- When ordering custom gears, always request a comprehensive material test report (MTR) per EN 10204 3.1 or 3.2, showing chemistry (e.g., C, Mn, Cr, Mo, Ni percentages), tensile strength, yield strength, elongation, reduction of area, and hardness (Brinell or Rockwell). For critical applications (aerospace, defense, medical), require 3.2 certification with independent third-party verification.
- Second, demand heat treatment certificates including time-temperature profiles, case depth (effective and total), core hardness, surface hardness, and tempering details – essential for carburized or induction-hardened gears.
- Third, obtain non-destructive testing (NDT) reports – magnetic particle inspection (MPI) for surface cracks in ferrous gears, liquid penetrant (LPI) for non-ferrous, or ultrasonic (UT) for internal flaws. For high-stress gears, specify 100% MPI on tooth roots and fillets.
- Fourth, dimensional inspection reports – key parameters measured via CMM or gear tester: profile deviation (fα), helix deviation (fβ), pitch deviation (fpt), runout (Fr), and tooth thickness (span measurement or over pins). Request a full gear analytical chart showing AGMA or ISO quality grade.
- Fifth, surface finish reports (Ra, Rz) for flanks and bore – critical for lubrication and noise.
- Sixth, first article inspection (FAI) per AS9102 or PPAP level 3 for automotive – includes all dimensions on drawing, ballooned and measured.
- Seventh, cleanliness certificates if gears are for precision assemblies (e.g., robot joints).
- Finally, ask for traceability – each gear or lot marked with a unique ID linking to all certs. For plastic gears, request moisture content, tensile modulus, and heat deflection temperature.
Without these documents, you risk premature failure – e.g., case depth too shallow leads to pitting; wrong chemistry causes brittle fracture. Reputable custom gear shops provide these in a digital package.
Note: 3.1 MTR costs less than 3.2 but is not accepted for EU pressure equipment or airframe parts. Plan a 5–10% cost increase for full certification.