ISO 14635-1:2023

Overview

ISO 14635-1:2023 specifies the FZG test method A/8,3/90 for evaluating the relative scuffing load‑carrying capacity of lubricating oils. Using an FZG four‑square test machine, this standard defines a repeatable procedure to assess lubricant breakdown under high surface pressures, high sliding velocities and controlled temperatures that can cause gear-surface scuffing. The method is technically equivalent to ASTM D5182-19 and CEC L-07-A-95.

Key topics and requirements

• Test machine & setup: FZG four‑square (spur‑gear) rig, dip‑lubrication mode, heating device and revolution counter.
• Test condition A/8,3/90: Type A gear geometry; circumferential velocity at pitch line v = 8.3 m/s; initial oil temperature 90 °C (from load stage 5 onward).
• Test gears: Type “A” gears (module 4.5, pinion z = 16, wheel z = 24, effective tooth width = 20 mm), case‑hardened steel with specified composition, case depth 0.6–0.9 mm, surface hardness 60–62 HRC, accuracy grade Q5 (ISO 1328-1:1995).
• Load procedure: Stepwise increased load stages (see Table 3 in the standard); inspections of pinion tooth flanks after load stage 4 and after each subsequent stage.
• Failure criterion: Failure load stage is reached when the summed scuffing width on the 16 pinion teeth exceeds one gear‑tooth width (20 mm).
• Test materials & cleaning: Use petroleum spirit conforming to ASTM D235 for cleaning.
• Precision: Evaluated per ISO 5725-2. Repeatability r = 1 load stage; reproducibility R = 2 load stages (for failure stages 5–12).
• Safety: Warnings about rotating, loaded shafts and noise - operators must follow local safety regulations.

Applications and users

ISO 14635-1:2023 is intended for:

• Lubricant manufacturers validating anti‑scuffing and extreme‑pressure properties of oils.
• Tribologists and test laboratories performing standardized gear lubrication tests.
• Gear designers and OEMs (industrial, marine, and heavy machinery) who need lubricant characteristic values for gear load‑carrying capacity calculations.
• Quality and compliance teams comparing oil performance across standardized test methods (equivalent to ASTM/CEC methods).

Practical uses include oil product development, specification of lubricants for gearboxes, comparative benchmarking, and supporting gear life and reliability assessments.

Related standards

• ISO 14635 series (other parts for specific gear damage modes)
• ISO 1328-1 (gear accuracy)
• ISO 21920-2 (surface texture)
• ISO 18265 (hardness conversion)
• ASTM D5182-19; CEC L-07-A-95 (equivalent scuffing tests)
• ASTM D235 (cleaning fluid)

Keywords: ISO 14635-1, FZG test, A/8,3/90, scuffing, load-carrying capacity, lubricating oils, four-square test, gear scuffing, ASTM D5182.