Specify the duty, not just the diameter.

1. Application and function

What rotates or translates? What failure would stop the machine? Name the motor, joint, wheel, spindle, roller, gearbox, or guide—not only the bearing.

2. Bearing family

Deep-groove, angular-contact, thin-section, crossed-roller, needle, spherical, tapered-roller, thrust, linear, or open to engineering recommendation.

3. Envelope and interfaces

Bore, outside diameter, width, shoulders, fillets, retention, shaft tolerance, housing tolerance, material, surface finish, and room for installation tooling.

4. Radial, axial, and moment loads

Provide steady, peak, reversing, shock, and combined loads. When exact values are unavailable, provide credible upper bounds and explain the load case.

5. Speed and motion profile

Continuous and peak RPM, oscillation angle, reversals, dwell, acceleration, start-stop frequency, and total operating hours per cycle.

6. Life and reliability target

Required operating hours, cycles, probability of survival, allowable maintenance, and consequences of failure. Catalog dynamic life is not the entire system-life calculation.

7. Precision and stiffness

Runout, repeatability, radial and axial play, preload, angular stiffness, deflection, torque, vibration, and noise targets.

8. Material

Stainless grade, chrome bearing steel, ceramic rolling elements, coatings, cage material, magnetic constraints, galvanic compatibility, and corrosion expectation.

9. Seals, shields, and contamination

Open, non-contact shield, low-torque seal, contact seal, external labyrinth, purge, washdown, dust, fibers, chips, or cleanroom particle requirements.

10. Lubrication

Grease or oil, base oil, thickener, fill, compatibility, food-grade or vacuum constraints, relubrication access, temperature, drag, outgassing, and shelf life.

11. Electrical conditions

For inverter-driven motors, define shaft voltage or current risk and whether insulation, grounding, ceramic rolling elements, or another mitigation is required.

12. Environment

Operating and storage temperature, pressure or vacuum, humidity, salt, cleaning chemistry, radiation, shock, vibration, and ingress requirements.

13. Quantity and ramp

Prototype quantity, validation builds, annual volume, target launch, production location, packaging, traceability, inspection, and second-source strategy.

14. Evidence

Current part number, drawing, CAD section, failure photos, vibration or noise data, lubricant history, test plan, rejected samples, and supplier deviations.