How to Select Slim‑Thin Ball Bearing for Aerospace Applications

Step 1: Determine Bearing Type

Three types are widely used in aerospace:

1. Deep‑groove slim thin ball bearings: For general airborne equipment and precision mechanisms
2. Four‑point contact slim thin ball bearings (X‑type): Can bear radial and bidirectional axial loads simultaneously; the most common choice for aerospace
3. Angular‑contact slim thin ball bearings: For high‑speed spindles and servo mechanisms

Priority recommendation: Four‑point contact slim thin ball bearings for light weight, compact size and high load capacity.

Step 2: Select Precision Grade (Non‑negotiable for aerospace)

1. General airborne equipment: ABEC‑5 / ISO Class 5 (P5)
2. High‑speed instruments, UAVs, inertial navigation systems: ABEC‑7 / ISO Class 4 (P4)
3. High‑end aero‑engines and guidance systems: ABEC‑9 / ISO Class 2 (P2)

Required supporting specifications:

1. Raceway Finish: Surface roughness Ra ≤ 0.1–0.2 μm
2. Race Runout: Strict control of micrometer‑level radial runout

Step 3: Choose Cage Type (Aerospace‑only designs; stamped steel cages are prohibited)

1. Snap‑Over Phenolic Cage: One‑piece rivet‑free design, lightweight, stable for high‑speed light‑load applications
2. Toroid Separator: Integral ring separator for balls, superior shock resistance and stability; standard for four‑point contact bearings

Avoid stamped steel cages and nylon cages due to poor temperature resistance and short service life.

Step 4: Select Sealing Type (Aerospace‑grade only)

• Preferred: 2 PTFE Seals, double‑sided
• Low friction, resistant to −70 °C low temperature, compatible with aerospace fluids, anti‑aging
• Open type: For external oil lubrication
• Not recommended: Standard rubber 2RS seals (poor temperature resistance, prone to failure)

Step 5: Select Lubricant (Strictly matched to working conditions)

1. Maintenance‑free long‑life service, wide temperature range (−73 °C ~ +121 °C):

Mobil Grease 28 (MIL‑G‑81322), standard aerospace grease

2. Ultra‑low‑temperature high‑speed oil lubrication:

Tribolube‑L3 Light Oil (−57 °C)

3. Fire‑resistant high‑temperature airborne applications:

Brayco Micronic 882 Oil (MIL‑PRF‑83282D)

Sealed bearings: Mobil Grease 28 preferred; Open high‑speed bearings: Light Oil preferred. 

Step 6: Material & Special Functions

1. Standard material: High‑purity AISI 52100 aerospace‑grade bearing steel
2. Non‑magnetic equipment (navigation / magnetic sensors): Non‑magnetic stainless steel (440C non‑magnetic grade)
3. Servo / variable‑frequency motors: Add VL0241 outer‑ring insulating coating to prevent electrical corrosion
4. Environmental requirements: Salt spray resistance, compatibility with aerospace hydraulic oil and fuel, moisture resistance

Step 7: Size, Load & Weight Reduction (Core aerospace requirement)

1. Choose the thinnest cross‑section possible under load constraints to minimize weight
2. Four‑point contact design bears both radial and axial loads, reducing the number of bearings for further weight saving
3. Verify DN value, radial/axial load, shock load and operating temperature