ISO 48-8:2018

Overview

ISO 48-8:2018 specifies a standardized method for measuring the apparent hardness of vulcanized or thermoplastic rubber roller covers using the Pusey and Jones method. The result is reported as the Pusey and Jones indentation value, an inverse hardness measurement (the harder the rubber, the lower the indentation value). The method uses a Pusey and Jones plastometer to measure indentation depth of a steel ball under a defined force.

Key topics and technical requirements

• Test principle: Depth of indentation of a 3.175 mm diameter steel ball under a force of 9.8 N (mass 1 000 ± 2 g) measured with a depth indicator.
• Apparatus: Pusey and Jones plastometer comprising supporting frame, polished steel ball indentor, calibrated mass, depth indicator (graduated 0.01 mm, range ≥ 3 mm) and specimen holder (clamp to stabilize roller).
• Procedure highlights:
  • Roller axis horizontal and test area uppermost.
  • Lower indentor until gauge needle makes three revolutions, set dial to zero.
  • Apply mass and read indentation after 60 s.
  • Make three measurements per test area at points at least 6 mm apart.
  • Report the median of three readings to the nearest whole number as the Pusey and Jones indentation value (expressed in hundredths of a millimetre).
• Conditioning and timing: Tests carried out ≥16 hours after vulcanization/finished grinding; for arbitration purposes ≥72 hours. Conditioning and test temperature per ISO 23529; maintain temperature equilibrium where possible.
• Calibration: Apparatus calibration is mandatory. Annex A gives a calibration schedule; laboratories should follow ISO 18899 guidance for verification frequency and procedures.
• Test report requirements: Full roller description, reference to ISO 48-8:2018, conditioning and test temperatures, individual results, number of areas tested, and date.

Applications

• Quality control and specification of rubber-covered rollers used in printing, laminating, conveying, and converting industries.
• Factory process control to monitor roller cover hardness after vulcanization or finishing.
• Comparative testing of roller coverings where apparent hardness (in-situ on the finished roller) is the critical functional parameter.
• Arbitration and acceptance testing when contract or industry specifications reference the Pusey and Jones method.

Who should use this standard

• Test laboratories performing rubber hardness tests on finished rollers.
• Manufacturers of rubber-covered rollers and roller-covering materials.
• Quality engineers and R&D teams concerned with roller performance (traction, nip pressure, surface contact).
• Procurement and inspection personnel specifying or verifying roller cover hardness.

Related standards

• ISO 48-2 - International rubber hardness test methods (different measurement principle).
• ISO 23529 - Conditioning and preparation of test pieces.
• ISO 18899 - Guide to calibration of test equipment.
• ISO 6123-1 - Requirements for hardness of rubber- or plastic-covered rollers.

Keywords: ISO 48-8, Pusey and Jones, apparent hardness, rubber-covered rollers, hardness test, plastometer, Pusey and Jones indentation value, roller cover hardness.