ISO 255:2023

Overview

ISO 255:2023 - "Belt drives - Pulleys for V‑belts (system based on datum width) - Geometrical inspection of grooves" - defines methods for the mechanical inspection of grooved pulleys designed for classical and narrow V‑belts using the datum‑width system. The standard describes the sequence of checks and the measuring tools and procedures used to verify groove regularity, geometry and run‑out. Inspection parameters and tolerances are referenced to related International Standards.

Key topics and technical requirements

• Scope and sequence of inspection
  • Four successive checks: groove profile, groove spacing, datum diameter, and run‑out (Clause 5).
• Groove profile
  • Profile dimensions (datum width, groove angle, height above and depth below datum) are specified in ISO 4183.
  • Use of limit gauges (min/max ends) to verify groove angle, datum width, groove height and groove depth (Clause 6). The “min” end checks minimum groove angle; the “max” end checks maximum angle and other profile parameters.
• Groove spacing
  • Nominal spacing e and permissible tolerances for multi‑groove pulleys are given (ISO 5291 referenced).
  • Measurement uses a groove spacing locator (vernier with interchangeable inspection balls). Measured spacing x minus ball diameter gives e (Clause 7).
• Datum diameter
  • Datum diameter definitions and permissible variations reference ISO 4183 and ISO 5291.
  • Inspection by placing two checking balls or rods in the groove and measuring distance K between tangent planes; datum diameter is obtained by: d_d = K − 2h_s (2h_s = corrective term) (Clause 8).
• Run‑out tolerances
  • Radial (t1) and axial (t2) circular run‑out limits are defined and must be checked against values in ISO 5291 (Clause 9).

Applications and users

ISO 255:2023 is intended for:

• Pulley and belt manufacturers - production control, acceptance testing and shop‑floor inspection.
• Quality and metrology labs - verifying conformity to geometrical specifications.
• Maintenance and reliability engineers - assessing pulley wear, alignment and replacement needs.
• Design engineers - ensuring component interchangeability and drive performance when specifying pulleys for V‑belt drives.

Practical benefits include consistent inspection methodology, improved belt‑pulley fit, reduced vibration and wear, and better production traceability.

Related standards

• ISO 4183 - groove and belt dimensions (vocabulary/profile data)
• ISO 5291 - multi‑groove spacing and inspection ball/rod specifications
• ISO 1081 - vocabulary for V‑belts and pulleys

Keywords: ISO 255:2023, belt drives, pulleys for V‑belts, geometrical inspection of grooves, datum width, groove profile, groove spacing, datum diameter, run‑out tolerances, limit gauge, groove spacing locator.