FAQs
1. What do the bearing clearance designations C0, C2, C3, C4, and C5 mean?
These refer to the bearing’s internal radial clearance grade.
C2: smaller than Normal clearance (tighter)
C0 / CN: Normal clearance (most common)
C3: greater than Normal clearance (often for higher temperature / interference fit / higher speed)
C4, C5: larger than C3 (for even higher temperature or heavier interference / harsher conditions)
Selection tip: Interference fit, higher operating temperature, or higher speed → consider C3/C4; general use → C0/CN.
2. How can bearing accuracy be distinguished (P0, P6, P5, P4, P2)?
Accuracy classes describe control of dimensional tolerances and runout. Higher class = higher precision.
P0 (Normal): most common for general machinery
P6 / P5 (Higher precision): motors, gearboxes, higher-speed applications
P4 / P2 (High / Ultra-high precision): machine tool spindles and precision equipment
Note: Higher precision usually means higher cost and stricter requirements for shafts/housings and installation.
3. How to choose the right bearing?
A reliable selection is based on these 6 key factors:
Load type: radial / axial / combined
Load level: steady vs shock, misalignment, eccentric load
Speed: low / medium / high rpm
Space limits: OD, width, mounting constraints
Environment: dust, moisture, corrosion, temperature
Fit & lubrication: interference fit, grease or oil
If you share speed + load + working condition + shaft/housing size, we can recommend a suitable model quickly.
4. What are bearing loads and load ratings (load capacity)?
Load capacity is commonly expressed by two ratings:
C (Basic dynamic load rating): relates to fatigue life under rotation
C0 (Basic static load rating): relates to resistance to permanent deformation under heavy/static load or shock
Simple rule: continuous rotation → focus on C; low speed/heavy load/shock → focus on C0.
5. What are rolling bearings?
Rolling bearings carry load using rolling elements (balls or rollers) rolling between the inner and outer rings.
Advantages: low friction, high efficiency, low starting torque, standardized sizes.
Common types: deep groove ball, angular contact ball, cylindrical roller, spherical roller, tapered roller, thrust bearings.
6. What are the types of loads on bearings?
There are three common types:
Radial load: perpendicular to the shaft axis
Axial load (thrust): along the shaft axis
Combined load: radial and axial loads at the same time
7. What is radial load in bearings?
A force acting perpendicular to the shaft centerline.
Examples: belt tension, gear mesh force, rotor weight, etc. Many deep groove ball bearings mainly carry radial loads.
8. What is axial load (thrust load) in bearings?
A force acting along the shaft axis.
Examples: thrust from helical gears, axial force from pump impellers, screw drives, etc.
Note: Not every bearing is suitable for heavy thrust loads—angular contact, tapered roller, and thrust bearings are typically better choices.
9. What is the difference between sealed bearings (2RS/RS) and shielded bearings (ZZ/Z)?
The main differences are protection level, friction, and speed capability.
2RS/RS (Rubber seals): better against water and dust, but slightly higher friction and lower limiting speed
ZZ/Z (Metal shields): mainly dust protection, limited water resistance; lower friction and higher speed capability
Selection tip: wet/muddy/dusty conditions → 2RS; high speed/clean environment → ZZ.
10. Why does a bearing become noisy or overheat?
Common causes include:
insufficient lubrication / wrong grease type
misalignment, mounting damage, overly tight fit
incorrect clearance selection (e.g., using C0 under high temperature + interference fit)
contamination (dust, chips, water)
poor shaft/housing accuracy or excessive geometric errors
bearing quality issues or improper storage/handling
Suggestion: check lubrication and mounting first, then review fits, sealing, and operating conditions.
11. What temperature can a bearing withstand?
It depends on steel material/heat treatment and especially the lubricant.
Standard bearings with general-purpose grease: suitable for moderate temperatures
High-temperature conditions: use high-temp grease or special bearing materials/heat treatment
Key point: in many cases, the lubricant limits temperature more than the steel itself.
12. How is bearing service life estimated?
Engineering calculations often use L10 life—the life that 90% of identical bearings will achieve under the same conditions.
Life is strongly influenced by load, speed, lubrication, cleanliness, installation accuracy, and alignment.
For a more accurate estimate: provide load and speed (and operating factors), and we can calculate a closer life value.
13. What are the key precautions for bearing installation?
Three rules: clean, aligned, correct force application.
Clean the shaft/housing and tools; prevent dirt or chips entering the bearing
Apply press force only on the ring with interference fit (avoid transmitting force through rolling elements)
Never strike the bearing directly on functional surfaces; impact can cause dents and early failure
14. Do bearings need regreasing or relubrication?
It depends on whether the bearing is “sealed-for-life” or maintainable:
Sealed/Shielded grease bearings (2RS/ZZ): often factory-greased and maintenance-free or long-interval maintenance
Open bearings / oil systems: require relubrication based on temperature, speed, and contamination
Tip: Over-greasing can also cause overheating—more is not always better.
15. What do bearing suffixes mean (e.g., C3, 2RS, ZZ, NR, TN9)?
Suffixes indicate design/configuration differences. Common ones include:
C3/C4: clearance class
2RS/RS: rubber seals
ZZ/Z: metal shields
NR: snap ring groove (circlip groove)
TN9 / PA66: polyamide (nylon) cage (suffixes vary slightly by brand)
If you send us a full bearing code, we can break down each part for you.
