ISO 6336-5:2016

Overview

ISO 6336-5:2016 - "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 ISO 6336-5:2016 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

ISO 6336-5:2016 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

• ISO 6336 series: ISO 6336‑1, -2, -3, -6 (calculation framework for gear load capacity)
• ISO 10300 (bevel gear rating)
• Normative references used by ISO 6336‑5: ISO 642, ISO 643, ISO 683 series, ISO 2639 and other material/inspection standards.