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Rockwell Round Correction Charts- Reference Information and Standards -

"Round correction" is another overlooked factor in hardness testing. Inexperienced untrained

operators are using a sophisticated piece of equipment that is calibrated and they expect it to

give good results no matter what the condistions. But users actually need to know what they

are doing. Round correction is just like testing close to the edge of a sample -- the material

flows more easily to the edge and, in effect, creates a lower hardness value. There is no

correction factor for testing close to an edge but there is for rounds; Use the values below to

add to your test results depending on the diameter and result. And just like with testing close

to an edge, check your vee anvil alignment with the indenter. If it is off by a fraction it could

affect your results by a large amount or break a diamond indenter.

ROCKWELL C, A, D SCALES

Diameter .25" .375" 0.5" .625" .75" .875" 1" 1.25" 1.5"

Result 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 --

60 1.5 1.0 1.0 0.5 0.5 0.5 0.5 -- --

65 1.5 1.0 1.0 0.5 0.5 0.5 0.5 -- --

70 1.0 1.0 0.5 0.5 0.5 0.5 0.5 -- --

75 1.0 0.5 0.5 0.5 0.5 0.5 -- -- --

80 0.5 0.5 0.5 0.5 0.5 -- -- -- --

85 0.5 0.5 0.5 -- -- -- -- -- --

90 0.5 -- -- -- -- -- -- -- --

ROCKWELL B, F, G SCALES

Diameter .25" .375" 0.5" .625" .75" .875" 1"

Result 6.4 mm 10 mm 13 mm 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

ROCKWELL 15N, 30N, 45N SCALES

Rockwell Hardness Chart (plus a PDF)

(aka Hardness Scale Conversion Chart)

Round Correction Factor

Hardness Minimum Thickness

ASTM Hardness Test Methods

Rockwell Hardness Scales

Brinell Hardness Chart (plus a PDF)

Rockwell Hardness Testing

Brinell Hardness Testing

Microhardness Testing

Rockwell Round Correction Charts http://www.qs-hardnesstester.com/Hardness-Round-Correction.html

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Diameter .125" .25" .375" .5" .75" 1"

Value 3.2 mm 6.4 mm 10 mm 13 mm 19 mm 25 mm

20 6.0 3.0 2.0 1.5 1.5 1.5

25 5.5 3.0 2.0 1.5 1.5 1.0

30 5.5 3.0 2.0 1.5 1.0 1.0

35 5.0 2.5 2.0 1.5 1.0 1.0

40 4.5 2.5 1.5 1.5 1.0 1.0

45 4.0 2.0 1.5 1.0 1.0 1.0

50 3.5 2.0 1.5 1.0 1.0 0.5

55 3.5 2.0 1.5 1.0 0.5 0.5

60 3.0 1.5 1.0 1.0 0.5 0.5

65 2.5 1.5 1.0 0.5 0.5 0.5

70 2.0 1.0 1.0 0.5 0.5 0.5

75 1.5 1.0 0.5 0.5 0.5 0

80 1.0 0.5 0.5 0.5 0 0

85 0.5 0.5 0.5 0.5 0 0

90 0 0 0 0 0 0

ROCKWELL 15T, 30T, 45T SCALES

Diameter .125" .25" .375" .5" .625" .75" 1"

Value 3.2 mm 6.4 mm 10 mm 13 mm 16 mm 19 mm 25 mm

20 13.0 9.0 6.0 4.5 4.5 3.0 2.0

30 11.5 7.5 5.0 3.5 3.5 2.5 2.0

40 10.0 6.5 4.5 3.5 3.0 2.5 2.0

50 8.5 5.5 4.0 3.0 2.5 2.0 1.5

60 6.5 4.5 3.0 2.5 2.0 1.5 1.5

70 5.0 3.5 2.5 2.0 1.5 1.0 1.0

80 3.0 2.0 1.5 1.5 1.0 1 0.5

90 1.5 1 1 0.5 0.5 0.5 0.5

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Rockwell Round Correction Charts http://www.qs-hardnesstester.com/Hardness-Round-Correction.html

2 of 2 2/26/2015 12:56 PM