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Definition: Rockwell hardness testing is a static indentation method in which the hardness is determined from the permanent indentation depth of an indenter under a defined preliminary and main load. The method is governed by DIN EN ISO 6508. Results are given in scales such as HRC or HRB.

Practical relevance: Rockwell testing is characterised by short testing times and direct readability. Different indenters (diamond cone or steel ball) allow various material ranges to be tested. It is frequently used to check hardened steels (HRC) or softer metals (HRB). Surface condition and specimen thickness influence the accuracy.

Decision-making perspectives:

• Technical decision-makers: Rapid checking of heat treatment results in series production.
• Purchasing/project management: Specification of required Rockwell hardness ranges in material requirements.
• Science: Comparison with Vickers or Brinell hardness values and conversion tables.
• Insurance/law: Documented hardness verification in the event of material deviations.

Typical testing or verification methods: Rockwell testing machine, calibration with reference hardness blocks, conversion tables in accordance with ISO standards.

FAQ:

• When is the HRC scale used?
• The HRC scale is mainly used for hardened or high-strength steels.

Definition: Roundness testing is the metrological determination of the deviation of a real circular cross-section from the ideal circular form. It assesses compliance with roundness tolerances in accordance with DIN EN ISO 12181. The analysis is carried out by recording profile points and comparing them with a reference geometry.

Practical relevance: Roundness deviations affect the running behaviour, tightness and wear of rotating components such as shafts, bearings or sealing surfaces. The maximum radial deviation within a defined tolerance zone is assessed. Measurements are carried out with roundness measuring instruments or high-precision coordinate measuring machines. Temperature, clamping condition and storage can influence the measurement result.

Decision-making perspectives:

• Technical decision-makers: Ensuring low-vibration rotation and minimal bearing load.
• Purchasing/project management: Clear definition of permissible roundness tolerances in drawings.
• Science: Analysis of manufacturing deviations and form parameters.
• Insurance/law: Verification of geometric deviations in the event of malfunctions.

Typical testing or verification methods: Roundness measuring instrument with rotary table, polar or Cartesian evaluation, comparison with GPS tolerance specifications.

FAQ:

• What is the difference between roundness and cylindricity?
• Roundness refers to a single cross-section, cylindricity to the entire lateral surface of a cylinder.