Rockwell Blocks

Diameter

Nominal Hardness Values

Variation

NIST Traceable

HRA

64mm

56, 65, 71, 75, 78, 81, 83, 85, 87

+/-0.3

No

HRB 

64mm

32, 42, 52

+/-0.5

No

HRB

64mm

62, 72, 82, 90, 95, 100

+/-0.4

No

HRC

64mm

10, 20, 25, 30, 35, 40

+/-0.15

Yes

HRC

64mm

45, 50, 55, 60, 62, 64, 67, 70

+/-0.1

Yes

HR15N

64mm

75, 80, 85, 87, 90, 92

+/-0.45

No

HR30N

64mm

41, 50, 60, 67, 73, 78, 81, 83

+/-0.5

No

HR15T

64mm

78, 82, 87

+/-0.5

No

HR30T

64mm

32, 42, 52, 62, 72, 78

+/-0.5

No

HRE

64mm

90

+/-0.5

No

HRL

64mm

92, 118

+/-0.5

No

HRM

64mm

67, 107

+/-0.5

No

HRR

64mm

105, 123

+/-0.5

No

HRC

51mm

20, 25, 30, 35, 40, 45

+/-0.15

No

HRC 

51mm

50, 55, 60, 62, 64, 67

+/-0.5

No

HBW30

115mm

150, 180, 200, 229, 250, 300, 350
400, 450, 500, 550, 600

+/-0.7%

No

HBW5 

115mm

100, 125

+/-0.7%

No