (Maintenance, Repair, and Overhaul) for qualified aerospace parts.

The use of anodized titanium and MoS₂ lubricant addresses both longevity and ease of installation, reducing the risk of galling and simplifying maintenance routines.

Related Standards

To ensure comprehensive compliance and integration with other systems, prEN 3304 references several related standards, including:

• EN 2424: Marking of aerospace products
• EN 2491: Molybdenum disulphide dry lubricant coating methods
• EN 4016: Specifications for oversized bolts in aerospace applications
• ISO 5855-2: MJ thread limit dimensions for bolts and nuts
• ISO 7913: Tolerances of form and position for bolts and screws
• ISO 3353-1: Runout of rolled external threads
• ISO 9152: Procurement specification for titanium alloy bolts, strength class 1,100 MPa
• EN 9100: Aerospace Quality Management Systems
• EN 9133: Qualification procedures for standard aerospace products
• ISO 14275 & ISO 14276: Internal offset cruciform drive specifications

By adhering to prEN 3304 and its referenced standards, organizations can ensure their aerospace fasteners meet rigorous international requirements for performance, quality, and safety.

SLOVENSKI STANDARD
01-september-2026
Aeronavtika - Vijak, 100° ugrezna glava, križna zareza, polno steblo, ozka
toleranca, kratek navoj, iz titanove zlitine, anodizirane, mazane z MoS2 -
Klasifikacija: 1100 MPa (pri temperaturi okolice)/315 °C
Aerospace series - Screw, 100° countersunk reduced head, offset cruciform recess,
close tolerance normal shank, short thread, in titanium alloy, anodized, MoS2 lubricated -
Classification: 1 100 MPa (at ambient temperature)/315 °C
Luft- und Raumfahrt - 100° Senk-Passschraube mit kleinem Kopf, mit Flügelkreuzschlitz
kurzes Gewinde, aus Titanlegierung, anodisiert, MoS2-geschmiert - Klasse: 1 100 MPa
(bei Raumtemperatur)/315 °C
Ta slovenski standard je istoveten z: prEN 3304
ICS:
49.025.30 Titan Titanium
49.030.20 Sorniki, vijaki, stebelni vijaki Bolts, screws, studs
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2026
ICS 49.030.20 Will supersede EN 3304:1996
English Version
Aerospace series - Screw, 100° countersunk reduced head,
offset cruciform recess, close tolerance normal shank,
short thread, in titanium alloy, anodized, MoS2 lubricated -
Classification: 1 100 MPa (at ambient temperature)/315
°C
Luft- und Raumfahrt - 100° Senk-Passschraube mit
kleinem Kopf, mit Flügelkreuzschlitz kurzes Gewinde,
aus Titanlegierung, anodisiert, MoS2-geschmiert -
Klasse: 1 100 MPa (bei Raumtemperatur)/315 °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 3304:2026 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 . 4
4.1 Configuration – Dimensions – Mass. 4
4.2 Tolerance of form and position . 5
4.3 Materials . 5
4.4 Surface treatment . 5
5 Designation . 8
6 Marking . 8
7 Technical specification . 8
7.1 General. 8
7.2 Approval of manufacturers . 9
7.3 Qualification of products . 9
7.4 Requirements deleted . 9
8 Oversized bolts . 9
Bibliography . 10

European foreword
This document (prEN 3304:2026) 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 3304:1996.
— Clause 3, “Terms and Definitions”, added;
— Figure 1 updated;
— Table 3, “Drive codes”, references changed to ISO 14275 and ISO 14276;
— Clause 7, “Technical specification”, editorially revised.
1 Scope
This document specifies the characteristics of screws, 100° countersunk reduced head, offset cruciform
recess, close tolerance nor
...