Bearing selection and maintenance notes
Start with the part number, dimensions and operating conditions.
Selection and identification
A part number is only the starting point. Fit, speed, load, temperature and mounting conditions also matter.
01What information should an inquiry include?
Send the brand and complete part number, plus clear photos of the product, nameplate or packaging. If the number is incomplete, include bore, outside diameter, width and mounting position.
- Quantity and required date
- Machine and mounting position
- Speed, temperature, load and environment
02What do C3 and C4 mean?
C3 and C4 identify internal-clearance groups, not accuracy grades. Suitability depends on fits, operating temperature and speed. Retain all clearance, seal and cage suffixes when replacing a bearing.
03How do 2RS, 2Z, RS and ZZ differ?
RS generally identifies a seal on one side and 2RS seals on both sides. Z generally identifies one shield and 2Z or ZZ shields on both sides. Suffix rules vary by manufacturer, so confirm them against the relevant catalog.
04Why can a tapered roller bearing require two numbers?
Some tapered roller bearings use separate numbers for the cone assembly and cup. Send both numbers and confirm whether the bearing is metric or inch series, its mounting direction and whether it is used as a pair.
Mounting and lubrication
Cleanliness, the path of mounting force and the grease quantity are frequent sources of early trouble.
05What should be checked before mounting?
- Check shaft, housing, fillets and fitting surfaces
- Keep tools and the work area clean
- Confirm part number, clearance, seals and direction
- Do not transmit mounting force through the rolling elements
06Is more grease always better?
No. Excess grease can increase churning and temperature; too little may not maintain a lubricant film. The correct quantity depends on bearing space, speed, relubrication method and housing design. Record grease type, quantity and interval.
07Can a bearing be heated with an open flame?
It should not be. Local flame heating can cause uneven temperature, material changes and contamination. Use controlled induction heating and follow the manufacturer's temperature limits.
08How should unused bearings be stored?
Keep the original packaging in a clean, dry place with limited temperature variation. Avoid corrosive chemicals. For long-term storage of large bearings, inspect corrosion protection as recommended by the manufacturer.
Abnormal operation and failure
Record the symptoms before removal. Photos and trend data are more useful than a simple statement that the bearing failed.
09What commonly causes bearing overheating?
Check for excessive or unsuitable grease, tight fits, insufficient clearance, shaft misalignment, seal friction and operating conditions beyond the original design. Record temperature rise, speed and recent maintenance work.
10What should be checked when noise appears?
Determine whether the noise changes with speed, load or temperature, then inspect lubrication, fastening, alignment and surrounding components. Do not diagnose bearing damage from sound alone.
11What are signs of electrical erosion?
Raceways may show fine fluting or pitting, and grease may discolor. With variable-frequency drives, investigate grounding and shaft voltage. The remedy may involve insulated bearings, grounding rings or system-level electrical changes.
12What should be retained after a failure?
- Do not clean or polish the failed surfaces
- Photograph the mounting position, fits and lubricant
- Record operating time, load, speed, temperature and maintenance history
- Retain rings, rolling elements, cage and seals
Technical references: NSK catalogs and maintenance documents · Schaeffler medias. Confirm product-specific limits against the latest manufacturer documentation.
An incomplete part number is still a useful start.
Send clear photos, dimensions and the machine position.