|
Ref. No. : ISO/R 716-1968 (E)
IS0
ORGAN I2 AT I ON FOR STAN DARD IZATl O N
I N T E RN AT1 O N A L
I SO R ECO M M EN DATI O N
R 716
VERIFICATION OF ROCKWELL B AND C SCALE
HARDNESS TESTING MACHINES
1 st EDITION
May 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.
---------------------- Page: 1 ----------------------
BRIEF HISTORY
The IS0 Recommendation R 716, Verification of Rockwell B and C scale hardness testing
machines, was drawn up by Technical Committee ISO/TC 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 replaced Draft IS0 Recommendation No. 522.
W-
In March 1966, this Draft IS0 Recommendation (No. 928) 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 :
Argentina Israel Sweden
Austria Italy Switzerland
Belgium
Japan Turkey
Canada Korea, Rep. of
U.A.R.
Chile Netherlands United Kingdom
Czechoslovakia New Zealand U.S.A.
Denmark Norway U.S.S.R.
Finland Portugal Yugoslavia
France Romania
Germany South Africa,
Rep. of
Hu%asr
India
Spain
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 May 1968, to accept it as an IS0 RECOMMENDATION.
-2-
---------------------- Page: 2 ----------------------
ISO/R 716-1968 (f
IS0 Recommendation R 716 May 1968
VERIFICATION OF ROCKWELL 6 AND C SCALE
HARDNESS TESTING MACHINES
1. SCOPE
This IS0 Recommendation applies to the verification of testing machines for determining Rockwell
hardness in accordance with IS0 Recommendation R 80,* Rockwell hardness test (B and C scales)
for steel.
It describes the indirect method which is suitable for machines in service, and the direct method which
is suitable for the initial verification of new machines by the manufacturer and for the verification of
rebuilt machines.
2. DIRECT VERIFICATION
Direct verification involves
verification of the load-applying mechanism (see clause 2.1),
(a)
verification of the indenter (see clause 2.2),
(b)
verification of the measuring device (see clause 2.3).
(c)
Before verification is carried out, certain details of the testing machine should be checked (see
Annex A).
2.1 Verification of the load-applying mechanism
2.1.1 The verification of the load-applying mechanism at the required loads should be carried out
either by means of standardized weights (masses) or by means of an elastic device or proving
levers.
2.1.2 The preliminary load and each total load should be measured and, wherever possible, this
should be done at not less than three positions of the plunger throughout its range of move-
ment.
2.1.3 The loads should be measured by one of the following three methods :
balancing against standardized weights (masses) accurate to f 0.1
(a)
balancing against a load, accurate to f 0.2 applied by means of standardized
(b)
weights (masses) with mechanical advantage;
measuring the applied load by means of the deformation of an elastic device'which
(c)
has been previously calibrated to an accuracy off 0.2
2.1.4 Three readings should be taken for each load at each position of the plunger (see clause
2.1.2). Immediately before each reading is taken, the plunger should have been moved in the
same direction as during testing.
* 2nd edition, 1968.
-3-
---------------------- Page: 3 ----------------------
ISO/R 716-1968 (E)
2.1.5 Each reading of the preliminary load before application and after removal of the additional
load should be
10 f 0.2 kgf
Each reading of the total load should be
150 f 0.9 kgf for a cone indenter (C scale),
100 f 0.65 kgf for a bail indenter (B scale),
2.2 Verification of the indenter (B and C scales)
2.2.1 Cscale
The verification of the form of the diamond cone can be made by direct measure-
2.2.1.1
ment or by measurement of its projection on a screen. The verification should be made
at not less than four sections.
2.2.1.2 The diamond cone should have an included angle of 120 f 0.5" and should have its
axis in line with the axis of the indenter within 0.5". The tip of the cone should be
spherical with a radius equal to 0.200 mm. The contour of the whole of the tip should
not depart by more than 0.002 mm from the theoretical profile (see Figure, below).
The surface of the cone should blend in a truly tangential manner with the surface of
the spherical tip.
- - - - Nominal radius 0.2 mm
- - - - - Tolerance boundaries '\
a b Minimum permissible radius
C d Maximum permissible radius
FIGURE
2.2.1.3 The hardness values given by the testing machine do not depend only on the dimensions
given in clause 2.2.1.2, but also on the surface roughness and the position of the
crystallographic axes of the diamond, and the seating of the diamond in its holder.
For this reason, a performance test is considered necessary. The indenter should be used
in a standardizing machine, in which the load applied and the measuring device can be
verified by fundamental measurement.
An indenter should be rejected if, during the performance test, the hardness values
obtained differ by more than 1 Rockwell unit (in the range 30 to 65 HRC) from those
of the standardized blocks calibrated with an accepted indenter.
-4-
---------------------- Page: 4 ----------------------
ISO/R 716-1968 (E
2.2.2 BScale
2.2.2.1 For the purpose of verifying the size and hardness of the steel ball used in the indenter,
it is considered sufficient to test a sample selected at random from a batch. The
ball(s) tested for hardness should be discarded.
2.2.2.2 The balls should satisfy the following requirements :
the diameter, when measured at not less than three positions, should not differ
(a)
from the nominal diameter by more than 0.0035 mm (0.00015 in);*
the Vickers hardness of the balls should not be less than 850 HV 10 when
(b)
measured in accordance with IS0 Recommendation R 81,** Vickers hardness
test for steel, and applying the appropriate correction for curvature as given in
IS0 Recommendation R 409, Table of Vickers hardness values (HV) for metallic
materials. The maximum value of the mean diagonal of the indentation made
with a Vickers indenter at 10 kgf is therefore 0.141 mm for a 1.5875 mm
(1/16 in) ball.
2.3 Verificatio
...