ISO/WD 22705-2

Springs — Measurement and test parameters — Part 2: Cold formed cylindrical helical extension springs

This document specifies the measurement and test methods for general characteristics of cold formed helical extension springs made from round wire, excluding dynamic testing.

Ressort - Mesures et paramètres d'essai — Partie 2: Ressort hélicoïdal de traction cylindrique formé à froid

General Information

• Status: Published
• Publication Date: 06-Feb-2023
• ICS: 21.160 - Springs
• Technical Committee: ISO/TC 227 - Springs
• Drafting Committee: ISO/TC 227/WG 3 - Measurement and test parameters for extension spring
• Current Stage: 6060 - International Standard published
• Start Date: 07-Feb-2023
• Due Date: 08-Oct-2022
• Completion Date: 07-Feb-2023

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 22705-2
First edition
2023-02
Springs — Measurement and test
parameters —
Part 2:
Cold formed cylindrical helical
extension springs
Ressort - Mesures et paramètres d'essai —
Partie 2: Ressort hélicoïdal de traction cylindrique formé à froid
Reference number
ISO 22705-2:2023(E)
© ISO 2023
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ISO 22705-2:2023(E)
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© ISO 2023

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Published in Switzerland
© ISO 2023 – All rights reserved
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ISO 22705-2:2023(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms, definitions, symbols and abbreviated terms .................................................................................................... 1

3.1 Terms and definitions ...................................................................................................................................................................... 1

3.2 Symbols and abbreviated terms ............................................................................................................................................. 2

4 Environmental conditions ......................................................................................................................................................................... 3

5 Qualifications of the person(s) performing the work .................................................................................................. 3

6 Geometries of guiding and supporting devices .................................................................................................................. 3

7 Measuring and testing equipment .................................................................................................................................................... 3

8 Measurement and test parameter for technical cold formed cylindrical extension

springs ............................................................................................................................................................................................................................ 4

8.1 Free length (L ) ...................................................................................................................................................................................... 4

8.1.1 General ........................................................................................................................................................................................ 4

8.1.2 Type of characteristic .................................................................................................................................................... 4

8.1.3 Measuring and/or testing equipment .............................................................................................................. 4

8.1.4 Conditions of measurement and testing ....................................................................................................... 4

8.1.5 Method of measurement and testing ............................................................................................................... 4

8.1.6 Test location on the product..................................................................................................................................... 7

8.2 Body length (L ) .................................................................................................................................................................................... 7

8.2.1 General ........................................................................................................................................................................................ 7

8.2.2 Type of characteristic .................................................................................................................................................... 7

8.2.3 Measuring and/or testing equipment .............................................................................................................. 8

8.2.4 Conditions of measurement and testing ....................................................................................................... 8

8.2.5 Method of measurement and testing ............................................................................................................... 8

8.2.6 Test location on the product.................................................................................................................................. 10

8.3 Spring hook length (L ) ............................................................................................................................................................... 10

8.3.1 General ..................................................................................................................................................................................... 10

8.3.2 Type of characteristic ................................................................................................................................................. 10

8.3.3 Measuring and/or testing equipment ........................................................................................................... 11

8.3.4 Conditions of measurement and testing .................................................................................................... 11

8.3.5 Method of measurement and testing ............................................................................................................ 11

8.3.6 Test location on the product.................................................................................................................................. 13

8.4 Hook opening (m) .............................................................................................................................................................................. 13

8.4.1 General .....................................................................................................................................................................................13

8.4.2 Type of characteristic ................................................................................................................................................. 13

8.4.3 Measuring and/or testing equipment ........................................................................................................... 14

8.4.4 Conditions of measurement and testing .................................................................................................... 14

8.4.5 Method of measurement and testing ............................................................................................................ 14

8.4.6 Test location on the product.................................................................................................................................. 15

8.5 Outside diameter (D ).................................................................................................................................................................... 15

8.5.1 General .....................................................................................................................................................................................15

8.5.2 Type of characteristic ................................................................................................................................................. 15

8.5.3 Measurement and/or testing equipment ................................................................................................... 16

8.5.4 Conditions of measurement and testing .................................................................................................... 16

8.5.5 Method of measurement and testing ............................................................................................................ 16

8.5.6 Test location on the product.................................................................................................................................. 20

8.6 Inside diameter (D ) ........................................................................................................................................................................20

8.6.1 General .....................................................................................................................................................................................20

8.6.2 Type of characteristic ................................................................................................................................................. 20

8.6.3 Measuring and/or testing equipment ........................................................................................................... 20

8.6.4 Conditions of measurement and testing .................................................................................................... 20

iii
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ISO 22705-2:2023(E)

8.6.5 Method of measurement and testing ............................................................................................................ 21

8.6.6 Test location on the product.................................................................................................................................. 23

8.7 Total number of coils (n ), number of active coils (n) and coil direction ..........................................23

8.7.1 General .....................................................................................................................................................................................23

8.7.2 Type of characteristic ................................................................................................................................................. 23

8.7.3 Measuring and/or testing equipment ........................................................................................................... 25

8.7.4 Conditions of measurement and testing .................................................................................................... 25

8.7.5 Method of measurement and testing ............................................................................................................ 25

8.7.6 Test location on the product.................................................................................................................................. 26

8.8 Bending radius (r) .............................................................................................................................................................................26

8.8.1 General ..................................................................................................................................................................................... 26

8.8.2 Type of characteristic ................................................................................................................................................. 26

8.8.3 Measuring and/or testing equipment ........................................................................................................... 27

8.8.4 Conditions of measurement and testing .................................................................................................... 27

8.8.5 Method of measurement and testing ............................................................................................................ 27

8.8.6 Test location on the product.................................................................................................................................. 27

8.9 Spring load (F) .....................................................................................................................................................................................28

8.9.1 General .....................................................................................................................................................................................28

8.9.2 Type of characteristic .................................................................................................................................................28

8.9.3 Measuring and/or testing equipment ...........................................................................................................28

8.9.4 Conditions of measurement and testing ....................................................................................................28

8.9.5 Method of measurement and testing ............................................................................................................28

8.9.6 Test location on the product..................................................................................................................................29

8.10 Spring pitch (p) / distance between the coils (u) .................................................................................................29

8.10.1 General .....................................................................................................................................................................................29

8.10.2 Type of characteristic .................................................................................................................................................29

8.10.3 Measuring and/or testing equipment ...........................................................................................................30

8.10.4 Conditions of measurement and testing ....................................................................................................30

8.10.5 Method of measurement and testing ............................................................................................................30

8.10.6 Test location on the product..................................................................................................................................30

8.11 Loop/ Hook position ....................................................................................................................................................................... 31

8.11.1 General ..................................................................................................................................................................................... 31

8.11.2 Type of characteristic ................................................................................................................................................. 31

8.11.3 Measuring and/or testing equipment ........................................................................................................... 31

8.11.4 Conditions of measurement and testing .................................................................................................... 32

8.11.5 Method of measurement and testing ............................................................................................................ 32

8.11.6 Test location on the product.................................................................................................................................. 32

8.12 Shear-off burr ....................................................................................................................................................................................... 32

8.12.1 General ..................................................................................................................................................................................... 32

8.12.2 Type of characteristic ................................................................................................................................................. 32

8.12.3 Measuring and/or testing equipment ........................................................................................................... 33

8.12.4 Conditions of measurement and testing .................................................................................................... 33

8.12.5 Method of measurement and testing ............................................................................................................ 33

8.12.6 Test location on the product..................................................................................................................................34

Annex A (Informative) Calculation of spring rate R .........................................................................................................................35

Annex B (Informative) Calculation of initial tension force (F ) ............................................................................................36

Annex C (Informative) Types of hooks ............................................................................................................................................................38

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ISO 22705-2:2023(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

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expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see

www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 227, Springs.
A list of all parts in the ISO 22705 series can be found on the ISO website.

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.
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INTERNATIONAL STANDARD ISO 22705-2:2023(E)
Springs — Measurement and test parameters —
Part 2:
Cold formed cylindrical helical extension springs
1 Scope

This document specifies the measurement and test methods for general characteristics of cold formed

helical extension springs made from round wire, excluding dynamic testing.
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 3611, Geometrical product specifications (GPS) — Dimensional measuring equipment: Micrometers for

external measurements — Design and metrological characteristics

ISO 13385-1, Geometrical product specifications (GPS) — Dimensional measuring equipment — Part 1:

Design and metrological characteristics of callipers
ISO 16249, Springs — Symbols
ISO 26909, Springs — Vocabulary
3 Terms, definitions, symbols and abbreviated terms
3.1 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 26909 and the following 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/
3.1.1
helical extension spring

extension spring normally made of wire of circular cross-section, wound around an axis, with or

without spaces between its coils (open or closed wound)

[SOURCE: ISO 26909:2009, 3.13, modified — limited to wires with circular cross-section]

3.1.2
test parameter

parameter with a tolerance for which there is an immediate conclusion after test (within tolerance or

out of tolerance)

Note 1 to entry: Test can be done without measurement (i.e. with GO/NO GO gauges).

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ISO 22705-2:2023(E)
3.2 Symbols and abbreviated terms

For the purposes of this document, the symbols given in ISO 16249, Figure 1 and Table 1 apply.

Table 1 — Symbols and abbreviated terms
Symbols Units Designations
D mm outside diameter of spring
D mm inside diameter of spring
d mm diameter of wire
d mm maximum diameter of wire
max
d mm actual wire diameter
wire
F N spring load or force
F = F – s R N initial tension force (preload) (see Annex B)
i 1 1
F , F ,… N specified spring loads for the specified spring lengths, L , L ,…
1 2 1 2
F N maximum permissible spring force for the maximum permissible spring length L
n n
F N maximum specified spring load
max
F N minimum specified spring load
min
L mm free length
L mm maximum acceptable spring length measured spring hooks inner radii for F
n n
L , L ,… mm specified spring lengths for the spring loads, F , F ,…
1 2 1 2
L mm distance from inner radius of loop to spring body
L mm body length when unloaded but subject to initial tension force
L mm maximum specified spring length
max
L mm minimum specified spring length
min
m mm hook opening
n – number of active coils
n – total number of coils
p mm spring pitch
ΔF ΔF
N/mm spring rate (see Annex A)
R==
ΔL Δs
r mm bending radius
s mm deflection of spring
s mm maximum test spring deflection for the spring loads, F
n n

s , s ,… mm specified spring deflections for the specified spring loads, F , F ,…

1 2 1 2
s mm deflection of spring (stroke) between two loads
u mm distance between the coils
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ISO 22705-2:2023(E)
Figure 1 — Symbols for helical extension spring
4 Environmental conditions

The spatial distribution and equipment of the facility shall permit a reliable implementation of the

measurements and tests.

Measurements and tests should be carried out at ambient temperature in a normal workshop

environment.

Special tests (e.g. in air-conditioned rooms or other special environments) shall be agreed upon

between the manufacturer and the customer.
Measuring and testing equipment should be subject to regular inspection.
5 Qualifications of the person(s) performing the work

The measurements and tests shall be carried out by a person who has been instructed/trained in the

use of the measuring and testing equipment, as well as regarding methods and test requirements.

The qualifications or additional knowledge and skills should be documented in appropriate qualification

or training documents, depending on the requirements.
6 Geometries of guiding and supporting devices

If guiding and supporting devices (e.g. test pins, guide sleeves, ring grooves) are used, the properties

(e.g. geometry, material) shall be agreed upon between the manufacturer and the customer to include

special cases. The alignment of guiding and supporting devices is aimed to improve the reproducibility

of the measures (e.g. diameter of pins inserted inside the hooks to measure the loads).

7 Measuring and testing equipment

Suitable measuring equipment shall be selected. Measuring equipment shall conform to ISO 3611 and

ISO 13385-1.

If there is a customer requirement, the methods and measuring equipment shall be agreed on separately.

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ISO 22705-2:2023(E)
8 Measurement and test parameter for technical cold formed cylindrical
extension springs
8.1 Free length (L )
8.1.1 General
The free length L is a measurement and test parameter.
8.1.2 Type of characteristic

The free length L is the length between the two internal hooks when no load is applied (see Figure 2);

other cases should be agreed upon between the manufacturer and the customer. If it’s not possible to

measure L inside the hooks, it shall be measured outside the hooks minus two times wire diameter

(2d).
a) Full loop b) Raised hook
Figure 2 — Free length (L )
8.1.3 Measuring and/or testing equipment
The following measuring equipment can be used:
— micrometer gauge;
— calliper;
— electronic measuring sensor;
— manual/automatic force gauge;
— optical measuring instruments/ measurement microscope/camera systems;
The following testing equipment can be used:
— attributive gauges (“GO/NO GO” gauges)
8.1.4 Conditions of measurement and testing
The free length L shall be evaluated at ambient temperature as delivered.
8.1.5 Method of measurement and testing

The measurement can be carried out without contact using optical procedures, capacitive or electrically

by contact (with minimal force) without deflection or by contact with the measuring surfaces (at a

known/unknown measuring force).
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ISO 22705-2:2023(E)

When there is a spring self-weight effect, the measurement of free length should be carried out in

horizontal position on an appropriate flat surface.

If the customer specifies a setting length to test the spring, the setting condition shall be agreed upon

between the manufacturer and the customer.

NOTE Generally, extension springs do not have a setting process because it reduces the initial tension force.

Calliper: the unloaded spring is held with the inner measuring legs of the calliper between the highest

points of the inner edges of the loops (see Figure 3).
GO/NO GO gauges can be used as shown in Figure 4.
a) Loop position 0°
b) Loop position 90°
Figure 3 — Method of measurement with calliper (example)
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ISO 22705-2:2023(E)

a) Tolerance upper limit check with gauge b) Tolerance upper limit check with gauge

(L ≤ L ) NO GO/within tolerance (L > L ) GO/out of tolerance
0 0max 0 0max
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ISO 22705-2:2023(E)

c) Tolerance lower limit check with gauge d) Tolerance lower limit check with gauge

(L ≥ L ) GO/within tolerance (L < L ) NO GO/out of tolerance
0 0min 0 0min
Figure 4 — Method of testing the free length (L ) with gauges (examples)
8.1.6 Test location on the product

The test direction is in the axial direction of the finished spring. When measuring equipment is used

that induces a measuring force, then the applied force should not deflect the spring.

When optical measuring equipment (camera systems) is used, the measurement axis is perpendicular

to the spring axis.
8.2 Body length (L )
8.2.1 General
The body length L is a measurement and test parameter.
8.2.2 Type of characteristic

The body length L is the maximum overall length of the entire spring body (excluding hooks), measured

perpendicular to the axis of the spring when no load is applied (see Figure 5).

Where it is not possible to measure the L the following formula is applied: L = L – L – L

B B 0 H1 H2
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ISO 22705-2:2023(E)
a) Full loop b) Raised hook
Figure 5 — Body length (L )
8.2.3 Measuring and/or testing equipment
The following measuring equipment can be used:
— calliper;
— electronic measuring sensor;
...