SIST EN 13001-3-5:2026

SLOVENSKI STANDARD
01-februar-2026
Žerjavi - Konstrukcija, splošno - 3-5. del: Mejna stanja in dokaz varnosti kovanih in
litih kavljev
Cranes - General design - Part 3-5: Limit states and proof of competence of forged and
cast hooks
Krane - Konstruktion allgemein - Teil 3-5: Grenzzustände und Sicherheitsnachweis von
geschmiedeten und gegossenen Haken
Appareils de levage à charge suspendue - Conception générale - Partie 3-5 : États
limites et vérification des crochets forgés et moulés
Ta slovenski standard je istoveten z: EN 13001-3-5:2025
ICS:
53.020.20 Dvigala Cranes
53.020.30 Pribor za dvigalno opremo Accessories for lifting
equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 13001-3-5
EUROPEAN STANDARD
NORME EUROPÉENNE
December 2025
EUROPÄISCHE NORM
ICS 53.020.20 Supersedes EN 13001-3-5:2016+A1:2021
English Version
Cranes - General design - Part 3-5: Limit states and proof
of competence of forged and cast hooks
Appareils de levage à charge suspendue - Conception Krane - Konstruktion allgemein - Teil 3-5:
générale - Partie 3-5 : États limites et vérification des Grenzzustände und Sicherheitsnachweis von
crochets forgés et moulés geschmiedeten und gegossenen Haken
This European Standard was approved by CEN on 17 November 2025.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 13001-3-5:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 5
Introduction . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions, symbols and abbreviations . 9
3.1 Terms and definitions . 9
3.2 Symbols and abbreviations . 10
4 General requirements . 13
4.1 Materials . 13
4.1.1 Material standards and grades . 13
4.1.2 General material requirements . 13
4.1.3 Testing of mechanical properties . 15
4.2 Hook body geometry . 15
4.3 Hook shank machining . 17
4.4 Nut . 18
5 Static strength . 18
5.1 General . 18
5.2 Vertical design force . 18
5.3 Horizontal design force . 19
5.3.1 General . 19
5.3.2 Tilting resistance of hook suspension . 20
5.4 Bending moment of the shank . 20
5.4.1 General . 20
5.4.2 Bending moment due to horizontal force . 21
5.4.3 Bending moment due to inclination of hook suspension . 21
5.4.4 Bending moment due to eccentricity of vertical force . 22
5.4.5 Exceptional case for ramshorn hooks . 23
5.4.6 Design bending moment of the shank . 23
5.5 Hook body, design stresses . 24
5.5.1 Loadings. 24
5.5.2 Stress determination methods . 25
5.5.3 Design stresses applying curved beam bending theory . 25
5.6 Hook shank, design stresses . 26
5.7 Hook, proof of static strength . 26
5.7.1 General for hook body and shank . 26
5.7.2 The use of static limit design force for verification of the hook body . 27
6 Fatigue strength . 28
6.1 General . 28
6.2 Vertical fatigue design force. 28
6.3 Horizontal fatigue design force . 28
6.4 Fatigue design bending moment of shank . 29
6.4.1 Bending moment due to horizontal force . 29
6.4.2 Bending moment due to inclination of hook suspension . 29
6.4.3 Bending moment due to eccentricity of vertical force . 29
6.5 Proof of fatigue strength, hook body . 30
6.5.1 Design stress calculation . 30
6.5.2 Stress history in general . 30
6.5.3 Stress history based upon classified duty . 31
6.5.4 Limit fatigue design stress . 32
6.5.5 Execution of the proof . 34
6.5.6 The use of fatigue limit design force for verification of the hook body . 34
6.6 Proof of fatigue strength, hook shank . 35
6.6.1 General . 35
6.6.2 Design stress calculation . 36
6.6.3 Applied stress cycles. 36
6.6.4 Basic fatigue strength of material . 37
6.6.5 Stress concentration effects from geometry . 37
6.6.6 Fatigue strength of notched shank . 38
6.6.7 Mean stress influence . 39
6.6.8 Transformation to stresses at zero mean stress . 40
6.6.9 Stress history parameter in general . 41
6.6.10 Stress history parameter based upon classified duty . 41
6.6.11 Execution of the proof . 42
Annex A (informative) Sets of single hooks . 43
A.1 A series of single hooks of type RS/RSN, dimensions of hook bodies . 43
A.2 A series of single hooks of type RF/RFN, dimensions of hook bodies . 44
A.3 A series of single hooks of type B, dimensions of hook bodies . 47
Annex B (informative) A series of ramshorn hooks of type RS/RSN and RF/RFN, dimensions
of hook bodies . 49
Annex C (informative) Dimensional tolerances of hook bodies . 51
Annex D (informative) Static limit design forces of hook bodies . 53
D.1 Static limit design forces of hook bodies for hooks of type RS and RF . 53
D.2 Static limit design forces of hook bodies for a series of hooks of type B, with
additional materials . 54
Annex E (informative) Fatigue limit design forces of hook bodies . 55
E.1 Fatigue limit design forces of hook bodies for forged hooks of type RS and RF . 55
E.2 Fatigue limit design forces of hook bodies for a series of hooks of type B, with
additional, forged materials . 57
E.3 Fatigue limit design forces of hook bodies for cast hooks of type RS and RF . 58
E.4 Fatigue limit design forces of hook bodies for a series of hooks of type B, with
additional, cast materials . 59
Annex F (informative) Sets of hook shank and thread designs . 60
F.1 A series of hook shank and thread designs, a knuckle thread . 60
F.2 A series of hook shank and threads, a metric thread . 62
F.3 A series of hook shank and thread designs, a modified metric thread . 64
F.4 Hook shank and thread designs for hooks of type B . 66
Annex G (informative) Bending of curved beams . 68
G.1 Basic formulae for stresses . 68
G.2 Approximation of the reference moment of inertia . 69
Annex H (informative) Calculation of hook suspension tilting resistance, examples . 71
H.1 Example: Articulation of hook by a hinge . 71
H.2 Example: Articulation of a hook suspension by a balanced rope reeving . 72
Annex I (informative) Guidance for the selection of a hook body size using Annexes D and E . 74
I.1 General . 74
I.2 Case description . 74
I.3 Proof of static strength . 74
I.4 Proof of fatigue strength . 75
I.5 Final selection of hook . 75
Annex J (informative) Classification of hook materials. 76
Annex K (informative) Workmanship and testing of hooks . 77
K.1 Forged hooks . 77
K.2 Cast hooks . 77
K.3 Scope of material testing and sampling . 78
K.4 Test load . 78
Annex L (informative) Information for use . 80
L.1 Maintenance and inspection . 80
L.2 Marking . 80
L.3 Safe use . 82
Annex M (informative) Overview of standards published by CEN/TC 147 . 83
M.1 General . 83
M.2 Selecting a suitable standard . 83
Annex N (informative) List of significant hazards . 86
Annex ZA (informative) Relationship between this European Standard and the essential
requirements of Directive 2006/42/EC aimed to be covered . 87
Annex ZB (informative) Relationship between this European Standard and the essential
requirements of Regulation (EU) 2023/1230 aimed to be covered . 88
Bibliography . 89
European foreword
This document (EN 13001-3-5:2025) has been prepared by Technical Committee CEN/TC 147 “Crane —
Safety”, the secretariat of which is held by SFS.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by June 2026 and conflicting national standards shall be
withdrawn at the latest by June 2026.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 13001-3-5:2016+A1:2021.
This document has been prepared under a standardization request addressed to CEN by the European
Commission. The Standing Committee of the EFTA States subsequently approves these requests for its
Member States.
For the relationship with EU Legislation, see informative Annex ZA and Annex ZB, which are integral
parts of this document.
The major changes in this document compared to EN 13001-3-5:2016+A1:2021 are:
— move of technical content of Clauses 4.1.3, 4.2 and 4.3 into informative annexes;
— removal of the concept “Cold forming by proof loading” out of the standard;
— changes in 6.5.4, 6.5.5 and 6.6.4 regarding design factors for fatigue design;
— move of Clauses 7 and 8 into informative annexes;
— recalculated numeric values in Annex E due to changes of design factors;
— changes in Annex ZA, addition of a new Annex ZB for Regulation (EU) 2023/1230.
This European Standard is one part of the EN 13001 series. The other parts are as follows:
— Part 1: General principles and requirements
— Part 2: Load actions
— Part 3-1: Limit states and proof of competence of steel structures
— Part 3-2: Limit states and proof of competence of wire ropes in reeving systems
— Part 3-3: Limit states and proof of competence of wheel/rail contacts
— Part 3-4: Limit states and proof of competence of machinery — Bearings
— Part 3-6: Limit states and proof of competence of machinery — Hydraulic cylinders
Under revision.
— Part 3-8: Limit states and proof of competence of machinery — Shafts
For the overview of standards published by CEN/TC 147, see Annex M.
Information on safe use of crane hooks is given in Annex L.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland,
Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North
Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the United
Kingdom.
Under preparation. Stage at the time of publication: FprEN 13001-3-8.
Introduction
This document has been prepared to provide a means for the mechanical design and theoretical
verification of crane hooks to conform to essential health and safety requirements. This document also
establishes interfaces between the user (purchaser) and the designer, as well as between the designer
and the component manufacturer, in order to form a basis for selecting cranes and components.
This document is a type C standard as stated in EN ISO 12100:2010.
This document is of relevance, in particular, for the following stakeholder groups representing the market
players with regard to machinery safety:
— machine manufacturers (small, medium and large enterprises);
— health and safety bodies (regulators, accident prevention organizations, market surveillance, etc.).
Others can be affected by the level of machinery safety achieved with the means of the document by the
above-mentioned stakeholder groups:
— machine users/employers (small, medium and large enterprises);
— machine users/employees (e.g. trade unions, organizations for people with special needs);
— service providers, e.g. for maintenance (small, medium and large enterprises);
— consumers (in case of machinery intended for use by consumers).
The above-mentioned stakeholder groups have been given the possibility to participate at the drafting
process of this document.
The machinery concerned and the extent to which hazards, hazardous situations or hazardous events are
covered are indicated in the Scope of this document.
When requirements of this type-C standard are different from those which are stated in type-A or type-B
standards, the requirements of this type-C standard take precedence over the requirements of the other
standards for machines that have been designed and built according to the requirements of this type-C
standard.
1 Scope
This document covers shank hooks made of steel forgings or steel castings, including stainless steel, with
shanks machined for a thread/nut suspension of the hook.
Plate hooks, which are those, assembled of one or several parallel parts of rolled steel plates, are not
covered by this document.
The significant hazardous situations and hazardous events that could result in risks to persons during
intended use and reasonably foreseeable misuse are identified in Annex N. Clauses 4 to 6 of this
document provide requirements and methods to reduce or eliminate the risks of exceeding the limits of
strength (yield, ultimate, fatigue, brittle fracture) considering temperature limits of material.
The hazards covered by this document are identified in Annex N. This document is applicable to hooks
installed in cranes manufactured after the date of approval of this European Standard by CEN and serves
as a reference base for product standards of particular crane types.
This part of EN 13001 deals only with the limit state method in accordance with EN 13001-1:2015.
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.
EN 10025-3:2019, Hot rolled products of structural steels — Part 3: Technical delivery conditions for
normalized/normalized rolled weldable fine grain structural steels
EN 10213:2007+A1:2016, Steel castings for pressure purposes
EN 10222-4:2017+A1:2021, Steel forgings for pressure purposes — Part 4: Weldable fine grain steels with
high proof strength
EN 10250-2:2022, Open die steel forgings for general engineering purposes — Part 2: Non-alloy quality and
special steels
EN 10250-3:2022, Open die steel forgings for general engineering purposes — Part 3: Alloy special steels
EN 10340:2007, Steel castings for structural uses
EN 12680-1:2003, Founding — Ultrasonic examination — Part 1: Steel castings for general purposes
EN 13001-1:2015, Cranes — General design — Part 1: General principles and requirements
EN 13001-2:2021, Crane safety — General design — Part 2: Load actions
EN ISO 148-1:2016, Metallic materials — Charpy pendulum impact test — Part 1: Test method (ISO 148-
1:2016)
EN ISO 642:2024, Steel — Hardenability test by end quenching (Jominy test) (ISO 642:2024)
EN ISO 643:2024, Steels — Micrographic determination of the apparent grain size (ISO 643:2024)
EN ISO 683-2:2018, Heat-treatable steels, alloy steels and free-cutting steels — Part 2: Alloy steels for
quenching and tempering (ISO 683-2:2016)
EN ISO 898-2:2022, Fasteners — Mechanical properties of fasteners made of carbon steel and alloy steel —
Part 2: Nuts with specified property classes (ISO 898-2:2022)
EN ISO 21920-2:2022, Geometrical product specifications (GPS) — Surface texture: Profile — Part 2:
Terms, definitions and surface texture parameters (ISO 21920-2:2021, Corrected version 2022-06)
EN ISO 6892-1:2019, Metallic materials — Tensile testing — Part 1: Method of test at room temperature
(ISO 6892-1:2019)
EN ISO 12100:2010, Safety of machinery — General principles for design — Risk assessment and risk
reduction (ISO 12100:2010)
ISO 965-1:2013, ISO general purpose metric screw threads — Tolerances — Part 1: Principles and basic
data
ISO 4306-1:2007, Cranes — Vocabulary — Part 1: General
3 Terms and definitions, symbols and abbreviations
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in EN ISO 12100:2010 and
ISO 4306-1:2007, 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
hook shank
upper part of the hook, from which the hook is suspended to the hoist medium of the crane
3.1.2
hook body
lower, curved part of the hook below the shank
3.1.3
hook seat
bottom part of the hook body, where the load lifting attachment is resting
3.1.4
hook articulation
feature of the hook suspension, allowing the hook to tilt along the inclined load line
3.1.5
total deformation ratio
ratio of the area of the cast cross section to the forged cross section
Note 1 to entry: The following terms might also be used in technical literature for the same: reduction rate,
reduction ratio, forging reduction.
3.2 Symbols and abbreviations
Table 1 — Symbols and abbreviations
Symbols,
Description
abbreviations
A Cross section area of the unmachined shank
d1
A Cross section area of the critical section of hook shank
d4
A Minimum impact toughness of material
v
a Acceleration
a Seat circle diameter
a Throat opening
a Height of the hook point
b Maximum width in the critical hook body section
max
bref Reference width
C Total number of working cycles during the design life of crane
C Relative tilting resistance of the hook suspension
t
c Coefficient for load eccentricity
e
D Cumulative damage in fatigue (Palmgren-Miner hypothesis)
d Diameter of the unmachined shank
d Principal diameter of thread
d Diameter of the undercut section of the shank
d Thread core diameter
e Distance of the vertical load line from the centre line of the shank
R
F Vertical force
F Vertical force on hook due to occasional or exceptional loads
H
F Basic limit design forces, static
Rd,s,0
F , F Limit design forces, static/fatigue
Rd,s Rd,f
F Vertical design force for the proof of static strength
Sd,s
F Vertical design force for the proof of fatigue strength
Sd,f
f , f , f Factors of material type influence (forged/cast)
M MB MS
f , f , f Factors of further influences
1 2 3
f Limit design stress
Rd
f Yield stress
y
fu Ultimate strength
g Acceleration due to gravity, g = 9,81 m/s
Symbols,
Description
abbreviations
H Horizontal design force of hook
Sd,s
H Horizontal design force for the proof of fatigue strength
Sd,f
h1, h2 Section heights of the hook body
Vertical distance from the seat bottom of the hook body to the centre of the
h
articulation
Vertical distance from the seat bottom of the hook body to the section of the hook
h
s
shank where the bending stress is governing the design
i Index for a lifting cycle or a stress cycle
I Reference moment of inertia for curved beam
I Moment of inertia of the unmachined shank
d1
I Moment of inertia of the critical section of hook shank
d4
k Conversion factor for stress spectrum and classified duty
C
kh, ks Stress spectrum factors
kQ Load spectrum factor, in accordance with EN 13001-1:2015
k * Specific spectrum ratio factor with m = 5
lg Log to the base of 10
M , M , M , M Bending moments of hook shank
1 2 3 4
M , M , M Bending moments of hook shank for the proof of fatigue strength, lifting cycle i
1,f,i 2,f,i 3,f,i
M Static design bending moment
Sd,s
m Slope parameter of the characteristic fatigue design curve
m Mass of rated hoist load
RC
m Mass of the hook load in a lifting cycle i
i
N Total number of stress cycles/lifting cycles
N Reference number of stress cycles, N = 2 × 10
D D
p Pitch of thread
p Average number of accelerations related to one lifting cycle
a
R Radius of hook body curvature
R Average depth of surface profile in accordance with EN ISO 21920-2:2022
a
R Maximum depth of surface profile in accordance with EN ISO 21920-2:2022
z
r Relief radius of the undercut
r Thread bottom radius
th
s Length of undercut
s , s Stress history parameters
h s
Symbols,
Description
abbreviations
s Load history parameter
Q
t Depth of thread
T Operation temperature
u , u Depths of notches
S T
α Angle
α , α Stress concentration factors
S T
β Angle or direction of hook inclination
β , β , β Notch effect factors
n nS nT
ϕ Dynamic factor for hoisting an unrestrained grounded load
ϕ Dynamic factor for changes of acceleration of a movement
γ Risk coefficient
n
γ Partial safety factor
p
γ General resistance coefficient
m
γ Specific resistance coefficient
sm
γ , γ Fatigue strength specific resistance factors
Hf Sf
η Edge distance of a hook body section
ν Factor for load component
ν , ν Relative numbers of stress cycles
h s
μ Factor for mean stress influence
σ Shank stress due to axial force
a
σ Shank stress due to bending moment
b
σ Mean stress in a stress cycle
m
σ Stress amplitude in a stress cycle
A
σ Design stress
Sd
σ Basic fatigue strength amplitude, un-notched piece
M
σ Total stress range in a pulsating stress cycle
p
σ Fatigue strength amplitude, notched piece
W
σ , σ , σ Transformed stress amplitudes
Tmax T1 T2
Δσ Characteristic fatigue strength
c
Δσ Limit fatigue design stress
Rd
Δσ Stress range in a lifting cycle i
Sd,i
Δσ Maximum stress range
Sd,max
4 General requirements
4.1 Materials
4.1.1 Material standards and grades
Material grades and qualities for hooks shall be either in accordance with Table 2, or, for other material
standards, such that the requirements of 4.1.2 shall be fulfilled and the mechanical properties and the
chemical composition shall be specified in the same way as in relevant European Standards.
NOTE Classification of hook materials based on strength properties is given in Annex J.
Table 2 — Suitable materials for hooks
Material standard Selected qualities
EN 10025-3:2019 S355N S420N
P355NH P420NH
EN 10222-4:2017+A1:2021
P355QH P420QH
Forged hooks EN 10250-2:2022 S355J2N
EN ISO 683-2:2018 25CrMo4+QT 34CrNiMo6+QT
34CrMo4+QT
EN 10250-3:2022 30CrNiMo8+QT
36CrNiMo4+QT
EN 10213:2007+A1:2016 G20Mn5 + N G20Mn5 + QT
Cast hooks
EN 10340:2007 G18NiMoCr3–6 + QT GX4CrNi13–4 + QT
4.1.2 General material requirements
The hook material in the finished product shall have ductility to permanently deform before losing the
ability to carry the load, at the temperatures specified for the use of the hook. Particularly the hook
material shall fulfil the following conditions:
— the ratio of ultimate strength (f ) to yield stress (f ) f /f ≥ 1,1. For the materials, which do not fulfil
u y u y
this condition, the design value of f shall be limited to f /1,1;
y u
— the percentage elongation at fracture A ≥ 10 % on a gauge length LS5,65× (where S is the
0 0
original cross-sectional area).
The hook material, after heat treatment, shall have minimum Charpy-V impact energy in accordance with
EN ISO 148-1:2016 and as specified in Table 3.
=
Table 3 — Minimum impact energy for hook material
Operation Impact test Minimum impact
temperature temperature energy KV
T ≥ 0 °C +20 °C 27 J
T ≥ −20 °C −0 °C 27 J
T ≥ −30 °C −20 °C 27 J
T ≥ −40 °C −30 °C 27 J
To satisfy the requirements of the operating temperature, a steel shall be selected, which after suitable
heat treatment, shall be consistent with achieving the chosen mechanical property grade for the selected
hook form, taking into account its individual ruling thickness.
The steel shall be fully killed, stabilized against strain age embrittlement, ensured by having suitable mass
content of aluminium (in general between 0,02 % and 0,05 %). The steel shall contain no more sulphur
and phosphorus than the limits given in Table 4.
Table 4 — Sulphur and phosphorus content
Maximum mass content as determined by
Element
Cast analysis Check analysis
Sulphur (S) 0,020 [%] 0,025 [%]
Phosphorus (P) 0,020 [%] 0,025 [%]
Sum of S + P 0,035 [%] 0,045 [%]
Where quenched and tempered steel is used, the hardenability of the steel shall fulfil the requirement of
the Jominy-ratio given in Table 5. The Jominy-ratio J30/J1,5 is the ratio between J30 and J1,5, where J30
and J1,5 mean the hardness at depths 30 mm and 1,5 mm correspondingly, determined by Jominy face-
quenching test in accordance with EN ISO 642:2024.
The tests shall be carried out per melt. For more information on hardening properties and hardness
profiles, see EN ISO 683-2:2018. Where the mechanical properties of cast hooks are tested for each single
hook, the hardenability may be verified by HB-testing in accordance with EN ISO 6506-1:2014 in the
section of the test specimen at 1,5 mm and 30 mm depth from the surface. The hardness ratio shall fulfil
the minimum requirement (Jominy-ratio) given in Table 5.
Table 5 — Hardenability of quenched and tempered materials, Jominy-ratio
Ultimate strength f Minimum required
u
N/mm Jominy-ratio J30/J1,5
540 ≤ f < 800 65 %
u
800 ≤ f 93 %
u
Hooks in the final condition shall have a grain size of
— 6 or finer for forged materials;
— 5 or finer for cast materials;
with grain size determined in accordance with EN ISO 643:2024.
NOTE Guidance on manufacturing processes of hooks is given in Annex K.
4.1.3 Testing of mechanical properties
The test pieces for tensile and impact testing shall be taken longitudinally at the upper part of the hook
shank, at a distance of 1/3 radius from the shanks surface. Where the shank is too small, tests may be
carried out on sample material selected from the same material melt, with the same total deformation
ratio, the same diameter as the reference shank and subjected to heat treatment together with the hook.
A tensile test of material shall be carried out in accordance with EN ISO 6892-1:2019. The impact test
shall be carried out in accordance with EN ISO 148-1:2016.
4.2 Hook body geometry
Proportions of a hook body shall be such that stresses in any sections do not exceed stresses in the
governing sections specified in 5.5.1. For that purpose, the following shall apply:
a) The seat of a hook body shall be of circular shape.
b) In a single hook, the centre of curvature shall coincide with the centreline of the machined shank.
c) In a ramshorn hook, the seat circle shall be tangential in respect to the outer edge of the unmachined
shank.
d) A ramshorn hook shall be symmetrical in respect to the centre line of the shank.
NOTE 1 Annexes A and B present example sets of hook body dimensions, which fulfil the requirements of this
clause. Annex C gives recommendations for dimensional tolerances of hook bodies. The commonly used hook body
and shank designs listed in Annexes A, B and F are only examples and are not referred to as requirements of this
document. Annex I give guidance for the selection of a hook size, where a hook body is in accordance with Annex A
or B.
NOTE 2 The selection of hook form is not limited to those shown in Annexes A and B.
Figure 1 — Hook dimensions
The diameter of the unmachined shank (d ) shall be proportioned to circle diameter (a ) as follows:
1 1
d ≥ 0,55 a .
1 1
The bifurcation point between the inner edge and the seat circle (a ) shall be from the horizontal in
minimum as follows: for a single hook α ≥ 60°, for a ramshorn hook α ≥ 90°.
The full throat opening (a ), without consideration to a latch shall be proportioned to the seat circle
diameter as follows: a ≤ 0,85 a . The effective throat opening with a latch shall be in minimum a ≥ 0,7 a .
2 1 o 1
The point height of a hook (a ) shall be in minimum as follows: a ≥ a .
3 3 1
4.3 Hook shank machining
Figure 2 — Machined dimensions of shank
The length of the threaded portion of the shank shall be not less than 0,8 d .
) as follows:
The pitch of the thread (p) shall be proportioned to the principal diameter of the thread (d3
0,055 d ≤ p ≤ 0,15 d .
3 3
The depth of the thread (t) shall be proportioned to the pitch of the thread (p) as follows: 0,45 p ≤ t ≤ 0,61
p.
The bottom radius of the thread profile (r ) shall be no less than 0,14 p. A thread type, where the bottom
th
radius is not specified, shall not be used.
The shank shall be undercut (with a diameter d ) below the last threads for a length (s) proportioned to
the undercut depth as follows: s ≥ 2 (d − d ). The undercut shall reach deeper than the core diameter of
3 4
the thread profile (d ), in minimum as follows: d ≤ (d − 0,3 mm). The undercut shall be machined with
5 4 5
a form ground tool to a surface finish of Ra ≤ 6,3 µm.
There shall be a relief radius in a transition from the threaded part to the undercut part. The relief radius
(r ) shall be proportioned to the diameter of the undercut (d ) as follows: r ≥ 0,06 d . The shape of the
9 4 9 4
relief transition need not be a complete quadrant of a circle.
The thinnest section of the machined shank (consequently d ) shall fulfil the condition d ≥ 0,65 d , where
4 4 1
d is the diameter of the unmachined part of the shank, see Figure 1.
The whole machined section of the shank shall have a radius at each change in diameter. The machined
section shall not reach the curved part of the hook body.
Screwed threads shall conform to the tolerance requirements of ISO 965-1:2013 (coarse series) and be
of medium fit class 6g.
NOTE Annex F presents example sets of machined shank and thread dimensions, which fulfil the geometric
requirements.
4.4 Nut
The mechanical properties of the nut material shall be equal to or better than that required for the
material for hooks in accordance with 4.1. However, for standard metric nuts up to size M45 made of
materials in accordance with EN ISO 898-2:2022, from the material properties of the nut at least the yield
stress shall match or exceed the required yield stress of the hook material.
The height of the nut shall be such that the threaded length of the hook shank is fully engaged with the
nut thread.
The nut shall be positively locked to the shank against rotation to prevent the nut from unscrewing. The
locking shall not interfere with the lower two thirds of the nut/shank thread connection. The locking shall
allow relative axial movement between the shank and the nut due to play in the threaded connection.
Alternatively, if the nut is to be locked by a dowel or other similar fixing media, it is essential during the
locking process, the nut/shank load bearing thread flanks are in contact to avoid load transmission
through the locking media.
The support of the nut shall enable the hook to rotate about the vertical axis. The height position of the
contact surface shall fall
...