Standards guide

Vickers hardness testing per IS 1501, ASTM E92 and ISO 6507

Q: What is the difference between HV 10 and HV 30?

Only the test force: 10 kgf (98.07 N) against 30 kgf (294.2 N). Because Vickers impressions are geometrically similar, a homogeneous steel gives practically the same number at both. HV 30 makes a larger indent that is easier to measure and averages more microstructure; HV 10 is chosen for smaller or thinner parts. Always write the force after the number.

Q: Can Vickers test a 0.3 mm sheet?

Yes. The rule is thickness at least 1.5 times the diagonal, so on 0.3 mm sheet the diagonal must stay below 0.2 mm. For a 200 HV steel that means HV 3 or lower (d about 0.17 mm); for a 600 HV spring steel HV 5 still works (d about 0.12 mm). Check the back face for any visible bulge, which would invalidate the result.

Q: Why is my HV higher than my Rockwell-converted value?

Usually because the two tests sample different depths. A Rockwell C indent penetrates far deeper than a low-force Vickers indent, so on a case-hardened or shallow-quenched part it averages in softer core material and reads low, while the Vickers indent sits entirely in the hard skin. Polishing for Vickers also removes any decarburised layer, and ASTM E140 conversions are approximate and apply only to specific steel groups.

Q: Do I need a microscope or a camera?

The standards accept either, provided the measuring system is verified against a stage micrometer at each magnification. A filar eyepiece is adequate for occasional macro work. A camera with measuring software removes operator judgement of the indent corners, stores the image with every result, and is practically essential for case-depth traverses and weld profiles with dozens of indents per specimen.

Q: How often must the Vickers tester be verified?

Indirect verification with certified reference blocks at least every 12 months, and again after the machine is moved, repaired or the indenter changed. Direct verification of force, indenter and measuring system is required at installation and whenever indirect verification fails. In addition, IS 1501 Part 2 and ISO 6507-2 expect a routine check on a reference block every day the machine is used.

Q: Which force should I use for case-depth measurement?

HV 1 (9.807 N) is the conventional scale: ISO 2639 defines effective case depth as the distance from the surface to where hardness falls to 550 HV 1, and IS 6416 describes the Indian methods. HV 1 indents are small enough to space at 3 d intervals through a case of a few tenths of a millimetre yet large enough to measure reliably.

One diamond pyramid, one formula, and a force range that runs from 10 gf to 100 kgf. Vickers is the method you reach for when the part is thin, the layer is shallow or the material is too hard for anything else. Here is what the standards actually require.

By Eklavya Techno Solutions engineering teamUpdated 21 September 20268 min read

Definition: The Vickers hardness test (IS 1501, ASTM E92, ISO 6507) presses a square-based diamond pyramid with a 136° angle between opposite faces into the test surface under a fixed force, and the Vickers hardness number HV is the test force divided by the sloping surface area of the indentation, calculated from the mean of the two measured diagonals.

1. The Vickers principle and the HV formula

The indenter is a square-based diamond pyramid with 136° between opposite faces. Under the test force F it leaves a square impression whose two diagonals are measured and averaged to d. Hardness is the force per unit sloping area of the impression:

HV = 0.1891 × F / d² (F in N, d in mm) or HV = 1.8544 × F / d² (F in kgf, d in mm)

Example: a 30 kgf (294.2 N) test gives a mean diagonal of 0.527 mm, so HV = 1.8544 × 30 / 0.527² = 200, written 200 HV 30. A dwell outside 10–15 s is appended, e.g. 200 HV 30/20.

Because all Vickers impressions are geometrically similar, the number is in principle independent of force: 640 HV 30 should read close to 640 HV 10. Rockwell scales and Brinell F/D² ratios have no such freedom. The independence weakens below about HV 0.2, where the indentation-size effect and measurement uncertainty push readings upward, so the force is always stated. The impression is only about one-seventh of the diagonal deep, which is what suits Vickers to thin sections and surface layers.

2. Force ranges: macro, low-force and micro

IS 1501 (Part 1), ASTM E92 and ISO 6507-1 divide the method into three ranges. The designation states the nominal force in kgf: HV 30 means 30 kgf, i.e. 294.2 N.

Vickers force ranges per IS 1501 / ISO 6507-1, with typical applications
Range	Designation	Force (kgf)	Force (N)	Typical use
Macro (conventional)	HV 5 to HV 100	5 to 100	49.03 to 980.7	Bulk metals, heat-treated parts, weld cross-sections, tool steel, carbide
Low-force	HV 0.2 to < HV 5	0.2 to < 5	1.961 to < 49.03	Thin sheet, case-depth traverses (usually HV 1), small parts, HAZ profiles
Micro	< HV 0.2	0.01 to < 0.2	0.09807 to < 1.961	Coatings, individual phases, decarburised skins, ceramics

Use the largest force the specimen will take; a bigger impression is easier to measure and averages out microstructure. HV 30 is the general-purpose scale for steel, HV 10 for smaller parts, HV 1 for case-depth traverses and HV 0.05 to HV 0.1 for plated layers.

A result is only comparable with another if the force is quoted. "640 HV" without the force is incomplete.

3. Test conditions: dwell, thickness, spacing and surface

Testing cycle. Force applied without shock in 2–8 s and held for 10–15 s; a longer dwell must be reported. Test at 10–35 °C, preferably 23 ± 5 °C.
Minimum thickness. At least 1.5 × the mean diagonal, with no deformation visible on the back face. Thin material simply means a lower force.
Spacing. Per ISO 6507-1 the indent centre must be at least 2.5 d from the edge for steel, copper and copper alloys and 3 d for light metals, lead and tin; adjacent indents at least 3 d apart (steel, copper) or 6 d (light metals). ASTM E92 uses 2.5 d as its general minimum; closer indents sit in the work-hardened zone of the previous one and read high.
Surface finish. Flat, clean and finished so the diagonal ends are clearly defined: fine ground for HV 5 and above, polished for low-force and micro work, without heating or cold-working the surface.
Indent quality. The two diagonals should not differ by more than 5 %; a larger difference (anisotropy or tilt) is reported. ISO 6507-1 does not recommend diagonals below 0.020 mm (20 µm) because measurement uncertainty then dominates.

4. Measuring the diagonals: magnification and uncertainty

HV varies with 1/d², so any error in the diagonal is doubled in the hardness. A ±0.5 µm measurement error is negligible on a 500 µm macro indent (±0.2 % in HV) but is about ±3.3 % in HV on a 30 µm micro indent, before operator judgement of the corner is added; hence the 20 µm floor and the advice to use the highest usable force. Choose the objective so the impression fills a quarter to three-quarters of the field of view (ASTM E92/E384 guidance): about 10× for HV 30 on steel, 20–40× for HV 1 to HV 5, 50–100× for HV 0.05 to HV 0.2. Camera measurement removes the corner-location variable and stores the image with the result, which matters for audits and long traverses.

5. Where Vickers is the right method

Thin sheet, strip and foil that fail the Rockwell thickness rule, tested at HV 1 to HV 5.
Case-hardened, carburised and nitrided layers. A row of HV 1 indents from the surface inward gives the profile; the depth where it crosses 550 HV 1 is the effective case depth in ISO 2639, and IS 6416 covers the Indian methods.
Coatings and platings (hard chrome, electroless nickel, PVD) in the micro range, on a taper section or directly if at least 1.5 d thick.
Welds. An HV 5 or HV 10 traverse across parent metal, HAZ and weld metal checks for hard zones.
Very hard materials. Cemented carbide (1300–1800 HV), boronised surfaces, ceramics and glass are beyond the Brinell ball and the Rockwell C scale; the diamond pyramid handles them at HV 30 to HV 50.

6. Vickers vs Knoop, and Vickers vs Rockwell C

Knoop (ASTM E92, ISO 4545) uses an elongated rhombic diamond (172°30′ and 130°) and measures only the long diagonal. The impression is about 2.8 times longer than a Vickers indent at the same force and only one-thirtieth as deep as it is long (one-seventh for Vickers), so Knoop suits very thin coatings and brittle ceramics that crack around a Vickers indent. Against that, HK is not independent of force and has few conversion data, so Vickers remains the default unless a specification calls for Knoop.

Rockwell C on tool steel is faster and needs no optics; Vickers takes over when the part is too small or thin or a profile is needed. Conversion is approximate: ASTM E140 Table 1 for non-austenitic steels gives 60 HRC ≈ 697 HV, 55 HRC ≈ 595 HV, 50 HRC ≈ 513 HV and 40 HRC ≈ 392 HV, but these are fits for specific steel families and ISO 18265 warns against using converted values for acceptance unless agreed between the parties. Our conversion guide has the tables.

7. Verifying the machine per IS 1501 Part 2 / ISO 6507-2

Direct verification checks each element separately, at installation, after repair, and when indirect verification fails:

Test force: within ±1.0 % of nominal for HV 0.2 and above, ±1.5 % below HV 0.2.
Indenter: polished, defect-free faces meeting at a point; angle between opposite faces 136° ± 0.5°; pyramid axis within 0.5° of the loading axis.
Measuring system: checked against a certified stage micrometer at every objective used.
Testing cycle: approach, application and dwell times within Section 3 values.

Indirect verification treats the machine as a whole: for each force in use, at least two certified reference blocks of different hardness are indented five times each. Repeatability is the spread of the five diagonals as a percentage of their mean; error is the difference between the mean measured hardness and the certified value. In the macro range the permitted repeatability is 2 % of the mean diagonal for blocks of 225 HV and above (3 % below) and the error must be within ±3 %; low-force and micro limits are wider. It is repeated at intervals not exceeding 12 months and after any move or indenter change, and a routine check on a reference block is made each day the machine is used. Blocks are calibrated per IS 1501 (Part 3) / ISO 6507-3; see our test block guide.

A camera system needs its pixel scale verified at every magnification; ask for the stage-micrometer check in the calibration report.

8. Sample preparation checklist

Section with a coolant-fed abrasive cut-off, never a torch or dry grinder.
Mount small specimens in resin so the face is flat and perpendicular; hot-mounting that tempers hardened steel gives low readings.
Grind, then polish: 600–1200 grit for HV 5 and above, 1 µm diamond for low-force and micro work.
Remove decarburised or scaled skin for bulk hardness; for case depth, prepare a true cross-section with a sharp edge.
Seat the specimen so it cannot rock, confirm squareness with a trial indent, and run a reference-block check before the first result of the day.

Frequently asked questions

What is the difference between HV 10 and HV 30?

Only the test force: 10 kgf (98.07 N) against 30 kgf (294.2 N). Because Vickers impressions are geometrically similar, a homogeneous steel gives practically the same number at both. HV 30 makes a larger indent that is easier to measure and averages more microstructure; HV 10 is chosen for smaller or thinner parts. Always write the force after the number.

Can Vickers test a 0.3 mm sheet?

Yes. The rule is thickness at least 1.5 times the diagonal, so on 0.3 mm sheet the diagonal must stay below 0.2 mm. For a 200 HV steel that means HV 3 or lower (d about 0.17 mm); for a 600 HV spring steel HV 5 still works (d about 0.12 mm). Check the back face for any visible bulge, which would invalidate the result.

Why is my HV higher than my Rockwell-converted value?

Usually because the two tests sample different depths. A Rockwell C indent penetrates far deeper than a low-force Vickers indent, so on a case-hardened or shallow-quenched part it averages in softer core material and reads low, while the Vickers indent sits entirely in the hard skin. Polishing for Vickers also removes any decarburised layer, and ASTM E140 conversions are approximate and apply only to specific steel groups.

Do I need a microscope or a camera?

The standards accept either, provided the measuring system is verified against a stage micrometer at each magnification. A filar eyepiece is adequate for occasional macro work. A camera with measuring software removes operator judgement of the indent corners, stores the image with every result, and is practically essential for case-depth traverses and weld profiles with dozens of indents per specimen.

How often must the Vickers tester be verified?

Indirect verification with certified reference blocks at least every 12 months, and again after the machine is moved, repaired or the indenter changed. Direct verification of force, indenter and measuring system is required at installation and whenever indirect verification fails. In addition, IS 1501 Part 2 and ISO 6507-2 expect a routine check on a reference block every day the machine is used.

Which force should I use for case-depth measurement?

HV 1 (9.807 N) is the conventional scale: ISO 2639 defines effective case depth as the distance from the surface to where hardness falls to 550 HV 1, and IS 6416 describes the Indian methods. HV 1 indents are small enough to space at 3 d intervals through a case of a few tenths of a millimetre yet large enough to measure reliably.

Which ETS machine

ETS VM 50-TSPCTouch-screen PC Vickers tester, 1 to 50 kgf, with camera-based diagonal measurement for HV 1 case-depth traverses through to HV 50 on carbide; built to IS 1501-2, ASTM E92 and ISO 6507-2.
VcB-250 optical Vickers cum BrinellOne machine for Vickers and Brinell on bulk components, castings and heat-treated parts, to IS 1501-2 and IS 1500-2.
RASN-TSFA and RSNE-TFor production Rockwell C checks on tool steel and hardened parts where speed matters more than a hardness profile.
Vickers indenters, reference blocks and microscopesCertified 136° diamond indenters and HV test blocks for daily checks and indirect verification.
All Vickers hardness testersOptical and PC-based Vickers models, plus camera retrofits for existing testers; installation, training and calibration support from Ichalkaranji.

Need help choosing? Tell our engineers what you test — material, size, standard and volume — and we will recommend a machine, scales and test blocks from our range.

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