ISO 11891:2012

INTERNATIONAL ISO
STANDARD 11891
First edition
2012-04-15
Hot formed helical compression
springs — Technical specifications
Ressorts de compression hélicoïdaux formés à chaud —
Spécifications techniques
Reference number
©
ISO 2012
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ii © ISO 2012 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3  Terms, definitions and symbols . 1
3.1  Terms and definitions . 1
3.2  Symbols and units . 1
4 Material . 2
4.1 Adoption of material . 2
4.2  Diameter and tolerance of bars . 2
5  Spring construction . 2
5.1 Direction of helix . 2
5.2  Types of coil end . 3
6 Spring characteristics . 3
6.1 General . 3
6.2  Length at a specified load . 3
6.3  Load at a specified length . 3
6.4 Spring rate . 3
7 Tolerances of spring dimensions and characteristics . 3
7.1 General . 3
7.2 Free length . 4
7.3 Diameter of coils . 4
7.4 Total coils . 4
7.5  Perpendicularity . 4
7.6 Parallelism . 4
7.7  Irregularity of pitch . 5
7.8 Solid length . 5
7.9 Tolerances on spring characteristics . 5
8  Requirements for manufacturing . 6
8.1 Heat treatment . 6
8.2 Hardness . 6
8.3  Decarburization . 6
8.4  Grain size . 6
8.5  Surface conditions . 6
8.6  End surface machining . 6
8.7 Shot peening . 6
8.8 Setting (presetting) . 6
8.9  Surface protection . 6
9 Test methods . 6
9.1 General . 6
9.2 Spring characteristics . 7
9.3 Dimensions and shapes . 7
9.4  Surface conditions . 8
9.5 Hardness . 8
9.6  Decarburization . 8
9.7  Grain size . 8
9.8 Shot peening . 8
9.9  Surface protection . 8
Bibliography . 9
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 11891 was prepared by Technical Committee ISO/TC 227, Springs.
iv © ISO 2012 – All rights reserved

INTERNATIONAL STANDARD ISO 11891:2012(E)
Hot formed helical compression springs — Technical
specifications
1 Scope
This International Standard specifies the materials, shapes, spring characteristics, tolerances, manufacturing
requirements and test methods for common helical compression springs, which are made from hot coiled
round section steel bar, and then quenched and tempered (hereinafter simply “springs”).
The following limit values apply to springs conforming to this International Standard:
— free length: ≤ 900 mm;
— spring index: 3 to 12;
— slenderness ratio: 0,8 to 4;
— active coils: ≥ 3;
— spring pitch: < 0,5D;
— wire diameter: 8 mm to 60 mm;
— mean diameter of coil: ≤ 460 mm.
This International Standard is not applicable to coil springs with special performance requirements, such as
railway and automotive suspensions.
2 Normative references
The following referenced documents are indispensable for the application 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 643, Steels — Micrographic determination of the apparent grain size
ISO 7500-1, Metallic materials — Verification of static uniaxial testing machines — Part 1: Tension/compression
testing machines — Verification and calibration of the force-measuring system
ISO 18265, Metallic materials — Conversion of hardness values
ISO 26909, Springs — Vocabulary
3  Terms, definitions and symbols
3.1  Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 26909 apply.
3.2  Symbols and units
For the purposes of this document, the symbols and units given in Table 1 apply.
Table 1 — Symbols and units
Symbol Parameter Unit
D mean diameter of coil mm
D outside diameter of spring mm
e
d diameter of wire mm
d maximum diameter of wire (or bar) mm
max
F spring load N
L solid length mm
c
L free length mm
n total coils —
t
R
spring rate N/mm
s
deflection mm
e perpendicularity mm
e parallelism mm
4 Material
4.1 Adoption of material
Unless otherwise agreed by the purchaser and the supplier, springs should be made from the material
conforming to ISO 683-14.
4.2  Diameter and tolerance of bars
4.2.1  Hot rolled bars
The tolerances of the dimensions and shapes of specified hot rolled bars should be according to ISO 1035-4,
unless otherwise agreed between the purchaser and the supplier.
4.2.2  Bars with cold-worked surface
Tolerances of the dimensions and shapes of cold-worked surface bars (i.e. with cold-drawn, turned, peeled,
ground or a combination thereof) specified should be as specified in Table 2, unless otherwise agreed between
the purchaser and the supplier.
Table 2 — Tolerances of steel bars with cold-worked surface
Dimensions in millimetres
Diameter Tolerance
8 ≤ d < 12,5 ± 0,06
12,5 ≤ d < 26 ± 0,08
26 ≤ d < 48 ± 0,10
48 ≤ d ≤ 60 ± 0,15
5  Spring construction
5.1 Direction of helix
Normally, the direction of helix should be right-hand (clockwise). If several springs are to be nested together, the
direction of helix alternates by spring, with the outside spring usually being in the right-hand direction. If the direction
of helix of the spring is requested to be left-hand, this requirement shall be indicated on the design drawing.
2 © ISO 2012 – All rights reserved

5.2  Types of coil end
The usual types of spring coil end are illustrated in Figure 1. If only one type is indicated on the drawings, this
type shall apply to both ends of the spring; a combination of two coil ends, e.g. the coil end in Figure 1 a) and
the coil end in Figure 1 b), is possible.
a) Closed end (not ground) b) Closed end (ground) c) Closed end (tapered)
d) Open end (not ground) e) Open end (ground) f) Open end (tapered)
Figure 1 — Types of coil end
6 Spring characteristics
6.1 General
The length at a specified load or the load at a specified length should be agreed between the purchaser and
the supplier according to 6.2 or 6.3.
6.2  Length at a specified load
If the length at a specified load is required, the deflection under the specified load should be within
...