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| ==Scales and values== | | ==Scales and values== |
| There are several alternative scales, the most commonly used being the "B" and "C" scales. Both express hardness as an arbitrary [[dimensionless number]]. | | There are several alternative scales, the most commonly used being the "B" and "C" scales. Both express hardness as an arbitrary [[dimensionless number]]. |
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| {| class="wikitable" border="1"
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| |+ Various Rockwell scales
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| |-
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| ! Scale !! Abbreviation !! Load !! Indenter !! Use
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| !N
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| !s
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| |-
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| | A || HRA || 60 [[Kilogram-force|kgf]] || 120° diamond spheroconical<sup>†</sup> || [[Tungsten carbide]]
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| |100
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| |0.002mm
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| |-
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| | B || HRB || 100 kgf || {{convert|1/16|in|mm|adj=mid|-diameter|3}} steel sphere || Aluminium, brass, and soft steels
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| |130
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| |0.002mm
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| |-
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| | C || HRC || 150 kgf || 120° diamond spheroconical || Harder steels >B100
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| |100
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| |0.002mm
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| |-
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| | D || HRD || 100 kgf || 120° diamond spheroconical
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| |100
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| |0.002mm
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| |-
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| | E || HRE || 100 kgf || {{convert|1/8|in|mm|adj=mid|-diameter|3}} steel sphere
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| |130
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| |0.002mm
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| |-
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| | F || HRF || 60 kgf || {{convert|1/16|in|mm|adj=mid|-diameter|3}} steel sphere
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| |130
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| |0.002mm
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| |-
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| | G || HRG || 150 kgf || {{convert|1/16|in|mm|adj=mid|-diameter|3}} steel sphere
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| |130
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| |0.002mm
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| |-
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| | colspan=5 | <sup>†</sup>Also called a ''brale indenter''
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| * Except for testing thin materials in accordance with A623, the steel indenter balls have been replaced by tungsten carbide balls of the varying diameters. When a ball indenter is used, the letter "W" is used to indicate a tungsten carbide ball was used, and the letter "S" indicates the use of a steel ball. E.g.: 70 HRBW indicates the reading was 70 in the Rockwell B scale using a tungsten carbide indenter.<ref>E18-08b Section 5.1.2.1 & 5.2.3</ref>
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| The ''superficial'' Rockwell scales use lower loads and shallower impressions on brittle and very thin materials. The 45N scale employs a 45-kgf load on a diamond cone-shaped Brale indenter, and can be used on dense [[ceramic]]s. The 15T scale employs a 15-kgf load on a {{convert|1/16|in|mm|adj=mid|-diameter|3}} hardened steel ball, and can be used on [[sheet metal]].
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| The B and C scales overlap, such that readings below HRC 20 and those above HRB 100, generally considered unreliable, need not be taken or specified.
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| ===Typical values=== | | ===Typical values=== |
