oSIST prEN 3304:2026

• 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
• Public Enquiry End Date: 09-Sep-2026
• ICS: 49.025.30 - Titanium
• ICS: 49.030.20 - Bolts, screws, studs
• Technical Committee: I13 - Imaginarni 13
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 15-Jul-2026
• Due Date: 02-Dec-2026
• Completion Date: 11-Sep-2026
• Ref Project: prEN 3304 - 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: SIST EN 3304:2001 - 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

oSIST prEN 3304:2026 is the Slovenian publication of prEN 3304, a draft European Standard prepared by ASD-STAN for CEN. It specifies an aerospace screw family with a 100° countersunk reduced head, offset cruciform recess, close tolerance normal shank, short thread, titanium alloy material, anodized finish and MoS2 lubrication, classified for 1 100 MPa at ambient temperature and 315 °C. It is mainly used by manufacturers, procurement teams, and quality or inspection staff who need to specify, make, or check this fastener type.

What does oSIST prEN 3304:2026 specify?

oSIST prEN 3304:2026 specifies the characteristics of one aerospace screw family and the rules used to identify and mark it. The document is organized as a short product specification: geometry and dimensions in Clause 4, designation in Clause 5, marking in Clause 6, technical specification in Clause 7, and oversized-bolt handling in Clause 8.

Section	What it covers
Clause 1	Scope and product family
Clause 2	Normative references that carry requirements
Clause 3	Terms and definitions
Clause 4	Required characteristics
Clause 5	Designation
Clause 6	Marking
Clause 7	Technical specification
Clause 8	Oversized bolts
Bibliography	Related aerospace standards

What are the key requirements of oSIST prEN 3304:2026?

oSIST prEN 3304:2026 combines product geometry, material control, surface treatment, coding, marking and procurement rules. In practice, that means a buyer, designer, or inspector can trace the screw from its drawing form all the way to approval and qualification.

Geometry, dimensions, and mass

Clause 4.1 ties the configuration, dimensions and mass to Figure 1 and Table 1. The dimensions and tolerances apply after anodizing but before lubricating, which matters when inspecting finished parts because the measured size is not taken on the bare part.

Table 1 assigns diameter and length codes, gives the thread form, and provides mass values for screws without holes. For users, this is the basis for selecting the right size and checking that supplied parts match the coded order description.

Tolerances, materials, and surface treatment

Clause 4.2 requires form and position tolerances to follow ISO 7913. Clause 4.3 requires the material to follow TR 3775 for titanium alloy in strength class 1 100 MPa, so the material and strength level are not left to supplier interpretation.

Clause 4.4 requires MoS2 lubrication according to TR 4070, with application according to EN 2491. The surface treatment is part of the product definition, so the lubricant system must match the standard and the finished part must be handled with that finish in mind.

Designation and marking

Clause 5 builds the designation from the hole code, diameter code, length code, drive code and lubricant code. That makes the part number meaningful for purchasing, stock control and drawing callouts, because each code points to a specific feature of the screw.

Clause 6 and Table 4 define marking by diameter code and EN 2424 style. This helps identify the screw after receipt or during assembly, especially where several close variants are used in the same build.

Technical specification and qualification

Clause 7 uses ISO 9152 as the base technical specification, with modifications for this screw family. The manufacturer’s operations must be an approved production organization for aerospace products and must run a quality management system such as EN 9100 or an equivalent accepted system.

Clause 7 also requires product qualification through a procedure such as EN 9133, with the required tests documented unless customer and supplier agree otherwise. This is the part of the standard that matters for acceptance planning, supplier approval and evidence packages.

Oversized bolts

Clause 8 directs oversized bolts to EN 4016. In practice, that tells the user when a non-standard oversize condition should be handled under the dedicated oversized-bolt standard instead of the normal screw specification.

What terms does oSIST prEN 3304:2026 define?

oSIST prEN 3304:2026 uses a small set of product terms and codes that matter in practice.

• Offset cruciform recess - the screw drive recess is a cruciform type with the offset geometry identified by the standard.
• Close tolerance normal shank - the shank is made to tight dimensional tolerances for controlled fit in aerospace assemblies.
• Short thread - the threaded portion is limited to the short-thread configuration defined by the standard’s dimensions.
• Anodized - the screw has an anodized surface treatment, and the dimensional data apply after anodizing.
• MoS2 lubricated - the screw carries a molybdenum disulphide lubricant system to support assembly and reduce friction.
• Classification: 1 100 MPa / 315 °C - the product is identified by a strength class at ambient temperature and a maximum service temperature linked to the surface treatment.

Who uses oSIST prEN 3304:2026?

oSIST prEN 3304:2026 is used by aerospace fastener manufacturers, aircraft and space equipment assemblers, procurement teams, quality managers, and inspection or qualification laboratories. They use it to specify the screw, choose the correct coded variant, check conformity, approve suppliers, and document product qualification for aerospace use.

What changed in oSIST prEN 3304:2026 from the previous edition?

oSIST prEN 3304:2026 supersedes EN 3304:1996. The foreword states these technical changes: Clause 3 was added, Figure 1 was updated, Table 3 drive-code references were changed to ISO 14275 and ISO 14276, and Clause 7 was editorially revised.

Which standards are used with oSIST prEN 3304:2026?

Reference	What it contributes
EN 2424	Marking of aerospace products
EN 2491	Method for applying 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
ISO 9152	Procurement specification for titanium alloy MJ-thread bolts and screws, strength class 1 100 MPa
TR 3775	Materials for bolts and pins
TR 4070	Molybdenum disulphide coatings and commercial products
EN 9100	Example of an aerospace quality management system
EN 9133	Example of a qualification procedure for aerospace standard products
ISO 14275	Drive code reference for offset cruciform, ribbed drives
ISO 14276	Drive code reference for offset cruciform drives

What does the oSIST prEN 3304:2026 document contain?

oSIST prEN 3304:2026 contains a configuration drawing, dimensional tables, mass data, code tables, and a marking table. It also includes technical specification text for manufacturer approval and product qualification, plus a bibliography of related aerospace standards. For a user, that means the document supports design definition, purchasing, incoming inspection, marking checks, and conformity assessment for this screw family.

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
...