ISO 2974:2026

International
Standard
ISO 2974
Tenth edition
Diesel engines — 60° concave cones
2026-10
for high-pressure fuel injection
components
Moteurs diesels — Raccords finaux à cône concave de 60° pour
lignes d'injection de carburants haute pression
Reference number
© ISO 2026
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Requirements . 2
4.1 Dimensions and tolerances . .2
4.2 Materials .2
5 Designation . 2
6 Figures and tables . 3
6.1 Integral 60° concave cone . .3
6.2 Fabricated 60° concave cone .6
Bibliography .10

iii
Foreword
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This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 34,
Propulsion, powertrain and powertrain fluids.
This tenth edition cancels and replaces the ninth edition (ISO 2974:2018), which has been technically
revised.
The main changes are as follows:
— language inclusivity was improved;
— new thread option M16 × 1,0 in Table 1;
— updated reference standard ISO 21920-1 for roughness indication.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
To comply with recent exhaust gas regulations and fuel consumption regulations for internal combustion
engines, the fuel injection pressure of automobile diesel engines is generally 2 000 bar or more. Fuel injection
systems operating at pressures of approximately 2 700 bar are also being introduced to the market.
Since this fuel injection pressure is extremely high, the dimensions and specifications of the 60° concave
cones for high pressure fuel connections are standardized. This is to prevent fuel leaking from the joint or
other failures.
v
International Standard ISO 2974:2026(en)
Diesel engines — 60° concave cones for high-pressure fuel
injection components
1 Scope
This document specifies the dimensional requirements of end-connections for high-pressure fuel injection
equipment components, including fuel injectors, CR injectors, common rails, distribution blocks, injection
pumps and high-pressure supply pumps used on diesel (compression-ignition) engines.
It is applicable to externally threaded 60° concave cones (see Figures 1, 2, 5, and 6) and intended for use
with high-pressure fuel injection pipe assemblies with tube outside diameters of:
— up to and including 12 mm for integral concave cones (see Table 1); and
— up to and including 9 mm for fabricated concave cones (see Table 2).
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 261, ISO general purpose metric screw threads — General plan
ISO 21920-1, Geometrical product specifications (GPS) — Surface texture: Profile — Part 1: Indication of surface
texture
ISO 3508, Thread run-outs for fasteners with thread in accordance with ISO 261 and ISO 262
ISO 13296, Diesel engines — High-pressure fuel injection pipe assemblies — General requirements and
dimensions
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
integral concave cone
concave cone where the sealing cone and the thread are connected in the same part
Note 1 to entry: See Figures 1 and 2.
3.2
fabricated concave cone
concave cone where the sealing cone and the thread are separate parts prior to joining, e.g. by welding
Note 1 to entry: See Figures 5 and 6.

3.3
reference diameter
S
baseline for
...