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Ref. No. : ISO/R674-1968 (E)
IS0
INTERN AT I ON AL ORGAN I Z AT1 O N FOR STAND A RD IZATl O N
IS0 RECOMMENDATION
R 674
CALIBRATION OF STANDARDIZED BLOCKS
TO BE USED FOR ROCKWELL B AND C SCALE
HARDNESS TESTING MACHINES
1st EDITION
February 1968
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
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 674, Calibration of standardized blocks to be used for Rockwell
B und C scale hardness testing machines, was drawn up by Technical Committee ISOlTC 17, Steel,
the Secretariat 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, which cancelled and replaced Draft IS0 Recommen-
dation No. 523.
In March 1966, this Draft IS0 Recommendation (No. 929) 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 :
J
Argentina India South Africa,
Austria Israel Rep. of
Belgium Italy Spain
Canada Japan Sweden
Czechoslovakia Korea, Rep. of
Switzerland
Denmark Netherlands
Turkey
Finland New Zealand
U.A.R.
France Norway
United Kingdom
Germany Poland U.S.S.R.
Romania Yugoslavia
Hungary
One Member Body opposed the approval of the Draft :
U.S.A.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council,
which decided, in February 1968, to accept it as an IS0 RECOMMENDATION.
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ISO/R 674-1968 (E)
IS0 Recommendation. R 674 February 1968
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., * Verification of
Rockwell B and C scale 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.
NOTE. - Test blocks which are used in routine checking of the testing machine may be calibrated using the load
duration specified in clause 4.4 of IS0 Recommendation R 80 (2nd edition), Rockwell hardness fesf (I3 and C scales/
for steel.
2. MANUFACTURE
Each metai block to be standardized should be of a thickness of not less than 6 mm (1/4 in).
2.1
The block should be specially prepared and the attention of the manufacturer is drawn to the
2.2
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 .
The standardized blocks should not be magnetized. It is recommended that the manufacturer
2.3
should ensure that the blocks, if of steel, have been demagnetized.
2.4 The upper and lower surfaces of the standardized block should be fiai 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 polished and its surface roughness should not exceed
0.0003 mm (centre line average).
It should be noted that the surface of the standardized block is necessarily work-hardened by
any machining and polishing process. It is necessary to ensure that the machining and final
polishing processes are such that the work-hardening effects are uniform over the surface and
do not penetrate to too great a depth.
2.1 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 0.1 nim
(0.004 in), or an official mark should be made on the test surface (see section 13).
*
At present Draft IS0 Recommendation No. 928
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ISO/R.674-1%8 (Ë
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 80 (2nd
edition), Rockwell hardness test (B and C scales) for steel.
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 I O. 1 O/".
6
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