Metallic materials - Rockwell hardness test - Part 2: Verification and calibration of testing machines and indenters (ISO 6508-2:2015)

ISO 6508-2:2015 specifies two separate methods of verification of testing machines (direct and indirect) for determining Rockwell hardness in accordance with ISO 6508‑1:2015, together with a method for verifying Rockwell hardness indenters.
The direct verification method is used to determine whether the main parameters associated with the machine function, such as applied force, depth measurement, and testing cycle timing, fall within specified tolerances. The indirect verification method uses a number of calibrated reference hardness blocks to determine how well the machine can measure a material of known hardness.
The indirect method may be used on its own for periodic routine checking of the machine in service.
If a testing machine is also to be used for other methods of hardness testing, it shall be verified independently for each method.
ISO 6508-2:2015 is applicable to stationary and portable hardness testing machines.
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 may continue to be used only when complying with ISO 6508‑1:2015, Annex A.

Metallische Werkstoffe - Härteprüfung nach Rockwell - Teil 2: Überprüfung und Kalibrierung der Prüfmaschinen und Eindringkörper (ISO 6508-2:2015)

In diesem Teil von ISO 6508 sind zwei unterschiedliche Verfahren für die Überprüfung von Härteprüfmaschinen (direkt und indirekt) zur Bestimmung der Rockwellhärte nach ISO 6508 1 in Verbindung mit einem Verfahren für die Überprüfung von Rockwell-Härteeindringkörpern festgelegt.
Die direkte Überprüfung wird angewendet, um festzustellen, ob die Hauptparameter der Maschinenfunktion, wie z. B. die aufgebrachte Kraft, Eindringtiefenmessung und zeitliche Steuerung der Prüfzyklen, die festgelegten Grenzabweichungen einhalten. Bei der indirekten Überprüfung wird eine Reihe von kalibrierten Härtevergleichsplatten verwendet, um festzustellen, wie gut die Prüfmaschine in der Lage ist einen Werkstoff bekannter Härte zu messen..
Das indirekte Verfahren kann für sich allein zur regelmäßigen Routineüberprüfung der Maschine beim Anwender angewendet werden.
Soll eine Härteprüfmaschine auch für andere Härteprüfverfahren verwendet werden, so muss sie unabhängig für jedes dieser Verfahren überprüft werden.
Dieser Teil von ISO 6508 ist auf ortsfeste und tragbare Härteprüfmaschinen anwendbar.
Es ist zu beachten, dass als Normeindringkugel für die Rockwell-Prüfung nur solche aus Wolframcarbid-Hart-metall gelten. Stahleindringkugeln dürfen nur dann noch verwendet werden, wenn sie ISO 6508 1: , Anhang A entsprechen.

Matériaux métalliques - Essai de dureté Rockwell - Partie 2: Vérification et étalonnage des machines d'essai et des pénétrateurs (ISO 6508-2:2015)

L'ISO 6508-2:2015 spécifie deux méthodes séparées de vérification des machines d'essai (directe et indirecte) pour la détermination de la dureté Rockwell conformément à l'ISO 6508‑1:2015, de même qu'une méthode de vérification des pénétrateurs de dureté Rockwell.
La méthode de vérification directe est utilisée pour déterminer si les principaux paramètres associés aux fonctions de la machine, telles que la force appliquée, le mesurage de l'enfoncement et le phasage du cycle d'essai, se situent dans les tolérances spécifiées. La méthode de vérification indirecte utilise un certain nombre de blocs de dureté de référence étalonnés pour déterminer avec quelle exactitude la machine peut mesurer un matériau de dureté connue.
La méthode indirecte peut être utilisée seule pour une vérification périodique de routine de la machine en service.
Si une machine d'essai est également à utiliser pour d'autres méthodes d'essai de dureté, elle doit être vérifiée indépendamment pour chaque méthode.
L'ISO 6508-2:2015 est applicable aux machines d'essai de dureté fixes et portables.
L'attention est attirée sur le fait que l'utilisation d'un composite en carbure de tungstène pour les pénétrateurs à bille est considérée être le type courant de bille de pénétrateur Rockwell. Des billes de pénétrateur en acier peuvent continuer d'être utilisées seulement lorsqu'elles sont conformes à l'Annexe A de l'ISO 6508‑1:2015.

Kovinski materiali - Preskus trdote po Rockwellu - 2. del: Preverjanje in umerjanje naprav za preskušanje (ISO 6508-2:2015)

Ta del standarda ISO 6508 določa dve metodi preverjanja naprav za preskušanje (neposredno in posredno) za določanje trdote po Rockwellu v skladu s standardom ISO 6508-1:2015, skupaj z metodo za preverjanje vtisnih teles za preskušanje trdote po Rockwellu.
Z neposredno metodo preverjanja se ugotavlja, ali so glavni parametri, povezani z delovanjem naprave, kot so uporabljena sila, meritev globine in čas preskusnega ciklusa, znotraj določenih toleranc. Pri posredni metodi preverjanja se uporabi določeno število umerjenih ploščic referenčne trdote, s katerimi se preveri, kako natančno lahko naprava izmeri material z znano trdoto.
Posredni način se lahko uporabi samostojno pri rednem preverjanju naprave med delovanjem. Če se naprava za preskušanje uporablja tudi za druge metode preskusa trdote, jo je treba preveriti posebej za vsako metodo.
Ta del standarda ISO 6508 se uporablja za nepremične in premične naprave za preskušanje trdote. Opozoriti je treba, da se za standardno vrsto vtisne krogle po Rockwellu šteje kroglično vtisno telo iz kompozita volframovega karbida. Jeklene vtisne krogle se lahko še naprej uporabljajo pod pogojem, da so skladne z dodatkom A k standardu ISO 6508-1:2015.

General Information

Status
Withdrawn
Publication Date
29-Jun-2015
Withdrawal Date
29-Sep-2015
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Start Date
04-Mar-2015
Completion Date
04-Mar-2015

Relations

Buy Standard

Standard
EN ISO 6508-2:2015
English language
31 pages
sale 10% off
Preview
sale 10% off
Preview
e-Library read for
1 day

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 6508-2:2015
01-maj-2015
1DGRPHãþD
SIST EN ISO 6508-2:2006

Kovinski materiali - Preskus trdote po Rockwellu - 2. del: Preverjanje in umerjanje

naprav za preskušanje (ISO 6508-2:2015)

Metallic materials - Rockwell hardness test - Part 2: Verification and calibration of testing

machines and indenters (ISO 6508-2:2015)

Metallische Werkstoffe - Härteprüfung nach Rockwell - Teil 2: Prüfung und Kalibrierung

der Prüfmaschinen und Eindringkörper (ISO 6508-2:2015)

Matériaux métalliques - Essai de dureté Rockwell - Partie 2: Vérification et étalonnage

des machines d'essai (ISO 6508-2:2015)
Ta slovenski standard je istoveten z: EN ISO 6508-2:2015
ICS:
77.040.10 Mehansko preskušanje kovin Mechanical testing of metals
SIST EN ISO 6508-2:2015 en

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

---------------------- Page: 1 ----------------------
SIST EN ISO 6508-2:2015
---------------------- Page: 2 ----------------------
SIST EN ISO 6508-2:2015
EUROPEAN STANDARD
EN ISO 6508-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
March 2015
ICS 77.040.10 Supersedes EN ISO 6508-2:2005
English Version
Metallic materials - Rockwell hardness test - Part 2: Verification
and calibration of testing machines and indenters (ISO 6508-
2:2015)

Matériaux métalliques - Essai de dureté Rockwell - Partie 2: Metallische Werkstoffe - Härteprüfung nach Rockwell - Teil

Vérification et étalonnage des machines d'essai et des 2: Überprüfung und Kalibrierung der Prüfmaschinen und

pénétrateurs (ISO 6508-2:2015) Eindringkörper (ISO 6508-2:2015)
This European Standard was approved by CEN on 10 January 2015.

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

© 2015 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 6508-2:2015 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN ISO 6508-2:2015
EN ISO 6508-2:2015 (E)
Contents
Page

Foreword ..............................................................................................................................................................3

---------------------- Page: 4 ----------------------
SIST EN ISO 6508-2:2015
EN ISO 6508-2:2015 (E)
Foreword

This document (EN ISO 6508-2:2015) 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 September 2015, and conflicting national standards shall be

withdrawn at the latest by September 2015.

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 6508-2:2005.

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 6508-2:2015 has been approved by CEN as EN ISO 6508-2:2015 without any modification.

---------------------- Page: 5 ----------------------
SIST EN ISO 6508-2:2015
---------------------- Page: 6 ----------------------
SIST EN ISO 6508-2:2015
INTERNATIONAL ISO
STANDARD 6508-2
Third edition
2015-03-01
Metallic materials — Rockwell
hardness test —
Part 2:
Verification and calibration of testing
machines and indenters
Matériaux métalliques — Essai de dureté Rockwell —
Partie 2: Vérification et étalonnage des machines d’essai et des
pénétrateurs
Reference number
ISO 6508-2:2015(E)
ISO 2015
---------------------- Page: 7 ----------------------
SIST EN ISO 6508-2:2015
ISO 6508-2:2015(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2015

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
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2015 – All rights reserved
---------------------- Page: 8 ----------------------
SIST EN ISO 6508-2:2015
ISO 6508-2:2015(E)
Contents Page

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

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

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

3 General conditions ............................................................................................................................................................................................. 1

4 Direct verification of the testing machine .................................................................................................................................. 2

4.1 General ........................................................................................................................................................................................................... 2

4.2 Calibration and verification of the test force................................................................................................................. 2

4.3 Calibration and verification of the depth-measuring system ......................................................................... 2

4.4 Calibration and verification of the testing cycle ......................................................................................................... 3

4.5 Calibration and verification of the machine hysteresis........................................................................................ 3

5 Indirect verification of the testing machine ............................................................................................................................. 4

5.1 General ........................................................................................................................................................................................................... 4

5.2 Procedure .................................................................................................................................................................................................... 4

5.3 Repeatability ............................................................................................................................................................................................. 5

5.4 Bias .................................................................................................................................................................................................................... 6

5.5 Uncertainty of measurement ...................................................................................................................................................... 7

6 Calibration and verification of Rockwell hardness indenters ............................................................................... 7

6.1 General ........................................................................................................................................................................................................... 7

6.2 Diamond indenter ................................................................................................................................................................................ 7

6.2.1 General...................................................................................................................................................................................... 7

6.2.2 Direct calibration and verification of the diamond indenter ..................................................... 7

6.2.3 Indirect verification of diamond indenters ............................................................................................... 8

6.3 Ball indenter .............................................................................................................................................................................................. 9

6.3.1 Direct calibration and verification of the ball indenter .................................................................. 9

6.3.2 Indirect verification of the ball holder assembly ..............................................................................11

6.4 Marking ......................................................................................................................................................................................................11

7 Intervals between direct and indirect calibrations and verifications .......................................................11

8 Verification report ...........................................................................................................................................................................................12

Annex A (normative) Repeatability of testing machines ..............................................................................................................13

Annex B (informative) Uncertainty of measurement of the calibration results of the

hardness testing machine ........................................................................................................................................................................15

Bibliography .............................................................................................................................................................................................................................24

© ISO 2015 – All rights reserved iii
---------------------- Page: 9 ----------------------
SIST EN ISO 6508-2:2015
ISO 6508-2:2015(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 WTO principles in the Technical Barriers

to Trade (TBT) see the following URL: Foreword - Supplementary information

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

Subcommittee SC 3, Hardness testing.

This third edition cancels and replaces the first edition (ISO 6508-2:2005), which has been technically

revised.

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 2015 – All rights reserved
---------------------- Page: 10 ----------------------
SIST EN ISO 6508-2:2015
INTERNATIONAL STANDARD ISO 6508-2:2015(E)
Metallic materials — Rockwell hardness test —
Part 2:
Verification and calibration of testing machines and
indenters
1 Scope

This part of ISO 6508 specifies two separate methods of verification of testing machines (direct and

indirect) for determining Rockwell hardness in accordance with ISO 6508-1:2015, together with a

method for verifying Rockwell hardness indenters.

The direct verification method is used to determine whether the main parameters associated with

the machine function, such as applied force, depth measurement, and testing cycle timing, fall within

specified tolerances. The indirect verification method uses a number of calibrated reference hardness

blocks to determine how well the machine can measure a material of known hardness.

The indirect method may be used on its own for periodic routine checking of the machine in service.

If a testing machine is also to be used for other methods of hardness testing, it shall be verified

independently for each method.

This part of ISO 6508 is applicable to stationary and portable hardness testing machines.

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 may continue to be used only

when complying with ISO 6508-1:2015, 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 376, Metallic materials — Calibration of force-proving instruments used for the verification of uniaxial

testing machines
ISO 6507-1, Metallic materials — Vickers hardness test — Part 1: Test method

ISO 6508-1:2015, Metallic materials — Rockwell hardness test — Part 1: Test method

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

3 General conditions

Before a Rockwell hardness testing machine is verified, the machine shall be checked to ensure that it is

properly set up and operating in accordance with the manufacturer’s instructions.

Especially, it should be checked that the test force can be applied and removed without shock, vibration,

or overload and in such a manner that the readings are not influenced.
© ISO 2015 – All rights reserved 1
---------------------- Page: 11 ----------------------
SIST EN ISO 6508-2:2015
ISO 6508-2:2015(E)
4 Direct verification of the testing machine
4.1 General

4.1.1 Direct verification involves calibration and verification of the following:

a) test forces;
b) depth-measuring system;
c) testing cycle;
d) machine hysteresis test.

4.1.2 Direct verification should be carried out at a temperature of (23 ± 5) °C. If the verification is made

outside of this temperature range, this shall be reported in the verification report.

4.1.3 The instruments used for calibration shall be traceable to national standards.

4.1.4 An indirect verification according to Clause 5 shall be performed following a successful direct

verification.
4.2 Calibration and verification of the test force

4.2.1 Each preliminary test force, F , (see 4.2.4) and each total test force, F, used (see 4.2.5) shall be

measured, and, whenever applicable, this shall be done at not less than three positions of the plunger

spaced throughout its range of movement during testing. The preliminary test force shall be held for at

least 2 s.

4.2.2 Three readings shall be taken for each force at each position of the plunger. Immediately before

each reading is taken, the plunger shall be moved in the same direction as during testing.

4.2.3 The forces shall be measured by one of the following two methods:

— by means of a force-proving device according to ISO 376 class 1 or better and calibrated for

reversibility;

— by balancing against a force, accurate to ±0,2 %, applied by means of calibrated masses or by another

method having the same accuracy.

Evidence should be available to demonstrate that the output of the force-proving device does not vary

by more than 0,2 % in the period 1 s to 30 s following a stepped change in force.

4.2.4 The tolerance on each measurement of the preliminary test force, F , (before application and

after removal of the additional test force, F ) shall be ±2,0 %, see Formula (B.2) The range of all force

measurements (highest value minus lowest value) shall be ≤ 1,5 % of F .

4.2.5 The tolerance on each measurement of the total test force, F, shall be ±1,0 %. The range of the

force measurements (highest value minus lowest value) shall be ≤ 0,75 % of F.
4.3 Calibration and verification of the depth-measuring system

4.3.1 The depth-measuring system shall be calibrated by making known incremental movements of the

indenter or the indenter holder.
2 © ISO 2015 – All rights reserved
---------------------- Page: 12 ----------------------
SIST EN ISO 6508-2:2015
ISO 6508-2:2015(E)

4.3.2 The instrument or gauge blocks used to verify the depth-measuring system shall have a maximum

expanded uncertainty of 0,000 3 mm when calculated with a 95 % confidence level.

4.3.3 Calibrate the testing machine’s depth measurement system at not less than four evenly spaced

increments covering the full range of the normal working depth measured by the testing machine. For this

purpose, the working depth is 0,25 mm for regular Rockwell scales (A, C, D, B, E, F, G, H, K), and 0,1 mm for

superficial Rockwell scales (N, T).

4.3.4 Some testing machines have a long-stroke depth measuring system where the location of the

working range of the depth measuring system varies to suit the sample. This type of testing machine shall

be able to electronically verify that the depth measuring device is continuous over the full range. These

types of testers shall be verified using the following steps:

a) At the approximate top, midpoint, and bottom of the total stroke of the measuring device, verify

the depth measurement system at no less than four evenly spaced increments of approximately

0,05 mm at each of the three locations.

b) Operate the actuator over its full range of travel to monitor whether the displacement measurement

is continuous. The displacement indication shall be continuously indicated over the full range.

4.3.5 The depth-measuring system shall correctly indicate within ±0,001 mm for the scales A to K and

within ±0,000 5 mm for scales N and T, i.e. within ±0,5 of a scale unit, over each range.

4.4 Calibration and verification of the testing cycle

4.4.1 The testing cycle is to be calibrated by the testing machine manufacturer at the time of manufacture

and when the testing machine undergoes repair which may have affected the testing cycle. Calibration of

the complete testing cycle is not required as part of the direct verification at other times, see Table 10.

4.4.2 The testing cycle shall conform to the testing cycle defined in ISO 6508-1:2015.

4.4.3 For testing machines that automatically control the testing cycle, the measurement uncertainty

(k = 2) of the timing instrument used to verify the testing cycle shall not exceed 0,2 s. It is recommended

that the measured times for the testing cycle, plus or minus the measurement uncertainty (k = 2) of the

calibration measurements, not exceed the timing limits specified in ISO 6508-1:2015.

4.4.4 For testing machines that require the user to manually control the testing cycle, the testing

machine shall be verified to be capable of achieving the defined testing cycle.
4.5 Calibration and verification of the machine hysteresis

4.5.1 The machine shall be checked to ensure that the readings are not affected by a hysteresial flexure

of testing machine components (e.g. frame, specimen holder, etc.) during a test. The influence of any

hysteresis behaviour shall be checked by making repeated hardness tests using a spherical indenter of

at least 10 mm diameter, bearing directly against the specimen holder or through a spacer such that no

permanent deformation occurs. A parallel block placed between the indenter holder and the specimen

holder may be used instead of a blunt indenter. The material of the blunt indenter and of the spacer or

parallel block shall have a hardness of at least 60 HRC.

4.5.2 Perform repeated Rockwell tests using the setup defined in 4.5.1. The tests shall be conducted

using the Rockwell scale with the highest test force that is used during normal testing. Repeat the

hysteresis verification procedure for a maximum of 10 measurements and average the last three tests.

© ISO 2015 – All rights reserved 3
---------------------- Page: 13 ----------------------
SIST EN ISO 6508-2:2015
ISO 6508-2:2015(E)

4.5.3 The average of the last three tests shall indicate a hardness number of (130 ± 1,0) Rockwell units

when the regular Rockwell ball scales B, E, F, G, H, and K are used, or within (100 ± 1,0) Rockwell units

when any other Rockwell scale is used.
5 Indirect verification of the testing machine
5.1 General

5.1.1 Indirect verification involves the calibration and verification of the testing machine by performing

tests on reference blocks.

5.1.2 Indirect verification should be carried out at a temperature of (23 ± 5) °C by means of reference

blocks calibrated in accordance with ISO 6508-3:2015. If the verification is made outside of this

temperature range, this shall be reported in the verification report.
5.2 Procedure

5.2.1 For the indirect verification of a testing machine, the following procedures shall be applied.

The testing machine shall be verified for each scale for which it will be used. For each scale to be verified,

reference blocks from each of the hardness ranges given in Table 1 shall be used. The hardness values of

the blocks shall be chosen to approximate the limits of the intended use. It is recommended to perform

the same test cycle used when the reference blocks were calibrated.
Only the calibrated surfaces of the test blocks are to be used for testing.

5.2.2 On each reference block, a minimum of five indentations, made in accordance with ISO 6508-

1:2015, shall be uniformly distributed over the test surface and each hardness number observed to within

0,2 HR of a scale unit. Before making these indentations, at least two preliminary indentations shall be

made to ensure that the machine is working freely and that the reference block, the indenter, and the

specimen holder are seating correctly. The results of these preliminary indentations shall be ignored.

Table 1 — Hardness ranges for different scales

Rockwell hardness Hardness range of reference Rockwell hardness Hardness range of reference

scale block scale block
A 20 to 40 HRA K 40 to 60 HRKW
45 to 75 HRA 65 to 80 HRKW
80 to 95 HRA 85 to 100 HRKW
B 10 to 50 HRBW 15N 70 to 77 HR15N
60 to 80 HRBW 78 to 88 HR15N
85 to 100 HRBW 89 to 94 HR15N
C 10 to 30 HRC 30N 42 to 54 HR30N
35 to 55 HRC 55 to 73 HR30N
60 to 70 HRC 74 to 86 HR30N
D 40 to 47 HRD 45N 20 to 31 HR45N
55 to 63 HRD 32 to 61 HR45N
70 to 77 HRD 63 to 77 HR45N
4 © ISO 2015 – All rights reserved
---------------------- Page: 14 ----------------------
SIST EN ISO 6508-2:2015
ISO 6508-2:2015(E)

Rockwell hardness Hardness range of reference Rockwell hardness Hardness range of reference

scale block scale block
E 70 to 77 HREW 15T 67 to 80 HR15TW
84 to 90 HREW 81 to 87 HR15TW
93 to 100 HREW 88 to 93 HR15TW
F 60 to 75 HRFW 30T 29 to 56 HR30TW
80 to 90 HRFW 57 to 69 HR30TW
94 to 100 HRFW 70 to 82 HR30TW
G 30 to 50 HRGW 45T 10 to 33 HR45TW
55 to 75 HRGW 34 to 54 HR45TW
80 to 94 HRGW 55 to 72 HR45TW
H 80 to 94 HRHW
96 to 100 HRHW
5.3 Repeatability

5.3.1 For each reference block, let H , H , H , H ,…..H be the values of the measured hardness arranged

1 2 3 4 n
in increasing order of magnitude.

The repeatability range, r, of the testing machine in Rockwell units, under the particular verification

conditions, is determined by Formula (1):
rH=−H (1)
n 1

The mean hardness value of all indentations H is defined according to Formula (2):

HH++HH++...+H
12 34 n
H= (2)
where
H , H , H , H , H are the hardness values corresponding to all the indentations;
1 2 3 4 ….. n
n is the total number of indentations.

5.3.2 The repeatability range of the testing machine being verified shall be considered satisfactory if it

satisfies the conditions given in Table 2. Permissible repeatability is presented graphically in Figures A.1

and A.2.
Table 2 — Permissible repeatability range and bias of the testing machine
Permissible bias Permissible repeatability
Rockwell hardness Hardness range of
Rockwell units range of the testing machine
scale the reference block
b r
A 20 to 75 HRA ±2 HRA
≤ 0,02 (100 − H ) or
> 75 to 95 HRA ±1,5 HRA
0,8 HRA Rockwell units
H is the mean hardness value.

The one with a greater value becomes the permissible repeatability range of the testing machine.

NOTE The requirements for permissible repeatability range, r, and/or permissible bias, b, might be different in ASTM E 18.

© ISO 2015 – All rights reserved 5
---------------------- Page: 15 ----------------------
SIST EN ISO 6508-2:2015
ISO 6508-2:2015(E)
Permissible bias Permissible repeatability
Rockwell hardness Hardness range of a
Rockwell units range of the testing machine
scale the reference block
b r
B 10 to 45 HRBW ±4 HRBW
≤ 0,04 (130 − H )
> 45 to 80 HRBW ±3 HRBW
HRBW Rockwell units
> 80 to 100 HRBW ±2 HRBW
C 10 to 70 HRC ±1,5 HRC
≤ 0,02 (100 − H ) or
0,8 HRC Rockwell units
D 40 to 70 HRD ±2 HRD
≤ 0,02 (100 − H ) or
> 70 to 77 HRD ±1,5 HRD
0,8 HRD Rockwell units
E 70 to 90 HREW ±2,5 HREW
≤ 0,04 (130 − H )
> 90 to 100 HREW ±2 HREW
HREW Rockwell units
F 60 to 90 HRFW ±3 HRFW
≤ 0,04 (130 − H )
> 90 to 100 HRFW ±2 HRFW
HRFW Rockwell units
G 30 to 50 HRGW ±6 HRGW
≤ 0,04 (130 − H )
> 50 to 75 HRGW ±4,5 HRGW
HRGW Rockwell units
> 75 to 94 HRGW ±3 HRGW
H 80 to 100 HRHW ±2 HRHW
≤ 0,04 (130 − H )
HRHW Rockwell units
K 40 to 60 HRKW ±4 HRKW
≤ 0,04 (130 − H )
> 60 to 80 HRKW ±3 HRKW
HRKW Rockwell units
> 80 to 100 HRKW ±2 HRKW
15N, 30N, 45N All ranges ±2 HR-N
≤ 0,04 (100 − H ) or
1,2 HR-N Rockwell units
15T, 30T, 45T All ranges ±3 HR-TW
≤ 0,06 (100 − H ) or
2,4 HR-TW Rockwell units
H is the mean hardness value.

The one with a greater value becomes the permissible repeatability range of the testing machine.

NOTE The requirements for permissible repeatability range, r, and/or permissible bias, b, might be different in ASTM E 18.

5.4 Bias

5.4.1 The bias, b, of the testing machine in Rockwell units, under the particular calibration conditions,

is expressed by the following formula:
bH=−H (3)
CRM
where
6 © ISO 2015 – All rights reserved
---------------------- Page: 16 ----------------------
SIST EN ISO 6508-2:2015
ISO 6508-2:2015(E)
is the mean hardness value, from Formula (2);
H is the certified hardness of the reference block used.
CRM
5.4.2 The bias of the testing machine shall not exceed the values g
...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.