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Rubber Shore Hardness Scales

24 Oct 2019 | Posted by Andrew Onions

Elastomeric materials are usually measured with either a Shore A Scale Durometer or an IRHD dead load system. These tests are designed for use with samples approximately 6mm thick, and a surface area sufficient to permit at least 3 test points 5mm apart and 13mm from the edge of the material.

Measuring Shore A – D, 0 and 00

The method for measuring Shore hardness’s is through a spring loaded indentation device, on which values are obtained as a function of the viscoelastic property of the material. The cone indenter extends 2.5mm from the base plate and is pressed onto the sample material, generating resistance against an 822g spring. Each 0.0254 mm of deflection of the indenter is shown as 1 degree Shore (A), therefore, the harder the material, the more the deflection, the higher the number.

Measuring IRHD (International Rubber Hardness Degrees)

The method for measuring IRHD hardness’s is through an instrument with a spherical indenter which indents the sample under a minor and major Load. The differential indentation depth is measured and tabulated to read directly in “IRHD” degrees. The displacement / IRHD degrees conversion table is published in ISO 48 : 1994. The standard shows three different combinations of Ball & Loadings, (N) Normal, (H) High and (L) Low.

Shore 00

ASTM D 2240

Shore 0

ASTM D 2240

Shore A

DIN 53505

Shore D

DIN 53505

IRHD

ASTM 1415

 

 

100

58

100

 

 

95

46

95

 

 

90

39

90

 

 

85

33

85

98

84

80

29

80

97

79

75

25

74

95

75

70

22

68

94

72

65

19

64

93

69

60

16

62

91

65

55

14

54

90

61

50

12

49

88

57

45

10

44

86

53

40

8

39

83

48

35

7

35

80

42

30

6

28

76

35

25

 

 

70

28

20

 

 

63

21

15

 

 

55

14

10

 

 

45

8

5

 

 

Medium and Low Density Cellular Elastomers, Urethane Foam & Cork

Medium Density Cellular and Solid Elastomers

Solid and Cellular Elastomers

Polyurethanes, PTFE rigid, Thermoplastic and Elastomeric, very hard

Solid Elastomers


You can download this chart by clicking here