ISO TS 6336-4-2019 PDF

Full title and description

Calculation of load capacity of spur and helical gears — Part 4: Calculation of tooth flank fracture load capacity (ISO/TS 6336-4:2019). This Technical Specification provides a procedure to calculate the tooth flank fracture load capacity for cylindrical external spur and helical gears, with formulae validated for case‑carburized gears within defined geometric and material limits.

Abstract

This document describes a calculation procedure for tooth flank fracture (contact‑fatigue fracture) load capacity of cylindrical spur and helical gears with external teeth. It is not intended as a gearbox rating or certification method. The formulae apply to gears with tooth profiles in accordance with the basic rack of ISO 53 and are validated for case‑carburized gears within specified Hertzian stress, reduced radius of curvature and case hardening depth ranges.

General information

• Status: Published.
• Publication date: 30 January 2019 (Edition 1). Corrected English version issued July 2019.
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 21.200 (Gears).
• Edition / version: Edition 1 (2019).
• Number of pages: 29 (ISO published record).

Scope

Defines a method to calculate tooth flank fracture load capacity for external cylindrical spur and helical gears. The procedure is applicable to driving and driven gears whose profiles conform to the basic rack in ISO 53 and may be used where the transverse contact ratio εα < 2.5. The method was validated for case‑carburized gears and is limited to those gears satisfying the document’s specified ranges for Hertzian contact stress, normal reduced radius of curvature and case hardening depth; it does not cover other types of gear tooth damage. It is explicitly not intended as a gearbox rating method for certification.

Key topics and requirements

• Procedure and formulae for calculating tooth flank fracture (contact‑fatigue fracture) load capacity for cylindrical spur and helical gears.
• Applicability limited to case‑carburized gears with validated ranges: Hertzian stress approx. 500–3 000 N/mm²; reduced normal radius of curvature 5–150 mm; case hardening depth (at 550 HV, finished) 0.3–4.5 mm.
• Assumes tooth profiles conform to the basic rack of ISO 53; can be used for conjugate profiles when transverse contact ratio εα < 2.5.
• Notes limitations — not applicable to other tooth damage modes (e.g., pitting, scuffing, micropitting) and not intended as a gearbox certification/rating standard.
• References and cross‑links to other parts of ISO 6336 and related gear standards for complementary calculations and material/quality specifications.

Typical use and users

Used by gear designers and engineers performing strength assessments of involute spur and helical gears (especially case‑carburized gears), gearbox technical specialists who need tooth‑fracture‑specific calculations, researchers validating gear fatigue models, testing laboratories, and standards committees. It is intended for competent gear design professionals familiar with ISO 6336 methods and with the selection of appropriate influence factors.

Related standards

Part of the ISO 6336 family of documents on gear load capacity calculations. Closely related parts include ISO 6336‑1 (basic principles and influence factors), ISO 6336‑2 (surface durability / pitting), ISO 6336‑3 (tooth bending strength), ISO 6336‑5 (materials and quality) and ISO 6336‑6 (service life under variable load). Other related technical specifications and TRs in the 6336 series cover scuffing, micropitting and calculation examples. National adoptions and PD/BS/GB equivalents also exist.

Keywords

tooth flank fracture; contact fatigue; spur gears; helical gears; case‑carburized gears; Hertzian stress; reduced radius of curvature; case hardening depth; ISO 6336; ISO 53; gear load capacity.

FAQ

Q: What is this standard?

A: ISO/TS 6336‑4:2019 is a Technical Specification that defines a calculation procedure for the tooth flank fracture load capacity of external cylindrical spur and helical gears (case‑carburized gears in the validated parameter ranges).

Q: What does it cover?

A: It covers formulae and a calculation procedure for assessing tooth flank fracture (contact‑fatigue fracture) load capacity, assumptions on tooth profile (ISO 53 basic rack), and limits on materials and geometry where the method was validated (Hertzian stress, reduced radius, case hardening depth). It does not provide a full gearbox rating method and is not applicable to other tooth damage types.

Q: Who typically uses it?

A: Experienced gear designers, fatigue analysts, gearbox engineers, test laboratories, researchers and standards bodies working on gear strength assessments—especially when tooth‑fracture (flank fracture) risk needs explicit evaluation.

Q: Is it current or superseded?

A: As published by ISO, ISO/TS 6336‑4 was issued in January 2019 (corrected English version July 2019) and is recorded as a published Technical Specification. ISO’s record indicates the document is under the normal review lifecycle for standards; consult the ISO catalogue or your national standards body for the absolute latest status or any subsequent confirmation, revision or withdrawal.

Q: Is it part of a series?

A: Yes — it is part of the ISO 6336 series (calculation of load capacity of spur and helical gears). Other parts address basic principles, pitting (surface durability), tooth‑root bending strength, materials/quality and variable‑load life, plus several technical specifications and TRs for scuffing and micropitting.

Q: What are the key keywords?

A: tooth flank fracture, contact fatigue, case‑carburized gears, Hertzian stress, case hardening depth (CHD), reduced radius of curvature, spur gears, helical gears, ISO 6336, ISO 53.