ISO/DIS 2974:2025(en)

ISO/TC 22/SC 34

Secretariat: JISC

Date: 2025-10-30

Diesel engines — 60° concave cones for high-pressure fuel injection components

© ISO 2025

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Contents

Foreword iv

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 7

Bibliography 10

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 compared to the previous edition are as follows:

— Language inclusivity was improved.

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Diesel engines — 60° concave cones for high-pressure fuel injection components

This document specifies the dimensional requirements of end-connections for high-pressure fuel injection equipment components, 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).

Details of the pipe connection ends referenced in this document are shown in ISO 13296.

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

For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological 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 dimensioning of the concave cone and the pipe end form

Note 1 to entry: S can be coincident with the intended nominal sealing interface between the concave cone and the pipe end form, or not.

The following figures indicate the requirements for the 60° concave cones at fuel injectors, CR-injectors, fuel injection pumps, high-pressure supply pumps, and rails to allow interchangeability for high- pressure fuel injection pipe assemblies according to ISO 13296:

— Figures 1, 2, 3, and 4 for integral concave cones;

— Figures 5, 6, and 7 for fabricated concave cones.

The 60° concave cone and its relationship to the external thread shall meet the requirements of Figure 1 (integral concave cones) or Figure 5 (fabricated concave cones). However, for integral concave cones, variations at the smaller end of the concave cone as shown in Figure 3 are acceptable.

Dimensions and tolerances are given in Table 1 (integral concave cones) and Table 2 (fabricated concave cones). Unspecified details are left to the manufacturer's choice.

With reference dimension T in Figures 1, 2, 5, and 6, the external thread may be either with or without undercut. However, it shall be possible to screw the GO-gauge for the thread up to the plane specified by dimension T.

Figure 4 and Figure 7 show the assemblies with pipe end connections for the integral and fabricated concave cone types, respectively.

The specification of material and heat treatment shall be made according to the intended use. To ensure tightness of the joint between the connection end of the high-pressure pipe and the concave cone of the mating part of pump, injector, or rail for the initial assembly as well as for repeated assemblies, the necessary plastic deformation shall take place at the sealing face of the high-pressure pipe.

For this purpose, the minimum hardness of the concave cone should be a minimum of 50 HV harder than the maximum hardness of the pipe connection end. However, it shall be proven that the pipe sealing one with its plastic deformation caused by assembly, in combination with the minimum preload, ensures the tightness of the joint for the initial and repeated assembly processes over the product’s useful life.

A 60° concave cone conforming to this document shall be designated by the following elements, in the order given:

a) the term of the 60° concave cone, in accordance with 3.1 or 3.2;

b) a reference to this document (i.e. ISO 2974);

c) the shape, in accordance with Figure 3 (for integral concave cones only);

d) the tube outside diameter, in millimetres;

e) the thread designation, in accordance with ISO 261.

EXAMPLE 1  

A 60° concave cone in accordance with 3.1 (integral concave cone) of shape A, of pipe outside diameter 10 mm, and with an external thread M22 × 1,5 is designated:

Integral concave cone ISO 2974 A 10 – M22 × 1,5

EXAMPLE 2  

A 60° concave cone in accordance with 3.2 (fabricated concave cone), of pipe outside diameter 6,35 mm, and with an external thread M14 × 1,5 is designated:

Fabricated concave cone ISO 2974 6,35 – M14 × 1,5

Dimensions in millimetres,

Surface roughness in micrometres, as defined in ISO 21920-1

^a Highest point of any inserted device. Care shall be taken to ensure that the pipe end does not touch any inserted device after final assembly.

NOTE See Table 1 for dimensions A, E, D, S, and T.

Figure 1 — Integral 60° concave cone without undercut

^a Undercut in accordance with ISO 3508.

NOTE 1 All dimensions and specifications other than the undercut, a, are the same as for the concave cone of Figure 1.

NOTE 2 See Table 1 for dimension T.

Figure 2 — Integral 60° concave cone with undercut

Key

1 reference diameter plane (see dimension S in Table 1)

K (counterbore), size to be agreed between supplier and customer

NOTE See Table 1 for dimensions F1 and F3. Shape C is used for any inserted device (i.e. throttle or edge filter).

Figure 3 — Shapes on integral 60° concave cones according to Figures 1 and 2

Key

1 contact area of connector nut (2) and pipe connection end (3)

2 connector nut

3 connection end of pipe (end form); see NOTE

4 contact area (sealing area) of pipe connection end (3) and concave cone connector (7)

5 chamfer to root of thread [connector nut (2) and connector (7)]

6 engaged thread (recommended design should allow 3x pitch minimum)

7 concave cone (connector)

^a Pipe connection end [pipe connection end bore entrance configuration shall be chosen such that after final assembly, the pipe inside diameter is not reduced (see ISO 13296)].

NOTE For details of pipe connection ends, see ISO 13296.

Figure 4 — Pipe end assembly for integral 60° concave cone (basic relationships)

Table 1 — Integral 60° concave cones

Dimensions in millimetres (see Figure 1, 2, or 3)

Dimensions in millimetres,

Surface roughness in micrometres, as defined in ISO 21920-1

Key

1 chamfer to root of thread

2 concave sealing face

^a Highest point of any inserted device. Care shall be taken to ensure that the pipe end does not touch any inserted device after final assembly.

NOTE See Table 2 for dimensions A, B, C, D, E, S, and T.

Figure 5 — Fabricated 60° concave cone without undercut

^a Undercut in accordance with ISO 3508.

NOTE All dimensions and specifications other than the undercut (see a) are the same as for the concave cone of Figure 5.

Figure 6 — Fabricated 60° concave cone with undercut

Key

1 contact area (sealing area) of pipe connection end (4) and concave cone

2 chamfers to root of thread

3 interface between loading sleeve (6) and connector nut (5)

4 pipe connection end (end form); see a

5 connector nut

6 loading sleeve

7 interface between pipe connection end (4) and loading sleeve (6)

^a Pipe connection end bore entrance configuration shall be so chosen such that after final assembly, the pipe inside diameter is not reduced (see ISO 13296:2024, Figure 5).

Figure 7 — Pipe end assembly for fabricated 60° concave cone (basic relationships)

Table 2 — Fabricated 60° concave cones

Dimensions in millimetres (see Figure 5 or 6)

Bibliography

[1] ISO 7876‑4, Fuel injection equipment — Vocabulary — Part 4: High-pressure pipes and end-connections

[2] ISO 7876‑5, Fuel injection equipment — Vocabulary — Part 5: Common rail fuel injection system

[3] ISO 18418‑1, Gasoline engines — High pressure liquid fuel supply connections — Part 1: 60° concave cone connectors