Hardness Scales Compared: Leeb, Brinell, Rockwell and Vickers

Leeb (HL)

An impact body strikes the surface with fixed energy; the ratio of rebound velocity to impact velocity gives the value. Portable and usable on site, suitable for large workpieces and in-service equipment. The trade-off is sensitivity to surface condition and thickness – you need enough section and a clean surface.

Brinell (HB)

A 10 mm carbide ball is pressed into the surface under 3000 kgf, held, then released; load divided by indentation area gives the value. Large indentation, good representation, suitable for castings and forgings with coarse structure. Not suitable for finished surfaces.

Rockwell (HR)

A diamond cone or steel ball is pressed under a defined load, and indentation depth gives the value. Three common scales:

HRA – 60 kgf with a diamond cone, for hard alloys and similar very hard materials.

HRB – 100 kgf with a 1.588 mm steel ball, for annealed steel, cast iron and softer materials.

HRC – 150 kgf with a diamond cone, for hardened steel.

Rockwell is fast, leaves a small mark and is the workshop standard. But above roughly 450 HB, or on very small specimens, Rockwell is the only practical option.

Vickers (HV)

A diamond pyramid with a 136 degree included angle, typically 1 to 100 kgf, load divided by indentation surface area. The indentation is a clean square, so it works from very soft to very hard, and it is the standard method for laboratory work and for thin or case-hardened layers.

Other scales

Knoop (HK) for materials above roughly 1000 HV; Webster (HW) mainly for aluminium alloys; Shore (HS) for rubber and plastics; Barcol and Mohs in their own niches.

How to choose

Three questions: how big is the part and can it be moved; what material and hardness range; is a mark acceptable. Large parts on site – Leeb. Castings and forgings – Brinell. Finished parts – Rockwell. Thin layers and laboratory work – Vickers.

Conversions between scales are approximations. Always state the scale used in the report.