ISO 6336-2-2019 (2020) PDF

Full title and description

Calculation of load capacity of spur and helical gears — Part 2: Calculation of surface durability (pitting). This is the third edition, published by the International Organization for Standardization (ISO) as ISO 6336-2:2019 with a corrected version issued in 2020; it provides the formulae and procedures used to evaluate gear tooth surface durability (pitting) for cylindrical involute gears under typical lubrication and loading conditions.

Abstract

This part of ISO 6336 specifies the fundamental formulae for determining the surface load capacity (permissible contact stress) of cylindrical spur and helical gears with involute teeth. It covers influences on surface durability for which quantitative assessment is possible, and is intended primarily for oil‑lubricated transmissions (with approximate applicability to slow-running grease‑lubricated systems when mesh lubrication is adequate). The document clarifies limitations and points users to ISO 6336‑1 when the general conditions do not apply.

General information

• Status: Published / Current (confirmed edition).
• Publication date: 2019‑11 (published 26 November 2019); corrected version (English/French) November 2020.
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 21.200 (Gears).
• Edition / version: Edition 3 (ISO 6336‑2:2019), corrected 2020.
• Number of pages: 37.

Key bibliographic and lifecycle metadata (status, edition, page count and corrected‑version note) are recorded on the ISO catalogue entry for ISO 6336‑2:2019.

Scope

Specifies formulae and calculation procedures to determine surface load capacity (resistance to pitting) of cylindrical spur and helical gears with involute external or internal teeth. Applicable mainly to oil‑lubricated transmissions; can be used for slow grease‑lubricated transmissions given continuous mesh lubrication. Formulae apply to gears produced to the basic rack of ISO 53 and are valid where the actual transverse contact ratio is within the standard limits (practical use up to about εαn = 2.5). The standard does not address other surface damage modes (plastic yielding, scuffing, scratching, etc.) except where explicitly noted. For general principles and influence factors refer to ISO 6336‑1.

Key topics and requirements

• Definition and calculation of permissible contact stress (surface load capacity) for pitting assessment.
• Fundamental formulae for contact stress, Hertzian contact geometry, and stress correction factors that influence pitting life.
• Influence factors: surface roughness, lubricants and film thickness, contact geometry (curvatures), load‑sharing, alignment and manufacturing deviations, and operating temperature.
• Applicability limits (gear types, transverse contact ratio, material/heat‑treatment ranges) and explicit exclusions (certain wear/scuffing/plastic deformation phenomena).
• Prescribed approach to combine factors and derive allowable contact stress and safety margins for design/evaluation of gearsets.

These topics form the technical core used by designers to rate gear tooth surface durability and to compare design alternatives using a common, validated calculation framework.

Typical use and users

Primary users are experienced gear designers and mechanical engineers in gearbox and transmission design, manufacturing engineers concerned with heat treatment and surface preparation, test laboratories performing durability verification, academic researchers in tribology and gear mechanics, and standards committees or certifiers referencing gear rating procedures. ISO 6336 material is intended for users who can select and justify factor values (i.e., not for casual/novice use without gear design experience).

Related standards

ISO 6336‑2 is part of the ISO 6336 series on load capacity of spur and helical gears. Closely related documents include ISO 6336‑1 (Basic principles and general influence factors), ISO 6336‑3 (Tooth bending strength), ISO/TS 6336‑4 (Tooth flank fracture load capacity), ISO 6336‑5 (Strength and quality of materials) and ISO 6336‑6 (Service life under variable load). Several Technical Specifications in the 6336 family cover scuffing and other specific failure modes. Together these parts provide a complete framework for gear rating and service‑life calculations.

Keywords

Gears; spur gear; helical gear; load capacity; surface durability; pitting; contact stress; permissible contact stress; ISO 6336; gear rating; lubrication; Hertzian contact.

FAQ

Q: What is this standard?

A: ISO 6336‑2:2019 (third edition, corrected 2020) is the ISO standard that defines the methods and formulae for calculating surface durability (pitting) — i.e., the permissible contact stress — of cylindrical spur and helical gears.

Q: What does it cover?

A: It covers the calculation of surface load capacity (resistance to pitting) including contact stress calculations, Hertzian contact geometry, and a set of influence/factor corrections (surface condition, lubrication, geometry, etc.). It also states applicability limits and types of damage not covered.

Q: Who typically uses it?

A: Experienced gear designers, gearbox manufacturers, tribology researchers, materials and heat‑treatment engineers, and test laboratories use ISO 6336‑2 as part of gear rating and verification procedures; the ISO 6336 series is generally intended for users familiar with gear calculation practice.

Q: Is it current or superseded?

A: The cited edition is ISO 6336‑2:2019 (third edition) with a corrected version issued in November 2020; the ISO catalogue lists the 2019 edition as the current published text. Users should check the ISO catalogue or national adoption notices for any later amendments or revisions before use.

Q: Is it part of a series?

A: Yes — it is Part 2 of the ISO 6336 series. The series includes Part 1 (general principles), Part 3 (tooth bending strength), Part 4 (tooth flank fracture — TS), Part 5 (materials), Part 6 (service life under variable load) and additional technical specifications related to scuffing and special checks.

Q: What are the key keywords?

A: Pitting, contact stress, surface durability, gear rating, spur gear, helical gear, Hertzian contact, lubrication, ISO 6336.