What is ISO 6336‑1 - Calculation of load capacity of spur and helical gears about?  
The formulae in the ISO 6336 series are intended to establish a uniformly acceptable method for calculating the load capacity of cylindrical gears with straight or helical involute teeth.
ISO 6336‑1 is the first part of the multi-series that is applicable to the calculation of load capacity of spur and helical gears. The main objective of ISO 6336‑1 is to minimize gear fatigue failure and prolong service-life of spur and helical gears.
ISO 6336‑1 presents the basic principles of, an introduction to, and the general influence factors for the calculation of the load capacity of spur and helical gears. Together with the other documents in the ISO 6336 series, it provides a method by which different gear designs can be compared. The ISO 6336 series includes procedures based on testing and theoretical studies as referenced by each method. The methods are validated for:
- Normal working pressure angle from 15° to 25°
- Reference helix angle up to 30°
- Transverse contact ratio from 1,0 to 2,5
Note: ISO 6336‑1 is not intended to assure the performance of assembled drive gear systems.
Note: ISO 6336‑1 is not intended for use by the general engineering public.
Note: The formulae in the ISO 6336 series are not applicable when any of the following conditions exist:
- Gears with transverse contact ratios less than 1,0
- Interference between tooth tips and root fillets
- Teeth are pointed
- Backlash is zero
Note: The rating formulae in the ISO 6336 series are not applicable to other types of gear tooth deterioration such as plastic deformation, case crushing, and wear, and are not applicable under vibratory conditions where there can be an unpredictable profile breakdown. The ISO 6336 series does not apply to teeth finished by forging or sintering. It is not applicable to gears that have a poor contact pattern.
Who is ISO 6336‑1 - Calculation of load capacity of spur and helical gears for? 
 ISO 6336‑1 on the calculation of load capacity of spur and helical gears is relevant to: 
- Manufacturers and designers of spur and helical gears
- Product design engineers
- Machinery designers
- Mechanical engineers
- Industries/applications such as automotive, marine, railway, steel, and power plants
Why should you use ISO 6336‑1 - Calculation of load capacity of spur and helical gears?  
Helical gears are becoming more popular as power transmission gears, not only because they can bear bigger loads, but also because their noise and vibration levels are lower in operation than spur gears.
ISO 6336‑1 provides guidance on the safety factor relative to each damage type — pitting, tooth root breakage, tooth flank fracture, scuffing, micro pitting, etc. The risk of failure reduces with the increase of the safety factor and vice versa. You can thus choose the minimum safety factors after careful consideration of critical influences, as recommended in ISO 6336‑1. 
As a result, ISO 6336-1 aids in the accurate and precise calculations of load capacity that can help you manufacture spur and helical gears as per the need of the end-application to meet its load bearing capacity requirements for optimal operational efficiency. This is ultimately help avoid gear fatigue failure and disruptions to the overall system.
What’s changed since the last update?
BS ISO 6336‑1:2019 supersedes BS ISO 6336‑1:2006, which is withdrawn. BS ISO 6336‑1:2019 includes some technical changes with respect to BS ISO 6336‑1:2006. These include: 
- Incorporation of ISO/TS 6336-4, ISO/TS 6336-20, ISO/TS 6336-21, and ISO/TS 6336-22 into Clause 4 (failure mode)
- Update of application factors in Clause 5
- Integration of Clause 10 "Parameters of Hertzian contact"
- Integration of Clause 11 "Lubricant parameters at given temperature"
