ISO 2974 - Diesel engines — 60° female 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, used on diesel (compression-ignition) engines. It is applicable to externally threaded 60° female 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 female cones (see Table 1); and 

— up to and including 9 mm for fabricated female cones (see Table 2). 

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

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 1302, Geometrical Product Specifications (GPS) — Indication of surface texture in technical product documentation 

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 terminological databases for use in standardization at the following addresses: 

— ISO Online browsing platform: available at 

— IEC Electropedia: available at

3.1 integral female cone

female 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 female cone

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

4 Requirements

4.1 Dimensions and tolerances

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

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

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

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

Dimensions and tolerances are given in Table 1 (integral female cones) and Table 2 (fabricated female 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 female cone types, respectively

4.2 Materials

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 female 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 female 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 cone 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.

5 Designation

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

a) the term of the 60° female 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 female cones only); 

d) the tube outside diameter, in millimetres; 

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


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

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


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

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

6 Figures and tables

6.1 Integral 60° female cone

Dimensions in millimetres, Surface roughness in micrometres, as defined in ISO 1302

Figure 1 — Integral 60° female cone without undercut 

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 2 — Integral 60° female cone with 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 female cone of Figure 1.

NOTE 2 See Table 1 for dimension T.

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


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


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 female 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 - female 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.

Table 1 — Integral 60° female cones

6.2 Fabricated 60° female cone

Figure 5 — Fabricated 60° female cone without undercut 

Dimensions in millimetres, Surface roughness in micrometres, as defined in ISO 1302

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

Figure 6 — Fabricated 60° female cone with undercut 

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

Figure 7 — Pipe end assembly for fabricated 60° female cone (basic relationships) 
Table 2 — Fabricated 60° female cones 
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