Overview
SIST ISO 6336-5:2018 - "Calculation of load capacity of spur and helical gears - Part 5: Strength and quality of materials" defines how material strength and quality influence gear load capacity. The standard describes contact (pitting) and tooth-root (bending) stresses, provides numerical values for the allowable (limit) stress numbers, and specifies requirements for material quality and heat treatment. Values in SIST ISO 6336-5:2018 are intended for use with the calculation methods in the ISO 6336 series and related application standards for industrial, high-speed and marine gears.
Key topics and technical requirements
- Allowable stress numbers: Numerical limit values for contact and bending stresses and guidance on determining them for given materials and conditions.
- Methods for determination: Two principal approaches are described:
- Method A - allowables derived from gear endurance tests matching the actual gear geometry and operating conditions.
- Method B - standard allowable stress numbers based on reference tests, pulsator and rolling-contact tests, and practical experience; includes quality classes ME, MQ and ML.
- Material quality and heat treatment: Requirements, inspection and the influence of processes (carburizing, nitriding, through-hardening, shot peening, etc.) on allowable stresses and hardness depth.
- Test and evaluation guidance: Recommendations on using gear and coupon tests, how to treat included process influences (e.g., lubrication, surface finish), and how to set influence factors when test data include certain effects.
- Scope of materials: Covers the most widely used ferrous gear materials and associated heat treatments; provides tables, graphs and annexes (e.g., hardening depth, core hardness coefficients) to support calculation.
- Conformance and limitations: Values are compatible with ISO 6336-2, -3, -6 and ISO 10300 procedures; results align with other methods within the scope of ISO 6336-1 and ISO 10300-1.
Practical applications and users
SIST ISO 6336-5:2018 is used by:
- Gear designers and mechanical engineers rating load capacity for spur and helical gears
- Materials and heat-treatment engineers specifying process and inspection criteria
- Quality and inspection teams applying material-quality classes (ME/MQ/ML)
- Manufacturers of industrial, high-speed and marine gear systems
- Engineers applying ISO 6336 calculation procedures and ISO 10300 bevel-gear ratings
Practical uses include selecting material/heat-treatment combinations, defining inspection and testing regimes, and providing input allowable stress numbers for pitting and bending calculations in gear design.
Related standards
