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Roundness Correction Chart for Hardness Testing
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 in | 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 | 1.0 | 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 |
| Corrections to be added to Rockwell B, F, and G values | |||||||||
| 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.