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IS0
I N T ERN AT1 O NA L O RG A N I Z AT1 O N FO R STA N DARD IZATlO N
IS0 RECOMMENDATION
i
R 640
CALIBRATION OF STANDARDIZED BLOCKS TO BE USED
FOR VICKERS HARDNESS TESTING MACHINES
1st EDITION
November 1967
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of IS0 Recommendations and IS0 Standards
The copyright
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations
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BRIEF HISTORY
The IS0 Recommendation R 640, Calibration of Standardized Blocks to be Used for Vickers
Hardness Testing Machines, was drawn up by Technical Committee ISO/TC 17, Steel, the Secre-
tariat of which is held by the British Standards Institution (BSI).
Work on this question by the Technical Committee began in 1961 and led, in 1965, to the
adoption of a Draft IS0 Recommendation.
L
In February 1966, this Draft IS0 Recommendation (No. 923) which superseded Draft IS0
Recommendation No. 524, was circulated to all the IS0 Member Bodies for enquiry. It was
approved, subject to a few modifications of an editorial nature, by the following Member Bodies:
Hungary Republic of South Africa
Argentina
Australia India Romania
Austria Israel Spain
Belgium Italy Sweden
Turkey
Canada Japan
Chile Korea, Rep. of U.A.R.
Czechoslovakia Mexico United Kingdom
Denmark Net herlands U.S.A.
U.S.S.R.
Finland New Zealand
France Norway Yugoslavia
Germany Poland
No Member Body opposed the approval of the Draft.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0
Council, which decided, in November 1967, to accept it as an IS0 RECOMMENDATION.
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ISO/R 640 - 1961 (E)
IS0 Recommendation R 640 November 1967
CALIBRATION OF STANDARDIZED BLOCKS TO BE USED
FOR VICKERS HARDNESS TESTING MACHINES
1. SCOPE
This IS0 Recommendation applies to the calibration of standardized blocks for the indirect
verification of hardness testing machines as described in IS0 Recommendation R 146,* VeriJica-
tion of Vickers Hardness Testing Machines. It does not necessarily apply to the calibration of test
blocks which are used in the routine checking of the testing machine by the user, but it is not
intended to preclude the use of blocks calibrated in accordance with this IS0 Recommendation
for the routine checking of a machine.**
2. MANUFACTURE
2.1 Each metal block to be standardized should be of a thickness not less than 6 mm (1/4 in).
2.2 The block should be especially prepared and the attention of the manufacturer is drawn to
the need to use a manufacturing process which will give the necessary homogeneity, stability
of structure and uniformity of surface hardness. It is recommended that the fineness and
regularity of grain and the uniformity of the metallurgical structure be verified by micro-
scopical examination. A microscopical examination may also be made by the standardizing
authority.
2.3 It is recommended that the manu-
The standardized blocks should not be magnetized.
facturer should ensure that the blocks, if of steel, have been demagnetized.
2.4 The upper and lower surfaces of the standardized block should be flat within 0.005 mm and
the parallelism of the block should be such that the thickness does not vary by more than
0.010 mm per 50 mm.
2.5 The lower surface of the standardized block should have a fine ground finish.
2.6 The test surface (upper surface) should be highly polished and its surface roughness should
not exceed 0.0001 mm (centre line average). It should also be free from scratches which
interfere with the measurement of the indentations.
2.7 To permit checking that no material is subsequently removed from the standardized block,
its thickness at the time of standardization should be marked on it to the nearest 0.01 mm
(0.0004 in), or an official mark should be made on the test surface (see section 13).
* 2nd edition, at present Draft IS0 Recommendation No. 922.
** Test blocks that are used in routine checking of the testing machine may be calibrated, using the load duration specified
in clause 4.2 of IS0 Recommendation R 81 (2nd edition - 1967), Vickers Hardness Test for Sreel (Load5 to 100 kgf).
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ISO/R 640 - 1967 (E)
3. STANDARDIZING PROCEDURE
The standardized blocks should be calibrated in a standardizing machine complying with the
requirements of sections 4 to 8 at a temperature of 20 f 2 "C in temperate climates and 27 f 2 "C
in tropical climates using the general procedure described in IS0 Recommendation R 8 1,
(2nd edition - 1967) Vickers Hardness Test for Steel (Load 5 to 100 kgf).
4. STANDARDIZING MACHINE
The standardizing machine is one in which the load applied, the form of the indenter and the
measuring device can be verified by fundamental measurement. The load should be applied by
means of weights giving correct values of force.
5. LOADS
The loads should be correct within & 0.1 %.
6. FORM OF INDENTER
6.1
The four faces of the diamond pyramid at the tip of the indenter should be highly polished,
free from flaws, and flat within 0.0002 mm.
The angle between opposite faces of the diamond pyramid should be 136 f 0.1".
The angle between the four faces of the pyramid and the axis of the indenter should be
68 it 0.3".
6.2 The p
...