EN ISO 6508-1:2023

SLOVENSKI STANDARD
01-april-2024
Kovinski materiali - Preskus trdote po Rockwellu - 1. del: Preskusna metoda (ISO
6508-1:2023)
Metallic materials - Rockwell hardness test - Part 1: Test method (ISO 6508-1:2023)
Metallische Werkstoffe - Härteprüfung nach Rockwell - Teil 1: Prüfverfahren (ISO 6508-
1:2023)
Matériaux métalliques - Essai de dureté Rockwell - Partie 1: Méthode d'essai (ISO 6508-
1:2023)
Ta slovenski standard je istoveten z: EN ISO 6508-1:2023
ICS:
77.040.10 Mehansko preskušanje kovin Mechanical testing of metals
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 6508-1
EUROPEAN STANDARD
NORME EUROPÉENNE
December 2023
EUROPÄISCHE NORM
ICS 77.040.10 Supersedes EN ISO 6508-1:2016
English Version
Metallic materials - Rockwell hardness test - Part 1: Test
method (ISO 6508-1:2023)
Matériaux métalliques - Essai de dureté Rockwell - Metallische Werkstoffe - Härteprüfung nach Rockwell -
Partie 1: Méthode d'essai (ISO 6508-1:2023) Teil 1: Prüfverfahren (ISO 6508-1:2023)
This European Standard was approved by CEN on 13 November 2023.

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
© 2023 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 6508-1:2023 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 6508-1:2023) has been prepared by Technical Committee ISO/TC 164
"Mechanical testing of metals" in collaboration with Technical Committee CEN/TC 459/SC 1 “Test
methods for steel (other than chemical analysis)” the secretariat of which is held by AFNOR.
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 2024, and conflicting national standards shall be
withdrawn at the latest by June 2024.
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 ISO 6508-1:2016.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. 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.
Endorsement notice
The text of ISO 6508-1:2023 has been approved by CEN as EN ISO 6508-1:2023 without any
modification.
INTERNATIONAL ISO
STANDARD 6508-1
Fifth edition
2023-12
Metallic materials — Rockwell
hardness test —
Part 1:
Test method
Matériaux métalliques — Essai de dureté Rockwell —
Partie 1: Méthode d'essai
Reference number
ISO 6508-1:2023(E)
ISO 6508-1:2023(E)
© ISO 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 6508-1:2023(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols, abbreviated terms and designations . 1
5 Rockwell hardness . .3
6 Testing machine.4
7 Test piece . 5
8 Procedure .5
9 Uncertainty of the results . 7
10 Test report . 7
11 Conversions to other hardness scales or tensile strength values .8
Annex A (normative) Special HR30TSm and HR15TSm test for thin products .9
Annex B (normative) Minimum thickness of the test piece in relation to the Rockwell
hardness .10
Annex C (normative) Corrections to be added to Rockwell hardness values obtained on
convex cylindrical surfaces .13
Annex D (normative) Corrections to be added to Rockwell hardness C scale values obtained
on spherical test surfaces of various diameters .16
Annex E (normative) Daily verification procedure .17
Annex F (normative) Inspection of diamond indenters .20
Annex G (informative) Uncertainty of the measured hardness values .21
Annex H (informative) CCM — Working group on hardness .26
Annex I (informative) Rockwell hardness measurement traceability .27
Bibliography .31
iii
ISO 6508-1:2023(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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use
of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed
patent rights in respect thereof. As of the date of publication of this document, ISO had not received
notice of (a) patent(s) which may be required to implement this document. However, implementers are
cautioned that this may not represent the latest information, which may be obtained from the patent
database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all
such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
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 164, Mechanical testing of metals,
Subcommittee SC 3, Hardness testing, in collaboration with the European Committee for Standardization
(CEN) Technical Committee CEN/TC 459, ECISS - European Committee for Iron and Steel Standardization,
in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This fifth edition cancels and replaces the fourth edition (ISO 6508-1:2016), which has been technically
revised.
The main changes are as follows:
— removal of note related to the use of tungsten and steel ball indenters (Clause 1);
— removal of the year from the Normative References specified and various places throughout the
body of the standard (Clause 2);
— addition of Clause 3, Terms and definitions;
— added additional information for the use of single-piece spherically tipped indenters (6.3 NOTE 1);
— added the table reference and table title (7.4);
— modified the uncertainty of the results section to only provide a single reference for the determination
of uncertainty (Clause 9);
— modified Annex G to remove the “procedure without bias (M2)” method for determining uncertainty.
A list of all parts in the ISO 6508 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.
iv
INTERNATIONAL STANDARD ISO 6508-1:2023(E)
Metallic materials — Rockwell hardness test —
Part 1:
Test method
1 Scope
This document specifies the method for Rockwell regular and Rockwell superficial hardness tests for
scales A, B, C, D, E, F, G, H, K, 15N, 30N, 45N, 15T, 30T, and 45T for metallic materials and is applicable to
stationary and portable hardness testing machines.
For specific materials and/or products, other specific International Standards apply (e.g. ISO 3738-1
and ISO 4498).
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 6508-2, Metallic materials — Rockwell hardness test — Part 2: Verification and calibration of testing
machines and indenters
ISO 6508-3, Metallic materials — Rockwell hardness test — Part 3: Calibration of reference blocks
3 Terms and definitions
No terms and definitions are listed in this document.
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/
4 Symbols, abbreviated terms and designations
According to Table 1, Table 2, Table 3, and Figure 1.
ISO 6508-1:2023(E)
Table 1 — Rockwell regular scales
Rockwell Hardness Type of indenter Preliminary Total Scaling Full Applicable
symbol force force constant range range
regular
of application
hardness Unit F F S constant
(Rockwell
scale
N
regular
hardness scales)
A HRA Diamond cone 98,07 N 588,4 N 0,002 mm 100 20 HRA to
95 HRA
B HRBW Ball 1,587 5 mm 98,07 N 980,7 N 0,002 mm 130 10 HRBW to
100 HRBW
a
C HRC Diamond cone 98,07 N 1,471 kN 0,002 mm 100 20 HRC to
70 HRC
D HRD Diamond cone 98,07 N 980,7 N 0,002 mm 100 40 HRD to
77 HRD
E HREW Ball 3,175 mm 98,07 N 980,7 N 0,002 mm 130 70 HREW to
100 HREW
F HRFW Ball 1,587 5 mm 98,07 N 588,4 N 0,002 mm 130 60 HRFW to
100 HRFW
G HRGW Ball 1,587 5 mm 98,07 N 1,471 kN 0,002 mm 130 30 HRGW to
94 HRGW
H HRHW Ball 3,175 mm 98,07 N 588,4 N 0,002 mm 130 80 HRHW to
100 HRHW
K HRKW Ball 3,175 mm 98,07 N 1,471 kN 0,002 mm 130 40 HRKW to
100 HRKW
a
The applicable range of application can be extended to 10 HRC if the surfaces of the diamond cone and spherical tip are
polished for a penetration depth of at least 0,4 mm.
Table 2 — Rockwell superficial scales
Rockwell Hardness Type of Preliminary Total Scaling Full Applicable
superficial symbol indenter force force constant range range
hardness constant of application
Unit F F S
scale (Rockwell
N
superficial
hardness scales)
15N HR15N Diamond cone 29,42 N 147,1 N 0,001 mm 100 70 HR15N to
94 HR15N
30N HR30N Diamond cone 29,42 N 294,2 N 0,001 mm 100 42 HR30N to
86 HR30N
45N HR45N Diamond cone 29,42 N 441,3 N 0,001 mm 100 20 HR45N to
77 HR45N
15T HR15TW Ball 1,587 5 mm 29,42 N 147,1 N 0,001 mm 100 67 HR15TW to
93 HR15TW
30T HR30TW Ball 1,587 5 mm 29,42 N 294,2 N 0,001 mm 100 29 HR30TW to
82 HR30TW
45T HR45TW Ball 1,587 5 mm 29,42 N 441,3 N 0,001 mm 100 10 HR45TW to
72 HR45TW
Scales using indenter balls with diameter 6,350 mm and 12,70 mm may also be used, if specified in the
[5]
product specification or by special agreement. See ASTM E18 for additional scales using these ball
sizes.
NOTE 1 For certain materials, it is possible that the applicable range of application is narrower than those
indicated.
ISO 6508-1:2023(E)
NOTE 2 The numbers representing the test forces were originally based on units of kgf. For example, the total
test force of 30 kgf has been converted to 294,2 N.
Table 3 — Symbols and abbreviated terms
Symbol/
abbreviated Definition Unit
term
F Preliminary test force N
F Additional test force (total force minus preliminary force) N
F Total test force N
S Scaling constant, specific to the scale mm
N Full range constant, specific to the scale -
h Permanent depth of indentation under preliminary test force after removal of mm
additional test force (permanent indentation depth)
HRA
h
HRC Rockwell regular hardness =100−
0,002
HRD
HRBW
HREW
HRFW h
Rockwell regular hardness =130−
HRGW
0,002
HRHW
HRKW
HRN
h
Rockwell superficial hardness =100−
HRTW
0,001
5 Rockwell hardness
5.1 The following is an example of the designation of Rockwell hardness.
EXAMPLE 70 HR30TW, where:
NOTE 1 Previous versions of this document allowed the use of steel indenter balls, which required the suffix S.
NOTE 2 For the HR30TSm and HR15TSm scales specified in Annex A, a capital S and a lower-case m are used
indicating the use of steel indenter balls and a diamond spot specimen holder.
ISO 6508-1:2023(E)
Key
X time 4 permanent indentation depth, h
Y indenter position 5 surface of specimen
1 indentation depth by preliminary force, F 6 reference plane for measurement
2 indentation depth by additional test force, F 7 position of indenter
3 elastic recovery just after removal of additional test force, F 8 indentation depth vs. time curve
Figure 1 — Rockwell principle diagram
5.2 Principle:
An indenter of specified size, shape and material is forced into the surface of a test specimen under two
force levels using the specific conditions specified in Clause 8. The specified preliminary force is applied
and the initial indentation depth is measured, followed by the application and removal of a specified
additional force, returning to the preliminary force. The final indentation depth is then measured and
the Rockwell hardness value (H) is derived from the difference, h, in the final and initial indentation
depths and the two constants N and S (see Figure 1, Table 1, and Table 2) as shown in Formula (1):
h
HN=− (1)
S
6 Testing machine
6.1 Testing machine, shall be capable of applying the test forces for some or all of the Rockwell
hardness scales as shown in Table 1 and Table 2, performing the procedure specified in Clause 8, and
complying with all of the requirements specified in ISO 6508-2.
6.2 Spheroconical diamond indenter, shall be in accordance with ISO 6508-2, with an included
angle of 120° and radius of curvature at the tip of 0,2 mm. Diamond indenters shall be certified for use
for either:
— only the regular Rockwell diamond scales,
— only the superficial Rockwell diamond scales, or
ISO 6508-1:2023(E)
— both the regular and the superficial Rockwell diamond scales.
6.3 Ball indenter, shall be tungsten carbide composite in accordance with ISO 6508-2, with a
diameter of 1,587 5 mm or 3,175 mm (see NOTE 1 and NOTE 2).
NOTE 1 Ball indenters normally consist of a spherical ball and a separate appropriately designed holder. Single-
piece spherically tipped indenters are allowed, provided that the surface of the indenter that makes contact with
the test piece meets the size, shape, finish, and hardness requirements for the calibration and verification of the
ball indenter as specified in ISO 6508-2, and meets the performance requirements for the indirect verification of
the ball holder assembly as specified in ISO 6508-2.
NOTE 2 Attention is drawn to the fact that the use of tungsten carbide composite for ball indenters is the
standard type of Rockwell indenter ball. Steel indenter balls can only be used when performing Rockwell
HR30TSm and HR15TSm tests according to Annex A.
7 Test piece
7.1 The test shall be carried out on a surface which is smooth and even, free from oxide scale, foreign
matter and, in particular, completely free from lubricants, unless specified otherwise in product or
materials standards.
An exception is made for reactive metals, such as titanium, which might adhere to the indenter. In such
situations, a suitable lubricant such as kerosene may be used. The use of a lubricant shall be reported on
the test report.
7.2 Preparation shall be carried out in such a way that any alteration of the surface hardness due to
excessive heating or cold-working for example, is minimized.
This shall be taken into account, particularly in the case of low-depth indentations.
7.3 The thickness of the test piece, or of the layer under test (minimum values are given in Annex B),
shall be at least 10 times the permanent indentation depth for diamond indenters and 15 times the
permanent indentation depth for ball indenters, unless it can be demonstrated that the use of a thinner
test piece does not affect the measured hardness value.
In general, no deformation should be visible on the back of the test piece after the test, although not all
such marking is indicative of a bad test.
Follow Annex A for special requirements for testing very thin sheet metal using the HR30TSm and
HR15TSm scales.
7.4 For tests on convex cylindrical surfaces and spherical surfaces, see 8.11.
8 Procedure
8.1 This document has been developed with a laboratory temperature requirement of 10 °C to 35 °C.
For environments outside the stated requirement, it is the responsibility of the testing laboratory to
assess the impact on testing data produced with testing machines operated in such environments. When
testing is performed outside the recommended temperature limits of 10 °C to 35 °C, the temperature
shall be recorded and reported.
NOTE If significant temperature gradients are present during testing and/or calibration, measurement
uncertainty can increase and out of tolerance conditions can occur.
ISO 6508-1:2023(E)
8.2 The daily verification specified in Annex E shall be performed before the first test of each day for
each scale to be used.
The condition of diamond indenters should be checked according to Annex F.
8.3 After each change, or removal and replacement, of the indenter, indenter ball, or test piece
support, perform at least two tests and discard the results, then determine that the indenter and the
test piece support are correctly mounted in the machine by performing the daily verification process
specified in Annex E.
8.4 The diamond or ball indenter shall have been the indenter used during the last indirect
verification.
If the indenter was not used during the indirect verification and is being used for the first time, it shall
be verified in accordance with the daily verification given in Annex E using at least two test blocks (one
from the low and high ranges as specified by ISO 6508-2:2023, Table 1) for each Rockwell scale that is
normally used. This does not apply to replacing a ball.
8.5 The test piece shall be placed on a rigid support and supported in such a manner that the surface
to be indented is in a plane normal to the axis of the indenter and the line of the indenting force, as well
as to avoid a displacement of the test piece.
Products of cylindrical shape shall be suitably supported, for example, on centring V-block or double
cylinders made of material with a Rockwell hardness of at least 60 HRC. Special attention shall be given
to the correct seating, bearing, and alignment of the indenters, the test piece, the centring V-blocks,
and the specimen holder of the testing machine, since any perpendicular misalignment might result in
incorrect results.
8.6 Bring the indenter into contact with the test surface and apply the preliminary test force, F ,
without shock, vibration, oscillation, or overload.
The preliminary force application time should not exceed 2 s. The duration of the preliminary test force,
+1
F , shall be 3 s.
−2
NOTE The requirements for the time durations are given with asymmetric limits.
+1
EXAMPLE 3 s indicates that 3 s is the ideal time duration, with an acceptable range of not less than
−2
1 s (3 s - 2 s) to not more than 4 s (3 s + 1 s).
8.7 Measure the initial indentation depth.
For many manual (dial-indicator) machines, this is done by setting the indicating dial to its set-point or
zero position. For many automatic (digital) machines, the depth measurement is made automatically
without the user’s input and might not be displayed.
8.8 Apply the additional force F without shock, vibration, oscillation, or overload to increase the
force from F to the total force, F.
For the regular Rockwell scale tests, apply the additional test force, F , in not less than 1 s and not more
than 8 s. For all HRN and HRTW Rockwell superficial test scales, apply the additional test force, F , in
less than or equal to 4 s.
It is recommended to perform the same test cycle used during indirect verification.
NOTE There is evidence that some materials are sensitive to the rate of straining which causes small changes
in the value of the yield stress. The corresponding effect on the termination of the formation of an indentation
can make an alteration in the hardness value.
ISO 6508-1:2023(E)
+1
8.9 The total test force, F, shall be maintained for a duration of 5 s. Remove the additional test
−3
+1
force, F , and, while the preliminary test force, F , is maintained, after 4 s, the final reading shall be
1 0
−3
made.
As an exception for test materials exhibiting excessive plastic flow (indentation creep) during the
application of the total test force, special considerations can be necessary since the indenter will
continue to penetrate. When materials require the use of a total force duration that exceeds the 6 s
allowed by the tolerances, the actual extended total force duration used shall be reported following the
test results (for example, 65 HRF/10 s).
8.10 Measure the final indentation depth while the preliminary test force is applied.
The Rockwell hardness number is calculated from the permanent indentation depth, h, using the
formula given in Formula (1) and the information given in Table 1, Table 2, and Table 3. For most
Rockwell hardness machines, the depth measurement is made in a manner that automatically calculates
and displays the Rockwell hardness number.
The derivation of the Rockwell hardness number is illustrated in Figure 1.
8.11 For tests on convex cylindrical surfaces and spherical surfaces, the corrections given in Annex C
(Table C.1, Table C.2, Table C.3, or Table C.4) and in Annex D (Table D.1) shall be applied.
The correction values shall be reported on the test report.
In the absence of corrections for tests on concave surfaces, tests on such surfaces should be the subject
of special agreement.
8.12 Throughout the test, the apparatus shall be protected from shock or vibration.
8.13 The distance between the centres of two adjacent indentations shall be at least three times the
diameter of the indentation. The distance from the centre of any indentation to an edge of the test piece
shall be at least two and a half times the diameter of the indentation.
9 Uncertainty of the results
A complete evaluation of the uncertainty should be done according to ISO/IEC Guide 98-3.
A guideline for the determination is given in Annex G.
10 Test report
The laboratory shall record at least the following information and that information shall be included in
the test report, unless agreed by the parties concerned:
a) a reference to this document, i.e. ISO 6508-1:2023;
b) all details necessary for the complete identification of the test piece, including the curvature of the
test surface;
c) the test temperature, if it is not within the limits of 10 °C to 35 °C;
d) the hardness result in the format specified in 5.2;
e) all operations not specified in this document, or regarded as optional;
f) details of any occurrence which may have possibly affected the result;
ISO 6508-1:2023(E)
g) the actual extended total force duration time used, if greater than the 6 s allowed by the tolerances;
h) the date the test was performed;
i) if conversion to another hardness scale is also performed, the basis and method of this conversion
shall be specified (see ISO 18265).
11 Conversions to other hardness scales or tensile strength values
There is no general process for accurately converting Rockwell hardness into other scales, or hardness
into tensile strength. Such conversions, therefore, should be avoided, unless a reliable basis for
conversion can be obtained by comparison tests (see also ISO 18265).
ISO 6508-1:2023(E)
Annex A
(normative)
Special HR30TSm and HR15TSm test for thin products
A.1 General
This test is applicable to thin sheet metal products having a maximum thickness of 0,6 mm to the
minimum thickness indicated in the product standards, and of a maximum hardness of 82 HR30TSm
or 93 HR15TSm. The product standard shall specify when the Special HR30TSm or HR15TSm hardness
test is to be applied.
This test is carried out under conditions similar to those in the HR30TW or HR15TW test specified
in this document. The appearance of deformation on the bottom of the test pieces below the indent is
permitted. Prior to testing, hardness tests should be made on thin sheet samples of a known hardness
to verify that the specimen holder surface does not affect the measurement results.
NOTE 1 The Sm in the scale designations indicates that a steel ball indenter and a diamond spot specimen
holder are used for this testing.
The following requirements shall be met, in addition to those specified in this document.
A.2 Ball indenter
A hardened steel ball indenter, that meets the requirements of ISO 6508-2, with a diameter of
1,587 5 mm shall be used for this testing.
A.3 Test piece support
The test piece support shall comprise a polished and smooth flat diamond surface approximately
4,5 mm in diameter. This support surface shall be approximately centred on the axis of the indenter
and shall be perpendicular to it. Care shall be taken to ensure that it is seated correctly on the machine
table.
A.4 Test piece preparation
If it is necessary to remove material from the test piece, this should be done on both sides of the test
piece. Care shall be taken to ensure that this process does not change the condition of the base metal,
for example, by heating or work hardening. The base metal shall not be made thinner than the minimum
allowable thickness.
A.5 Position of the test piece
The distance between the centres of two adjacent indentations or between the centre of one of the
indentations and the edge of the test piece shall be at least 5 mm, unless otherwise specified.
ISO 6508-1:2023(E)
Annex B
(normative)
Minimum thickness of the test piece in relation to the Rockwell
hardness
The minimum thickness of the test piece, or of the layer under test, is given in Figure B.1, Figure B.2,
and Figure B.3.
Key
X Rockwell hardness
Y minimum thickness of the test piece, mm
Figure B.1 — Test with diamond cone indenter (scales A, C, and D)
ISO 6508-1:2023(E)
Key
X Rockwell hardness
Y minimum thickness of the test piece, mm
Figure B.2 — Test with ball indenter (scales B, E, F, G, H, and K)
ISO 6508-1:2023(E)
Key
X Rockwell hardness
Y minimum thickness of the test piece, mm
Figure B.3 — Rockwell superficial test (scales N and T)
ISO 6508-1:2023(E)
Annex C
(normative)
Corrections to be added to Rockwell hardness values obtained on
convex cylindrical surfaces
For tests on convex cylindrical surfaces, the corrections given in Table C.1, Table C.2, Table C.3, or
Table C.4 shall be applied. For radii other than those given in these tables, corrections may be derived
by linear interpolation.
Table C.1 — Test with diamond cone indenter (scales A, C, and D)
Rockwell Radius of curvature
hardness
mm
reading
3 5 6,5 8 9,5 11 12,5 16 19
20 - - - 2,5 2,0 1,5 1,5 1,0 1,0
25 - - 3,0 2,5 2,0 1,5 1,0 1,0 1,0
30 - - 2,5 2,0 1,5 1,5 1,0 1,0 0,5
35 - 3,0 2,0 1,5 1,5 1,0 1,0 0,5 0,5
40 - 2,5 2,0 1,5 1,0 1,0 1,0 0,5 0,5
45 3,0 2,0 1,5 1,0 1,0 1,0 0,5 0,5 0,5
50 2,5 2,0 1,5 1,0 1,0 0,5 0,5 0,5 0,5
55 2,0 1,5 1,0 1,0 0,5 0,5 0,5 0,5 0
60 1,5 1,0 1,0 0,5 0,5 0,5 0,5 0 0
65 1,5 1,0 1,0 0,5 0,5 0,5 0,5 0 0
70 1,0 1,0 0,5 0,5 0,5 0,5 0,5 0 0
75 1,0 0,5 0,5 0,5 0,5 0,5 0 0 0
80 0,5 0,5 0,5 0,5 0,5 0 0 0 0
85 0,5 0,5 0,5 0 0 0 0 0 0
90 0,5 0 0 0 0 0 0 0 0
NOTE Corrections greater than 3 HRA, 3 HRC, and 3 HRD are not considered acceptable and are therefore not included in
this table.
Table C.2 — Tests with 1,587 5 mm ball indenter (scales B, F, and G)
Rockwell Radius of curvature
hardness
mm
reading
3 5 6,5 8 9,5 11 12,5
20 - - - 4,5 4,0 3,5 3,0
30 - - 5,0 4,5 3,5 3,0 2,5
40 - - 4,5 4,0 3,0 2,5 2,5
50 - - 4,0 3,5 3,0 2,5 2,0
60 - 5,0 3,5 3,0 2,5 2,0 2,0
70 - 4,0 3,0 2,5 2,0 2,0 1,5
NOTE Corrections greater than 5 HRB, 5 HRF, and 5 HRG are not considered acceptable and are therefore not included in
this table.
ISO 6508-1:2023(E)
TTabablele C C.22 ((ccoonnttiinnueuedd))
Rockwell Radius of curvature
hardness
mm
reading
3 5 6,5 8 9,5 11 12,5
80 5,0 3,5 2,5 2,0 1,5 1,5 1,5
90 4,0 3,0 2,0 1,5 1,5 1,5 1,0
100 3,5 2,5 1,5 1,5 1,0 1,0 0,5
NOTE Corrections greater than 5 HRB, 5 HRF, and 5 HRG are not considered acceptable and are therefore not included in
this table.
a, b
Table C.3 — Rockwell superficial test (scales 15N, 30N, 45N)
Rockwell Radius of curvature
superficial
mm
hardness
1,6 3,2 5 6,5 9,5 12,5
reading
c
20 (6,0) 3,0 2,0 1,5 1,5 1,5
c
25 (5,5) 3,0 2,0 1,5 1,5 1,0
c
30 (5,5) 3,0 2,0 1,5 1,0 1,0
c
35 (5,0) 2,5 2,0 1,5 1,0 1,0
c
40 (4,5) 2,5 1,5 1,5 1,0 1,0
c
45 (4,0) 2,0 1,5 1,0 1,0 1,0
c
50 (3,5) 2,0 1,5 1,0 1,0 1,0
c
55 (3,5) 2,0 1,5 1,0 0,5 0,5
60 3,0 1,5 1,0 1,0 0,5 0,5
65 2,5 1,5 1,0 0,5 0,5 0,5
70 2,0 1,0 1,0 0,5 0,5 0,5
75 1,5 1,0 0,5 0,5 0,5 0
80 1,0 0,5 0,5 0,5 0 0
85 0,5 0,5 0,5 0,5 0 0
90 0 0 0 0 0 0
a
These corrections are approximate only and represent the averages, to the nearest 0,5 Rockwell superficial hardness
units, of numerous actual observations of the test surfaces having the curvatures given in this table.
b
When testing convex cylindrical surfaces, the accuracy of the test will be seriously affected by misalignment of the
elevating screw, V- specimen holder and indenter and by imperfections in the surface finish and straightness of the cylinder.
c
The corrections given in parentheses shall not be used, except by agreement.
ISO 6508-1:2023(E)
a, b
Table C.4 — Rockwell superficial test (scales 15T, 30T, 45T)
Rockwell Radius of curvature
superficial
mm
hardness
1,6 3,2 5 6,5 8 9,5 12,5
reading
c c c c c
20 (13) (9,0) (6,0) (4,5) (3,5) 3,0 2,0
c c c c c
30 (11,5) (7,5) (5,0) (4,0) (3,5) 2,5 2,0
c c c c
40 (10,0) (6,5) (4,5) (3,5) 3,0 2,5 2,0
c c c
50 (8,5) (5,5) (4,0) 3,0 2,5 2,0 1,5
c c
60 (6,5) (4,5) 3,0 2,5 2,0 1,5 1,5
c c
70 (5,0) (3,5) 2,5 2,0 1,5 1,0 1,0
80 3,0 2,0 1,5 1,5 1,0 1,0 0,5
90 1,5 1,0 1,0 0,5 0,5 0,5 0,5
a
These corrections are approximate only and represent the averages, to the nearest 0,5 Rockwell superficial hardness
units, of numerous actual observations of the test surfaces having the curvatures given in this table.
b
When testing convex cylindrical surfaces, the accuracy of the test will be seriously affected by misalignment of the
elevating screw, V- specimen holder and indenter and by imperfections in the surface finish and straightness of the cylinder.
c
The corrections given in parentheses shall not be used, except by agreement.
ISO 6508-1:2023(E)
Annex D
(normative)
Corrections to be added to Rockwell hardness C scale values
obtained on spherical test surfaces of various diameters
For tests on convex spherical surfaces, the corrections given in Table D.1 shall be applied.
Table D.1 — Correction values to be added to Rockwell hardness C scale values
Rockwell Diameter of sphere
hardness d
reading mm
4 6,5 8 9,5 11 12,5 15 20 25
55 HRC 6,4 3,9 3,2 2,7 2,3 2,0 1,7 1,3 1,0
60 HRC 5,8 3,6 2,9 2,4 2,1 1,8 1,5 1,2 0,9
65 HRC 5,2 3,2 2,6 2,2 1,9 1,7 1,4 1,0 0,8
The values of the correction to be added to Rockwell hardness C scale ΔH, given in Table D.1, are
calculated using Formula (D.1):
H
 
1−
 
 
ΔH =× (D.1)
d
where
H is the Rockwell hardness reading;
d is the diameter of the sphere, expressed in millimetres.
ISO 6508-1:2023(E)
Annex E
(normative)
Daily verification procedure
E.1 General
A daily verification of the machine shall be carried out on each day that the machine is used by performing
tests in each hardness scale that is to be used that day. Select at least one hardness reference block that
meets the requirements of ISO 6508-3 from the ranges specified in Table E.1. It is recommended that
the hardness level selected be close to the levels to be tested. Only the calibrated surface of the test
blocks are to be used for testing. Perform at least two indentations on each block and calculate the bias
and repeatability range of the results using the formulae specified below. If the bias and repeatability
range are within the permissible limits given in Table E.1, the machine may be regarded as satisfactory.
If not, verify that the indenter, specimen holder, and tester are in good condition and repeat the test. If
the machine continues to fail the daily test, an indirect verification of the testing machine, according to
ISO 6508-2, shall be performed.
A record of the daily verification results should be maintained over a period of time, and used to
measure reproducibility and monitor drift of the machine.
E.2 Bias
The bias, b, of the testing machine in Rockwell units, under the particular verification conditions, is
expressed by Formula (E.1):
bH=−H (E.1)
CRM
where
is the mean hardness value from Formula (E.2);
H
H
is the certified hardness of the reference block used.
CRM
The mean hardness value of the indentations H is defined according to Formula (E.2):
HH++.
1 n
H= (E.2)
n
where
H , H , H , H , …, H are the hardness values corresponding to all the indentations arranged in
1 2 3 4 n
increasing order of magnitude;
n is the total number of indentations.
E.3 Repeatability range
To determine the repeatability range for each reference block, let H ,…,H be the values of the measured
1 n
hardness arranged in increasing order of magnitude.
ISO 6508-1:2023(E)
The repeatability range, r, of the testing machine in Rockwell units, under the particular verification
conditions, is determined by Formula (E.3):
rH=−H (E.3)
n 1
Table E.1 — Permissible repeatability range and bias of the testing machine
Rockwell hardness Hardness range of Permissible bias, b Maximum permissible repeat-
scale the reference block ability range, r, of the testing
machine
A 20 to ≤75 HRA ±2 HRA
0,02 (100 - H ) or
>75 to ≤95 HRA ±1,5 HRA
a
0,8 HRA
10 to ≤45 HRBW ±4 HRBW
0,04 (130 - H )
B >45 to ≤80 HRBW ±3 HRBW
>80 to ≤100 HRBW ±2 HRBW
C 10 to ≤70 HRC ±1,5 HRC
0,02 (100 - H ) or
a
0,8 HRC
D 40 to ≤70 HRD ±2 HRD
0,02 (100 - H ) or
>70 to ≤77 HRD ±1,5 HRD
a
0,8 HRD
E 70 to ≤90 HREW ±2,5 HREW
0,04 (130 - H )
>90 to ≤100 HREW ±2 HREW
F 60 to ≤90 HRFW ±3 HRFW
0,04 (130 - H )
>90 to ≤100 HRFW ±2 HRFW
G 30 to ≤50 HRGW ±6 HRGW
0,04 (130 - H )
>50 to ≤75 HRGW ±4,5 HRGW
>75 to ≤94 HRGW ±3 HRGW
H 80 to ≤100 HRHW ±2 HRHW
0,04 (130 - H )
K 40 to ≤60 HRKW ±4 HRKW
0,04 (130 - H )
>60 to ≤80 HRKW ±3 HRKW
>80 to ≤100 HRKW ±2 HRKW
15N, 30N, 45N All ranges ±2 HRN
0,04 (100 - H ) or
a
1,2 HRN
15T, 30T, 45T All ranges ±3 HRTW
0,06 (100 - H ) or
a
2,4 HRTW
a
Whichever is greater.
EXAMPLE 1
A low-hardness HRC block gave the following daily verification results:
24,0 HRC and 25,2 HRC
From Formula (E.2), it follows that H = 24,6 HRC and from Formula (E.3), it follows that r = 1,2 HRC.
From Table E.1, for the HRC scale, the maximum permissible repeatability range at 24,6 HRC is calculated
0,02 (100 − 24,6) = 1,51 HRC. This is greater than 0,8 HRC; therefore, the maximum permissible
repeatability range of the testing machine for this reference block is 1,51 HRC.
Since r = 1,2 HRC, the repeatability range of the testing machine is acceptable.
EXAMPLE 2
A high-hardness HRC block gave the following daily verification results:
ISO 6508-1:2023(E)
63,1 HRC and 63,9 HRC
From Formula (E.2), it follows that H = 63,5 HRC and from Formula (E.3), it follows that r = 0,8 HRC.
From Table E.1, for the HRC scale, the maximum permissible repeatability range at 63,5 HRC is calculated
0,02 (100 – 63,5) = 0,73 HRC. This is less than 0,8 HRC; therefore, the permissible repeatability range of
the testing machine for this reference block is 0,8 HRC.
Since r = 0,8 HRC, the repeatability range of the testing machine is acceptable.
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