23
ASTM Hardness
Round Correction Factors
Corrections to be added to test results in the following scales for various diameter parts
Corrections to be added to Rockwell C, A, and D values
Hardness
Diameter of Convex Cylindrical Surfaces
Reading
1/4 inc
3/8 in
1/2 in
5/8 in
3/4 in
7/8 in
1 in
1-1/4 in
1-1/2 in
6.4 mm
10 mm
13 mm
16 mm
19 mm
22 mm
25 mm
32 mm
38 mm
20 6.0 4.5 3.5 2.5 2.0 1.5 1.5 1.0 1.0
25 5.5 4.0 3.0 2.5 2.0 1.5 1.0 1.0 1.0
30 5.0 3.5 2.5 2.0 1.5 1.5 1.0 1.0 0.5
35 4.0 3.0 2.0 1.5 1.5 1.0 1.0 0.5 0.5
40 3.5 2.5 2.0 1.5 1.0 1.0 1.0 0.5 0.5
45 3.0 2.0 1.5 1.0 1.0 1.0 0.5 0.5 0.5
50 2.5 2.0 1.5 1.0 1.0 0.5 0.5 0.5 0.5
55 2.0 1.5 1.0 1.0 0.5 0.5 0.5 0.5 0
60 1.5 1.0 1.0 0.5 0.5 0.5 0.5 0 0
65 1.5 1.0 1.0 0.5 0.5 0.5 0.5 0 0
70 1.0 1.0 0.5 0.5 0.5 0.5 0.5 0 0
75 1.0 0.5 0.5 0.5 0.5 0.5 0 0 0
80
0.5
0.5
0.5
0.5
0.5 0 0 0 0
85
0.5
0.5
0.5 0 0 0 0 0 0
90
0.5 0 0 0 0 0 0 0 0
Hardness
Diameters of Convex Cylindrical
Surfaces
Reading 1/4 in
3/8 in
1/2 in
5/8 in
3/4 in
7/8 in
1 in
6.4 mm
10mm
13mm
16 mm
19 mm
22 mm
25 mm
0 12.5 8.5 6.5 5.5 4.5 3.5 3.0
10 12.0 8.0 6.0 5.0 4.0 3.5 3.0
20 11.0 7.5 5.5 4.5 4.0 3.5 3.0
30 10.0 6.5 5.0 4.5 3.5 3.0 2.5
40 9.0 6.0 4.5 4.0 3.0 2.5 2.5
50 8.0 5.5 4.0 3.5 3.0 2.5 2.0
60 7.0 5.0 3.5 3.0 2.5 2.0 2.0
70 6.0 4.0 3.0 2.5 2.0 2.0 1.5
80 5.0 3.5 2.5 2.0 1.5 1.5 1.5
90 4.0 3.0 2.0 1.5 1.5 1.5 1.0
100 3.5 2.5 1.5 1.5 1.0 1.0 0.5
When testing cylindrical specimens, the accuracy of the test will be seriously affected by alignment of elevating screw, Vee-
anvil, indenters, surface finish, and the straightness of the cylinder. These corrections are approximate only and represent the
averages, to the nearest 0.5. Rockwell and Rockwell superficial numbers, of numerous actual observations.
The above tables are from ASTM E 18
Reprinted from the Annual Book of STM Standards, copyright American Society for Testing and Materials.
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