ISO 6506-2:2017

Overview

ISO 6506-2:2017 - "Metallic materials - Brinell hardness test - Part 2: Verification and calibration of testing machines" defines how to verify and calibrate Brinell hardness testing machines. It specifies direct and indirect verification methods, when each must be performed, and the required reporting. The standard applies to both fixed-location and portable Brinell hardness testers and supports traceability of results to the SI.

Key topics and technical requirements

• Direct verification (checks individual machine parameters):
  • Measurement of test forces (within ±1.0% of nominal force) using force-proving instruments (ISO 376 Class 1 or equivalent).
  • Measurement of indenter ball properties: diameter tolerances by ball size (e.g., 10 mm ±0.005 mm; 5 mm ±0.004 mm; smaller sizes also specified), hardness (tungsten‑carbide balls ≥ 1 500 HV) and density (~14.8 ±0.2 g/cm³).
  • Calibration of indentation-diameter measuring systems (diameter error ≤ 0.5%; projected-area systems ≤ 1%).
  • Verification of the testing cycle to conform with ISO 6506‑1 (temperature recommendation 23 ±5 °C).
  • Annex B provides modified procedures for machines that cannot meet the specified force–time profile.
• Indirect verification (checks overall machine performance):
  • Uses reference blocks calibrated per ISO 6506‑3.
  • For each force/ball size, five indentations are measured on at least two reference blocks and statistical checks (repeatability and error) are evaluated against tabulated permissible limits (see Tables 2 & 3 in the standard).
• Reporting and traceability:
  • Verification reports / calibration certificates must detail conditions (e.g., temperature), instruments used, uncertainties (Annex A), and conformance to tolerances.
• Independence of methods:
  • If a machine is used for multiple hardness methods, it must be verified separately for each method.

Applications and users

Who benefits:

• Calibration and metrology laboratories performing hardness machine certification
• Hardness testing machine manufacturers and service technicians
• Quality assurance and metallurgical labs in manufacturing, aerospace, automotive and materials testing
• Inspection bodies that require traceable Brinell measurements

Practical benefits:

• Ensures reliable, repeatable Brinell hardness results
• Supports accredited calibration and compliance with traceability requirements
• Reduces measurement uncertainty and nonconformances in material hardness testing

Related standards

• ISO 6506-1: Test method for Brinell hardness
• ISO 6506-3: Calibration of Brinell reference blocks
• ISO 376: Calibration of force-proving instruments
• ISO 6507-1: Vickers hardness test (related hardness method)

Keywords: ISO 6506-2, Brinell hardness test, verification and calibration, hardness testing machines, direct verification, indirect verification, reference blocks, indenter ball, calibration certificate, measurement traceability.