Overview
SIST ISO 1328-2:2023 - "Cylindrical gears - ISO system of flank tolerance classification - Part 2" defines a classification system and allowable values for double flank radial composite deviations of individual cylindrical involute gears and sector gears. The standard covers definitions, the structure of the flank tolerance classes (R30 to R50), and the formulae used to calculate tolerances when a product gear is measured in double flank contact with a master gear. It applies to unassembled gears with three or more teeth and reference diameters up to 600 mm. Note: tolerance tables are not included and the standard does not provide gear design guidance or recommend specific tolerances.
Key topics and technical requirements
- Double flank test: measurement method where a master gear and product gear are rotated in tight mesh while changes in center distance are recorded.
- Deviations defined:
- Tooth-to-tooth radial composite deviation (f_id) - greatest change in center distance within any single pitch.
- Total radial composite deviation (F_id) - difference between maximum and minimum center distances across all teeth.
- Tolerance classes: The standard uses a unique set of classes (R30–R50). A gear specified to a class must meet both the total and tooth-to-tooth tolerance requirements.
- Formulae: Clause 5 provides formulae to compute allowable tolerances for individual product gears when mated with a master gear; no numeric tolerance tables are provided.
- Measurement controls:
- Use of a calibrated double flank test rig and an agreed master gear.
- Specification of datum surfaces for inspection (see ISO/TR 10064‑3).
- Considerations for equipment verification, uncertainty, filtering and data density.
- Applicability: Primarily for parallel-axis cylindrical gears; application to others (racks, worms, bevels) requires mutual agreement and adapted procedures.
- Annexes: Informative annexes include graphs (A), composite deviation over segments (B), reasons for class changes (C), conversion from other specifications (D), and calculation examples (E).
Practical applications and users
SIST ISO 1328-2:2023 is used by:
- Gear manufacturers for final inspection and quality classification of cylindrical and sector gears.
- Metrology and inspection labs performing double flank testing and reporting compliance.
- Quality engineers and procurement/specification writers who define acceptance criteria and tolerance classes in contracts.
- Maintenance and manufacturing process engineers who need to control tooth thickness and total radial composite effects.
Note: While useful for quality control and acceptance, the standard is not a design manual - designers should not use it to derive gear geometry or recommend application-specific tolerances.
Related standards
Keywords: SIST ISO 1328-2:2023, double flank radial composite deviations, cylindrical gears, flank tolerance classification, tooth-to-tooth radial composite deviation, total radial composite deviation, master gear, double flank test, gear inspection, gear manufacturing tolerances.
