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 Rockwell F-Scale Hardness 1/16 inch diamond ball, 60 kgf load
Symbol:  HRF

The Rockwell Hardness Test presses a steel or diamond hemisphere-conical penetrator against a test specimen and measures the resulting indentation depth as a gage of the specimen hardness. The harder the material, the higher the HR reading.

In the test, a minor load (10 kgf) is first applied, and the test dial (measuring the indention depth) is reset to zero. Then a major load (60, 100, or 150 kgf) is applied to create the full indention. The major load is reduced back to the minor load, and the indention depth measurement is taken.

The penetrator is usually 1/16 inch in diameter, although larger diameters (such as 1/8 inch) may be used for softer metals. Choosing the proper penetrator and the corresponding load requires experience. Some commonly used combinations are summarized below:

 Scale Condition Application A Brale indenter60 kgf load Thin, hard sheet materials, such as tungsten carbide. B 1/16 in diamond ball100 kgf load Medium/low hard materials, such as annealed carbon steels. C Brale indenter150 kgf load Materials harder than HRB 100. D Brale indenter100 kgf load Case-hardened materials. F 1/16 inch Brale indenter60 kgf load Soft materials, such as bearing metals. N 1/16 inch Superficial Brale indenter15, 30, or 45 kgf load Unhardened materials, such as metals softer than hardened steel or hard alloys, or where shallow indentations are desired. T 1/16 inch diamond ball15, 30, or 45 kgf load Unhardened materials, such as metals softer than hardened steel, or where shallow indentations are desired.

 Convert   HRF        (suggested range: 88 ~ 100)
 HRF   94   approximately* = Hardness Symbol Amount Name SuggestedRange HB (3000) 110 Brinell 10 mm Standard 3000 kgf 80~445 HB (500) 102 Brinell 10 mm Standard 500 kgf 89~189 HB (Tungsten 3000) 110 Brinell 10 mm Tungsten 3000 kgf 80~620 HB (Indentation) 5.56 mm Brinell Indentation 6~2 HK 130 Knoop 97~920 HM 2.5 Mohs 1~10 HRA << Rockwell A-Scale 59~86 HRB 65 Rockwell B-Scale 41~100 HRC << Rockwell C-Scale 19~69 HRD << Rockwell D-Scale 39~77 HR-15N << Rockwell Superficial 15N 69~94 HR-15T 82 Rockwell Superficial 15T 77~93 HR-30N << Rockwell Superficial 30N 41~85 HR-30T 60 Rockwell Superficial 30T 53~82 HR-45N << Rockwell Superficial 45N 19~76 HR-45T 38 Rockwell Superficial 45T 28~71 HS 18 Shore Scleroscope 17~97 Approx. TS 383 MPa Tensile Strength (Approx.) 390~2450 HV 116 Vickers 20~1800

 Legend << The hardness value is below the acceptable range of the particular hardness scale. >> The hardness value is above the acceptable range of the particular hardness scale. ### The hardness value is near the limit (within 15%) of the acceptable range of the particular hardness scale. * The many hardness tests listed here measure hardness under different experimental conditions (e.g. indenters made in different sizes, shapes, and materials, and applied with different loads) and reduce their data using different formulae. As a result, there is NO direct analytic conversion between hardness measures. Instead, one must correlate test results across the multiple hardness tests. This calculator is based on hardness data compiled from ASM Metals Reference Book 3rd ed, published by ASM International, and Machinery's Handbook 25th ed, published by Industrial Press. The calculator curve-fits multiple hardness data onto a common polynomial basis and then performs an analytic conversion. The accuracy of the conversion depends on the accuracy of the provided data and the resulting curve-fits, and on the valid ranges spanned by the different hardness tests. Converted hardness values should be used for comparative purposes only.