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: 15-Nov-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

prEN 3304 is a draft European Standard from CEN for aerospace screws with a 100° countersunk reduced head, offset cruciform recess, close tolerance normal shank and short thread, made in titanium alloy, anodized and lubricated with MoS2 (molybdenum disulphide). It specifies the characteristics of screws classified as 1 100 MPa at ambient temperature / 315 °C. In practice, it is the document manufacturers, buyers and approval bodies use to define the screw design, material, surface treatment, marking and qualification route.

What does prEN 3304 specify?

prEN 3304 specifies the characteristics of these aerospace screws and organizes them into clauses for scope, references, definitions, required characteristics, designation, marking, technical specification and oversized bolts. The document is structured so that the product definition, the ordering code and the qualification rules can be used together.

Clause 4 is the technical core. It links the screw’s configuration, dimensions and mass to Figure 1 and Table 1, then sets rules for form and position tolerances, materials and surface treatment. Clause 5 defines how the screw is designated for ordering, and Clause 6 defines the marking on the product.

What are the key requirements of prEN 3304?

Configuration, dimensions and mass

Clause 4.1 ties the screw geometry to Figure 1 and Table 1. It also states that dimensions and tolerances are in millimetres and apply after anodizing but before lubricating. For users, this means measurements and acceptance checks have to be made against the finished, anodized part, not the raw machined blank.

Form, position and material

Clause 4.2 requires tolerances of form and position to follow ISO 7913. Clause 4.3 requires materials in accordance with TR 3775, using titanium alloy in strength class 1 100 MPa. In practice, the screw is not just a geometry item - the material class and geometric tolerances are part of the purchase specification.

Surface treatment and lubrication

Clause 4.4 requires lubrication in accordance with TR 4070 and application in accordance with EN 2491. The document also links the maximum service temperature to the surface treatment. For procurement and inspection, this means the coating and lubricant are controlled parts of the product definition, not optional extras.

Designation for ordering

Clause 5 defines a coded designation built from the hole code, diameter code, length code, drive code and lubricant code. Table 2 gives the hole codes and Table 3 gives the drive codes. This matters because the designation is the compact way to state exactly which screw is being ordered or recorded in controlled documents.

Marking

Clause 6 links marking to EN 2424 and to the screw size. The marking rules help traceability and make it easier to identify the approved product after delivery, storage and assembly.

Technical specification, approval and qualification

Clause 7 says the technical specification follows ISO 9152, with modifications. It also requires the manufacturer to be an approved production organization for aerospace products and to operate a quality management system such as EN 9100 or an equivalent aerospace accepted and established system. Product qualification follows an aerospace qualification procedure such as EN 9133 or an equivalent procedure, with the specified tests documented unless buyer and supplier agree otherwise.

Oversized bolts

Clause 8 routes oversized bolts to EN 4016. If an application needs an oversized bolt variant, the user is directed to the separate oversized-bolt specification rather than adapting the standard screw informally.

Who uses prEN 3304?

prEN 3304 is used by aerospace fastener manufacturers, source inspectors, purchasing teams, design engineers and quality managers. It is also used by qualification and approval organizations that need a common basis for product testing, marking and acceptance. The main tasks are specifying the screw, checking conformity, qualifying a manufacturer and documenting procurement requirements.

What changed in prEN 3304 from the previous edition?

prEN 3304 will supersede EN 3304:1996. The foreword states these significant technical changes:

• Clause 3, Terms and Definitions, was added.
• Figure 1 was updated.
• Table 3 references were changed to ISO 14275 and ISO 14276.
• Clause 7, Technical specification, was revised editorially.

Which standards are used with prEN 3304?

• EN 2424 - marking of aerospace products.
• EN 2491 - coating methods for molybdenum disulphide dry lubricants.
• EN 4016 - oversized bolts.
• 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 for aerospace bolts and screws.
• ISO 9152 - procurement specification for titanium alloy bolts and screws in strength class 1 100 MPa.
• TR 3775 - materials for aerospace bolts and pins.
• TR 4070 - list of commercial products for molybdenum disulphide coatings.
• EN 9100 and EN 9133 - cited as examples of acceptable quality management and qualification approaches.

What does the prEN 3304 document contain?

prEN 3304 contains a configuration figure, a size-and-mass table, code tables for hole and drive options, and a marking table. It also gives the designation system and the technical specification rules used for approval and qualification. For users, the document is mainly a combined design, ordering, inspection and qualification reference for this screw type.

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
...