EN ISO 2320:2008

SLOVENSKI STANDARD
01-maj-2009
1DGRPHãþD
SIST EN ISO 2320:2001
SIST EN ISO 2320:2001/AC:2008
Jeklene samovarovalne matice - Mehanske in funkcionalne lastnosti (ISO
2320:2008)
Prevailing torque type steel nuts - Mechanical and performance properties (ISO
2320:2008)
Muttern aus Stahl mit Klemmteil - Mechanische und funktionelle Eigenschaften (ISO
2320:2008)
Écrous autofreinés en acier - Caractéristiques mécaniques et performances (ISO
2320:2008)
Ta slovenski standard je istoveten z: EN ISO 2320:2008
ICS:
21.060.20 Matice Nuts
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 2320
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2008
ICS 21.060.20 Supersedes EN ISO 2320:1997
English Version
Prevailing torque type steel nuts - Mechanical and performance
properties (ISO 2320:2008)
Écrous autofreinés en acier - Caractéristiques mécaniques Muttern aus Stahl mit Klemmteil - Mechanische und
et performances (ISO 2320:2008) funktionelle Eigenschaften (ISO 2320:2008)
This European Standard was approved by CEN on 25 October 2008.
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 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 Management Centre has the same status as the
official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2008 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 2320:2008: E
worldwide for CEN national Members.

Contents Page
Foreword.3

Foreword
This document (EN ISO 2320:2008) has been prepared by Technical Committee ISO/TC 2 "Fasteners" in
collaboration with Technical Committee CEN/TC 185 “Fasteners” the secretariat of which is held by DIN.
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 May 2009, and conflicting national standards shall be withdrawn at the
latest by May 2009.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 2320:1997.
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, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of ISO 2320:2008 has been approved by CEN as a EN ISO 2320:2008 without any modification.

INTERNATIONAL ISO
STANDARD 2320
Fourth edition
2008-11-01
Prevailing torque type steel nuts —
Mechanical and performance properties
Écrous autofreinés en acier — Caractéristiques mécaniques et
performances
Reference number
ISO 2320:2008(E)
©
ISO 2008
ISO 2320:2008(E)
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ii © ISO 2008 – All rights reserved

ISO 2320:2008(E)
Contents Page
Foreword. iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 2
4 Symbols . 2
5 Thread . 3
6 Lubrication . 3
7 Mechanical properties of prevailing torque type nuts. 3
8 Performance requirements for prevailing torque properties . 3
9 Test method. 12
9.1 General. 12
9.2 Proof load test. 12
9.3 Prevailing torque test . 12
Annex A (normative) Temperature resistance of prevailing torque non-metallic insert type nuts . 17
Annex B (informative) Basis for the evaluation of the total coefficient of friction, µ . 18
tot
Bibliography . 19

ISO 2320:2008(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.
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 2320 was prepared by Technical Committee ISO/TC 2, Fasteners, Subcommittee SC 1, Mechanical
properties of fasteners.
This fourth edition cancels and replaces the third edition (ISO 2320:1997), which has been technically revised.
It also incorporates the Technical Corrigendum ISO 2320:1997/Cor.1:2006.

iv © ISO 2008 – All rights reserved

INTERNATIONAL STANDARD ISO 2320:2008(E)

Prevailing torque type steel nuts — Mechanical and
performance properties
1 Scope
This International Standard specifies the mechanical and performance properties for prevailing torque type
steel nuts when tested at an ambient temperature range of +10 °C to +35 °C. It includes a single test to
determine the prevailing torque properties (performance properties) and/or the torque/clamp force properties.
This International Standard applies to prevailing torque all metal type nuts and prevailing torque non-metallic
insert type nuts:
a) with triangular ISO thread according to ISO 68-1;
b) with diameter/pitch combination according to ISO 261 and ISO 262;
c) with coarse pitch thread M3 to M39 and mechanical properties according to ISO 898-2;
d) with fine pitch thread M8×1 to M39×3 and mechanical properties according to ISO 898-6;
e) within the temperature range of −50 °C to +150 °C for prevailing torque all metal type nuts;
NOTE 1 See Clause 7, paragraph 3.
f) within the temperature range of −50 °C to +120 °C for prevailing torque non-metallic insert type nuts.
NOTE 2 See Clause 7, paragraph 4.
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 273:1979, Fasteners — Clearance holes for bolts and screws
ISO 898-1, Mechanical properties of fasteners made of carbon steel and alloy steel — Part 1: Bolts, screws
and studs
ISO 898-2, Mechanical properties of fasteners — Part 2: Nuts with specified proof load values — Coarse
thread
ISO 898-6, Mechanical properties of fasteners — Part 6: Nuts with specified proof load values — Fine pitch
thread
ISO 965-2, ISO general purpose metric screw threads — Tolerances — Part 2: Limits of sizes for general
purpose external and internal screw threads — Medium quality
ISO 16047, Fasteners — Torque/clamp force testing
ISO 2320:2008(E)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 16047 and the following apply.
3.1
prevailing torque type nut
nut which is not free-running on a mating thread by virtue of a self-contained prevailing torque feature, and
which provides a degree of resistance to rotation independent of clamping or compression forces
3.2
prevailing torque developed by the nut
torque necessary to rotate the nut on its mating externally threaded component and with no axial force in the
mating component
3.3
prevailing-on torque
torque to rotate the nut on its mating externally threaded component with the torque measured while the nut is
in motion and with no clamp force
3.4
prevailing-off torque
torque to rotate after backing off the nut until the removal of the clamp force in the externally threaded
component in the following 360° rotation of the nut
3.5
prevailing torque all metal type nut
nut which has a one piece or a multiple piece metal construction and derives its prevailing torque
characteristics from a controlled distortion of the nut thread and/or body or from metallic insert(s)
3.6
prevailing torque non-metallic insert type nut
nut which has a multiple piece construction and derives its prevailing torque characteristics from insert(s) of
non-metallic material located and retained in the nut
3.7
seating point
point in the tightening process where clamp force first appears
4 Symbols
For the purpose of this International Standard, the following symbols apply together with those defined in
ISO 16047.
Symbol Designation
d nominal diameter
d diameter of the hole of the fixture
F proof load
P
F lower load limit for the evaluation of the coefficient of total friction at 65 % of F
65 P
F upper load limit for the evaluation of the coefficient of total friction at 75 % of F
75 P
F test clamp force (shut-down force for the tightening process) at 80 % of F
80 P
P pitch of the thread
T prevailing-on torque, in newton metres
Fv
2 © ISO 2008 – All rights reserved

ISO 2320:2008(E)
T prevailing-off torque, in newton metres
Fd
T lower torque limit for the evaluation of the coefficient of total friction at F
65 65
T upper torque limit for the evaluation of the coefficient of total friction at F
75 75
T test torque corresponding to 80 % of the proof load, in newton metres (see Tables 1 to 8)
µ coefficient of total friction
tot
5 Thread
Threads for prevailing torque type nuts shall be in accordance with ISO 965-2 except for the prevailing torque
feature:
a) for prevailing torque non-metallic insert type nuts, the GO gauge shall be suitable for free installation (by
hand) until it is seated against the prevailing torque feature;
b) for prevailing torque all metal type nuts, the GO gauge shall be suitable for free installation (by hand) to
one pitch at least.
6 Lubrication
At the option of the manufacturer a lubricant may be applied to the manufacturing lot to fulfil the performance
requirements.
7 Mechanical properties of prevailing torque type nuts
The mechanical properties of prevailing torque type nuts shall conform to ISO 898-2 or ISO 898-6.
With regard to proof load, the test method specified in 9.2 shall apply.
For prevailing torque all metal type nuts, users should consult an experienced fastener materials expert for
temperatures outside the range of −50 °C to +150 °C to determine appropriate choices for a given application.
For prevailing torque non-metallic insert type nuts, use at or near the temperature limits of −50 °C and
+120 °C may reduce the prevailing torque capability and may require the use of an adequate non-metallic
material. Users should consult an experienced fastener materials expert for temperatures outside the range of
−50 °C to +120 °C to determine appropriate choices for a given application.
8 Performance requirements for prevailing torque properties
The prevailing-on torque shall not exceed the value specified for the applicable nut in Tables 1 to 8.
The prevailing-off torque shall exceed the value specified for the applicable nut in Tables 1 to 8.
For delivery inspection, the 1st installation/removal test applies, unless otherwise agreed.
For initial type testing and in case of dispute, a 5th removal test shall also be applied unless otherwise agreed.
Prevailing torque performance decreases as a function of the number of reuses; the consumer should take
into consideration the consequences of the decreased performance before any reuse of the nut.
By request of the customer, a temperature resistance test for prevailing torque non-metallic insert type nuts as
given in Annex A may be carried out.
Paragraphs 3 and 4 of Clause 7 also apply to performance requirements.
ISO 2320:2008(E)
Table 1 — Test clamp force and prevailing torques for prevailing torque type nuts of property class 04
Clamp force for evaluation
Prevailing torque
of total friction coefficient
Test clamp
N⋅m
b
force
µ
Thread
tot
a
F
Upper limit Lower limit
d P 80
1st installation 1st removal 5th removal
c d
N
F F
75 65
e f f
T T T
Fv,max Fd,min Fd,min
N N
M3 1 528 1 433 1 242 0,43 0,12 0,08
M4 2 672 2 505 2 171 0,9 0,18 0,12
M5 4 320 4 050 3 510 1,6 0,29 0,2
M6 6 112 5 730 4 966 3 0,45 0,3
M7 8 800 8 250 7 150 4,5 0,65 0,45
M8 11 120 10 425 9 035
6 0,85 0,6
M8×1 11 920 11 175 9 685
M10 17 600 16 500 14 300
10,5 1,5 1
M10×1,25 18 640 17 475 15 145
M10×1 19 600 18 375 15 925
M12 25 600 24 000 20 800
15,5 2,3 1,6
M12×1,5 26 800 25 125 21 775
M12×1,25 28 000 26 250 22 750
M14 34 960 32 775 28 405
24 3,3 2,3
M14×1,5 38 000 35 625 30 875
M16 47 760 44 775 38 805
32 4,5 3
M16×1,5 50 800 47 625 41 275
M18 58 400 54 750 47 450
42 6 4,2
M18×1,5 65 360 61 275 53 105
M20 74 480 69 825 60 515
54 7,5 5,3
M20×1,5 82 720 77 550 67 210
M22 92 080 86 325 74 815
68 9,5 6,5
M22×1,5 101 200 94 875 82 225
M24 107 280 100 575 87 165
80 11,5 8
M24×2 116 720 109 425 94 835
M27 139 520 130 800 113 360
94 13,5 10
M27×2 150 800 141 375 122 525
M30 170 560 159 900 138 580
108 16 12
M30×2 188 800 177 000 153 400
M33 210 960 197 775 171 405
122 18 14
M33×2 231 360 216 900 187 980
M36 248 400 232 875 201 825
136 21 16
M36×3 262 960 246 525 213 655
M39 296 720 278 175 241 085
150 23 18
M39×3 313 120 293 550 254 410
NOTE The evaluation of results from the prevailing torque test by statistical process control methods (SPC) has no statistical relevance.
a
The clamp force for property class 04 nuts is equal to 80 % of the proof load of property class 04 nuts for 3 mm u d u 39 mm. Proof loads for nuts

are given in ISO 898-2 and ISO 898-6.
b
See Annex B.
c
The value of the upper limit of the clamp force is equal to 75 % of the proof load, see Annex B.
d
The value of the lower limit of the clamp force is equal to 65 % of the proof load, see Annex B.
e
The prevailing torques for first assembly apply for all metal type nuts only. For prevailing torque non-metallic insert type nuts, the maximum torques
shall be 50 % of the values.
f
Values in this table are required for testing performed under laboratory acceptance test conditions. Utilization of this type of fastener is application
dependent and performance for parts may vary in normal use. It is recommended that additional testing of complete joints, using production components,
be performed when there are questions of product performance.
4 © ISO 2008 – All rights reserved

ISO 2320:2008(E)
Table 2 — Test clamp force and prevailing torques for prevailing torque type nuts of property class 05
Clamp force for evaluation
Prevailing torque
of total friction coefficient
Test clamp
N⋅m
b
force
µ
tot
Thread
a
F
Upper limit Lower limit
d P
1st installation 1st removal 5th removal
c d
N F F
75 65
e f f
T T T
Fv,max Fd,min Fd,min
N N
M3 2 000 1 875 1 625 0,6 0,15 0,1
M4 3 520 3 300 2 860 1,2 0,22 0,15
M5 5 680 5 325 4 615 2,1 0,35 0,24
M6 8 000 7 500 6 500 4 0,55 0,4
M7 11 600 10 875 9 425 6 0,85 0,6
M8 14 640 13 725 11 895
8 1,15 0,8
M8×1 15 680 14 700 12 740
M10 23 200 21 750 18 850
14 2 1,4
M10×1,25 24 480 22 950 19 890
M10×1 25 760 24 150 20 930
M12 33 760 31 650 27 430
M12×1,5 35 200 33 000 28 600 21 3,1 2,1
M12×1,25 36 800 34 500 29 900
M14 46 000 43 125 37 375
31 4,4 3
M14×1,5 50 000 46 875 40 625
M16 62 800 58 875 51 025
42 6 4,2
M16×1,5 66 800 62 625 54 275
M18 76 800 72 000 62 400
56 8 5,5
M18×1,5 86 000 80 625 69 875
M20 98 000 91 875 79 625
72 10,5 7
M20×1,5 108 800 102 000 88 400
M22 121 200 113 625 98 475
90 13 9
M22×1,5 133 200 124 875 108 225
M24 141 200 132 375 114 725
106 15 10,5
M24×2 153 600 144 000 124 800
M27 183 600 172 125 149 175
123 17 12
M27×2 198 400 186 000 161 200
M30 224 400 210 375 182 325
140 19 14
M30×2 248 400 232 875 201 825
M33 277 600 260 250 225 550
160 21,5 15,5
M33×2 304 400 285 375 247 325
M36 326 800 306 375 265 525
180 24 17,5
M36×3 346 000 324 375 281 125
M39 390 400 366 000 317 200
200 26,5 19,5
M39×3 412 000 386 250 334 750
NOTE The evaluation of results from the prevailing torque test by statistical process control methods (SPC) has no statistical relevance.
a
The clamp force for property class 05 nuts is equal to 80 % of the proof load of property class 05 nuts for 3 mm u d u 39 mm. Proof loads for nuts

are given in ISO 898-2 and ISO 898-6.
b
See Annex B.
c
The value of the upper limit of the clamp force is equal to 75 % of the proof load, see Annex B.
d
The value of the lower limit of the clamp force is equal to 65 % of the proof load, see Annex B.
e
The prevailing torques for first assembly apply for all metal type nuts only. For prevailing torque non-metallic insert type nuts, the maximum torques
shall be 50 % of the values.
f
Values in this table are required for testing performed under laboratory acceptance test conditions. Utilization of this type of fastener is application
dependent and performance for parts may vary in normal use. It is recommended that additional testing of complete joints, using production components,
be performed when there are questions of product performance.

ISO 2320:2008(E)
Table 3 — Test clamp force and prevailing torques for prevailing torque type nuts of property class 5
Clamp force for evaluation
Prevailing torque
of total friction coefficient
Test clamp
N⋅m
b
force
µ
tot
Thread
a
F
Upper limit Lower limit
d P
1st installation 1st removal 5th removal
c d
N
F F
75 65
e f f
T T T
Fv,max Fd,min Fd,min
N N
M3 1 528 1 433 1 242 0,43 0,12 0,08
M4 2 672 2 505 2 171 0,9 0,18 0,12
M5 4 320 4 050 3 510 1,6 0,29 0,2
M6 6 112 5 730 4 966 3 0,45 0,3
M7 8 800 8 250 7 150 4,5 0,65 0,45
M8 11 120 10 425 9 035
6 0,85 0,6
M8×1 11 920 11 175 9 685
M10 17 600 16 500 14 300
10,5 1,5 1
M10×1,25 18 640 17 475 15 145
M10×1 19 600 18 375 15 925
M12 25 600 24 000 20 800
M12×1,5 26 800 25 125 21 775 15,5 2,3 1,6
M12×1,25 28 000 26 250 22 750
M14 34 960 32 775 28 405
24 3,3 2,3
M14×1,5 38 000 35 625 30 875
M16 47 760 44 775 38 805
32 4,5 3
M16×1,5 50 800 47 625 41 275
M18 58 400 54 750 47 450
42 6 4,2
M18×1,5 65 680 61 575 53 365
M20 74 480 69 825 60 515
54 7,5 5,3
M20×1,5 82 400 77 250 66 950
M22 92 000 86 250 74 750
68 9,5 6,5
M22×1,5 100 800 94 500 81 900
M24 107 200 100 500 87 100
80 11,5 8
M24×2 116 800 109 500 94 900
M27
...