Metallic materials - Rockwell hardness test - Part 1: Test method (ISO 6508-1:2016)

ISO 6508-1:2016 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 (for instance, ISO 3738‑1 and ISO 4498).

Metallische Werkstoffe - Härteprüfung nach Rockwell - Teil 1: Prüfverfahren (ISO 6508-1:2016)

Dieser Teil von ISO 6508 legt das Standard-Rockwell- und Superrockwell-Verfahren für die Skalen A, B, C, D, E, F, G, H, K, 15N, 30N, 45N, 15T, 30T and 45T für metallische Werkstoffe fest und gilt für ortsfeste und ortsbewegliche Härteprüfmaschinen.
Für Sonderwerkstoffe und/oder  erzeugnisse gelten besondere Internationale Normen (z. B. ISO 3738 1 und ISO 4498).
ANMERKUNG   Es ist zu beachten, dass als Normeindringkugeln für die Rockwell-Prüfung nur solche aus Wolframcarbidgemischkugeln gelten. Eindringkugeln aus Stahl dürfen nur dann noch verwendet werden, wenn sie Anhang A entsprechen.

Matériaux métalliques - Essai de dureté Rockwell - Partie 1: Méthode d'essai (ISO 6508-1:2016)

L'ISO 6508-1 :2016 spécifie la méthode d'essai de dureté Rockwell normale et de dureté superficielle Rockwell pour les échelles A, B, C, D, E, F, G, H, K,15N,30N,45N,15T,30T et 45 T pour les matériaux métalliques. Elle s'applique aux machines d'essai de dureté fixes et portables.
Pour des matériaux et/ou produits spécifiques, d'autres Normes internationales spécifiques s'appliquent (par exemple ISO 3738‑1 et ISO 4498).

Kovinski materiali - Preskus trdote po Rockwellu - 1. del: Preskusna metoda (ISO 6508-1:2016)

Ta del standarda ISO 6508 določa metodo običajnega preskusa trdote po Rockwellu in preskusa trdote
z majhnimi obremenitvami po Rockwellu za vrednosti A, B, C, D, E, F, G, H, K,15N, 30N, 45N, 15T, 30T in 45T za kovinske materiale in se uporablja za nepremične in premične naprave za preskušanje trdote.
Za določene materiale in/ali izdelke se uporabljajo drugi ustrezni mednarodni standardi (na primer
standarda ISO 3738-1 in ISO 4498).
OPOMBA: Opozoriti je treba, da se za standardno vrsto vtisne krogle po Rockwellu šteje
kroglično vtisno telo iz kompozita volframovega karbida. Uporaba jeklenih vtisnih krogel je še naprej dovoljena pod pogojem, da so skladne z dodatkom A.

General Information

Status
Withdrawn
Publication Date
29-Nov-2016
Withdrawal Date
27-Feb-2017
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Start Date
31-Aug-2016
Completion Date
31-Aug-2016

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SLOVENSKI STANDARD
SIST EN ISO 6508-1:2016
01-november-2016
1DGRPHãþD
SIST EN ISO 6508-1:2015
Kovinski materiali - Preskus trdote po Rockwellu - 1. del: Preskusna metoda (ISO
6508-1:2016)

Metallic materials - Rockwell hardness test - Part 1: Test method (ISO 6508-1:2016)

Metallische Werkstoffe - Härteprüfung nach Rockwell - Teil 1: Prüfverfahren (ISO 6508-

1:2016)

Matériaux métalliques - Essai de dureté Rockwell - Partie 1: Méthode d'essai (ISO 6508-

1:2016)
Ta slovenski standard je istoveten z: EN ISO 6508-1:2016
ICS:
77.040.10 Mehansko preskušanje kovin Mechanical testing of metals
SIST EN ISO 6508-1:2016 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 6508-1:2016
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SIST EN ISO 6508-1:2016
EN ISO 6508-1
EUROPEAN STANDARD
NORME EUROPÉENNE
August 2016
EUROPÄISCHE NORM
ICS 77.040.10 Supersedes EN ISO 6508-1:2015
English Version
Metallic materials - Rockwell hardness test - Part 1: Test
method (ISO 6508-1:2016)

Matériaux métalliques - Essai de dureté Rockwell - Metallische Werkstoffe - Härteprüfung nach Rockwell -

Partie 1: Méthode d'essai (ISO 6508-1:2016) Teil 1: Prüfverfahren (ISO 6508-1:2016)

This European Standard was approved by CEN on 23 July 2016.

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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 6508-1:2016 E

worldwide for CEN national Members.
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SIST EN ISO 6508-1:2016
EN ISO 6508-1:2016 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 6508-1:2016
EN ISO 6508-1:2016 (E)
European foreword

This document (EN ISO 6508-1:2016) has been prepared by Technical Committee ISO/TC 164

“Mechanical testing of metals” in collaboration with Technical Committee ECISS/TC 101 “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 February 2017, and conflicting national standards

shall be withdrawn at the latest by February 2017.

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 6508-1:2015.

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, Former Yugoslav Republic of Macedonia,

France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,

Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
Endorsement notice

The text of ISO 6508-1:2016 has been approved by CEN as EN ISO 6508-1:2016 without any

modification.
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SIST EN ISO 6508-1:2016
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SIST EN ISO 6508-1:2016
INTERNATIONAL ISO
STANDARD 6508-1
Fourth edition
2016-08-15
Metallic materials — Rockwell
hardness test —
Part 1:
Test method
Matériaux métalliques — Essai de dureté Rockwell —
Partie 1: Méthode d’essai
Reference number
ISO 6508-1:2016(E)
ISO 2016
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SIST EN ISO 6508-1:2016
ISO 6508-1:2016(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2016, Published in Switzerland

All rights reserved. Unless otherwise specified, 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
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2016 – All rights reserved
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SIST EN ISO 6508-1:2016
ISO 6508-1:2016(E)
Contents Page

Foreword .......................................................................................................................................................................................................................................iv

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

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

3 Principle ........................................................................................................................................................................................................................ 1

4 Symbols, abbreviated terms and designations ..................................................................................................................... 2

5 Testing machine .................................................................................................................................................................................................... 4

6 Test piece ...................................................................................................................................................................................................................... 5

7 Procedure..................................................................................................................................................................................................................... 5

8 Uncertainty of the results ............................................................................................................................................................................ 7

9 Test report ................................................................................................................................................................................................................... 7

10 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 .....................................................................................................28

Annex I (informative) Rockwell hardness measurement traceability............................................................................29

Bibliography .............................................................................................................................................................................................................................32

© ISO 2016 – All rights reserved iii
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SIST EN ISO 6508-1:2016
ISO 6508-1:2016(E)
Foreword

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

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

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

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

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

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

electrotechnical standardization.

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

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

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

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

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

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

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

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

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

constitute an endorsement.

For an explanation on 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 the following URL: www.iso.org/iso/foreword.html .

The committee responsible for this document is ISO/TC 164, Mechanical testing of metals, Subcommittee

SC 3, Hardness testing.

This fourth edition cancels and replaces the third edition (ISO 6508-1:2015), of which it constitutes a

minor revision in order to clarify the scope of this part of ISO 6508.

ISO 6508 consists of the following parts, under the general title Metallic materials — Rockwell

hardness test:
— Part 1: Test method
— Part 2: Verification and calibration of testing machines and indenters
— Part 3: Calibration of reference blocks
iv © ISO 2016 – All rights reserved
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SIST EN ISO 6508-1:2016
INTERNATIONAL STANDARD ISO 6508-1:2016(E)
Metallic materials — Rockwell hardness test —
Part 1:
Test method
1 Scope

This part of ISO 6508 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 (for instance,

ISO 3738-1 and ISO 4498).

NOTE Attention is drawn to the fact that the use of tungsten carbide composite for ball indenters is

considered to be the standard type of Rockwell indenter ball. Steel indenter balls are allowed to continue to be

used only when complying with Annex A.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 6508-2:2015, Metallic materials — Rockwell hardness test — Part 2: Verification and calibration of

testing machines and indenters

ISO 6508-3:2015, Metallic materials — Rockwell hardness test — Part 3: Calibration of reference blocks

3 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 defined in Clause 7. 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 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):

Rockwell hardness=−N (1)
© ISO 2016 – All rights reserved 1
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SIST EN ISO 6508-1:2016
ISO 6508-1:2016(E)
4 Symbols, abbreviated terms and designations
4.1 See Table 1, Table 2, Table 3, and Figure 1.
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
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
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

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
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
2 © ISO 2016 – All rights reserved
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SIST EN ISO 6508-1:2016
ISO 6508-1:2016(E)

Scales using indenter balls with diameter 6,350 mm and 12,70 mm may also be used, if specified in

[11]

the product specification or by special agreement. See ASTM E18 for additional scales using these

ball sizes.

NOTE 1 For certain materials, the applicable range of application might be narrower than those indicated.

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
additional test force (permanent indentation depth)
HRA
HRC Rockwell Regular hardness =100−
0,002
HRD
HRBW
HREW
HRFW
Rockwell Regular hardness =130−
0,002
HRGW
HRHW
HRKW
HRN
Rockwell Superficial hardness =100−
0,001
HRTW
4.2 The following is an example of the designation of Rockwell hardness.
EXAMPLE
70 HR 30 T W
indication of type of ball used, W = Tungsten carbide
composite
Rockwell scale symbol (see Tables 1 or 2)
Rockwell hardness symbol
Rockwell hardness value

NOTE 1 Previous versions of this part of ISO 6508 allowed the use of steel indenter balls, which required the

suffix S.

NOTE 2 For the HR30TSm and HR15TSm scales defined in Annex A, a capital S and a lower-case m is used

indicating the use of steel indenter balls and a diamond spot specimen holder.
© ISO 2016 – All rights reserved 3
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SIST EN ISO 6508-1:2016
ISO 6508-1:2016(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 Testing machine

5.1 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 defined in Clause 7, and

complying with all of the requirements defined in ISO 6508-2.

5.2 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
— both the regular and the superficial Rockwell diamond scales.

5.3 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 defined in ISO 6508-2:2015,

6.3.1, and meets the performance requirements of ISO 6508-2:2015, 6.3.2.
4 © ISO 2016 – All rights reserved
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SIST EN ISO 6508-1:2016
ISO 6508-1:2016(E)

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.
6 Test piece

6.1 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.

6.2 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.

6.3 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.

See Annex A for special requirements for testing very thin sheet metal using the HR30TSm and

HR15TSm scales.
6.4 For tests on convex cylindrical surfaces and spherical surfaces, see 7.11.
7 Procedure

7.1 This part of ISO 6508 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.

7.2 The daily verification defined 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.

7.3 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 defined in

Annex E.
© ISO 2016 – All rights reserved 5
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SIST EN ISO 6508-1:2016
ISO 6508-1:2016(E)

7.4 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 defined in ISO 6508-2:2015, Table 1) for each Rockwell scale that is

normally used. This does not apply to replacing a ball.

7.5 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 centering 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 centering V-blocks,

and the specimen holder of the testing machine, since any perpendicular misalignment might result in

incorrect results.

7.6 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,

F , shall be 3 s.
NOTE The requirements for the time durations are given with asymmetric limits.

EXAMPLE 3 s indicates that 3 s is the ideal time duration, with an acceptable range of not less than

1 s (3 s - 2 s) to not more than 4 s (3 s + 1 s).
7.7 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.

7.8 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 might be 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.

7.9 The total test force, F, shall be maintained for a duration of 5 s. Remove the additional test force,

F , and, while the preliminary test force, F , is maintained, after 4 s, the final reading shall be made.

1 0

As an exception for test materials exhibiting excessive plastic flow (indentation creep) during the

application of the total test force, special considerations might 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).
6 © ISO 2016 – All rights reserved
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SIST EN ISO 6508-1:2016
ISO 6508-1:2016(E)

7.10 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.

7.11 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.

7.12 Throughout the test, the apparatus shall be protected from shock or vibration.

7.13 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.
8 Uncertainty of the results
[3]

A complete evaluation of the uncertainty should be done according to ISO/IEC Guide 98-3.

Independent of the type of sources, for hardness, there are two possibilities for the determination of the

uncertainty.

— One possibility is based on the evaluation of all relevant sources appearing during a direct calibration.

[4]
As a reference, an EURAMET Guide CG-16 is available.

— The other possibility is based on indirect calibration using a hardness reference block (abbreviated

[2][3][4][5]

as CRM certified reference material). A guideline for the determination is given in Annex G.

9 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 part of ISO 6508, i.e. ISO 6508-1;

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 defined in 4.2;

e) all operations not specified in this part of ISO 6508, or regarded as optional;

f) details of any occurrence which might have affected the result;

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

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shall be specified (see ISO 18265 ).
© ISO 2016 – All rights reserved 7
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SIST EN ISO 6508-1:2016
ISO 6508-1:2016(E)
10 Conversions to other hardness scales or
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