Postcodes and Their Meanings for Bearings
Codes for Sealing, Dust Prevention, and External Shape Modifications
Postcodes for rolling bearings are used to indicate aspects such as the internal structure of the bearing, sealing/dust prevention, external shape modifications, changes to cage structures or materials, as well as alterations to bearing component materials, tolerance grades, clearance, and other related details. These are represented by letters or numbers combined with letter symbols. Below, the content related to commonly used bearings, including sealing/dust prevention, external shape modifications, and changes to cage structure or material, is introduced:
| Code | Meaning | Example |
|---|---|---|
| -RS | Bearing with one side skeleton rubber seal (contact type) | 6210-RS |
| -2RS | Bearing with two sides skeleton rubber seals (contact type) | 6210-2RS |
| -RZ | Bearing with one side skeleton rubber seal (non-contact type) | 6210-RZ |
| -2RZ | Bearing with two sides skeleton rubber seals (non-contact type) | 6210-2RZ |
| -Z | Bearing with one side dust cover | 6210-Z |
| -ZZ | Bearing with two sides dust covers | 6210-ZZ |
| -RSZ | One side with contact-type rubber seal, one side with dust cover | 6210-RSZ |
| -RZZ | One side with non-contact-type rubber seal, one side with dust cover | 6210-RZZ |
| N | Outer ring with snap ring groove | 6210N |
| NR | Outer ring with snap ring groove and snap ring | 6210NR |
| -ZN | One side with dust cover, the other side outer ring has a snap ring groove | 6210-ZN |
| -ZNR | One side with dust cover, the other side outer ring has a snap ring groove and snap ring | 6210-ZNR |
| -ZNB | One side with dust cover, the same side outer ring has a snap ring groove | 6210-ZNB |
| U | Thrust ball bearing with aligning seat washer | 53210 U |
| -FS | Bearing with one side felt seal | 6203-FS |
| -2FS | Bearing with two sides felt seals | 6206-2FS |
| -LS | One side with contact-type rubber seal (no groove on the ring) | NU3317-LS |
| -2LS | Two sides with contact-type rubber seals (no groove on the ring) | NNF5012-2LS |
Material Codes for Cages
| Code | Material Name and Description |
|---|---|
| F | Solid cage made of steel, ductile cast iron, or powder metallurgy (additional numbers distinguish materials): |
| F1 | Carbon steel |
| F2 | Graphite steel |
| F3 | Ductile cast iron |
| F4 | Powder metallurgy |
| M | Solid cage made of brass |
| T | Solid cage made of phenolic laminated fabric |
| TH | Cage (basket type) made of glass fiber reinforced phenolic resin |
| TN | Molded cage made of engineering plastic (additional numbers distinguish materials): |
| TN1 | Nylon |
| TN2 | Polysulfone |
| TN3 | Polyimide |
| TN4 | Polycarbonate |
| TN5 | Polyacetal |
| J | Stamped steel cage (additional numbers added to distinguish material changes) |
| Y | Stamped steel cage (additional numbers added to distinguish material changes) |
| V | Full complement rolling elements (no cage) |
Tolerance Grade Codes
Tolerance grade codes are represented by letters or numbers followed by letters. The commonly used grades are 0-grade (ordinary grade), 6-grade, 6X-grade, 5-grade, 4-grade, and 2-grade. Among these:
- 0-grade has the largest tolerance range and is referred to as the ordinary grade, applicable to general-purpose machinery (e.g., ordinary electric motors).
- The tolerance range decreases sequentially with the grade order (0 → 6 → 6X → 5 → 4 → 2), and the precision increases progressively.
Table 3-14 Tolerance Grade Codes and Meanings
| Code | Meaning |
|---|---|
| Default | Tolerance grade conforms to the standard for 0-grade (not marked by default) |
| 6203/P6 | Tolerance grade conforms to the standard for 6-grade |
| 6203/P6/P6X | Tolerance grade conforms to the standard for 6X-grade |
| 30210/P6X/P5 | Tolerance grade conforms to the standard for 5-grade |
| 6203/P5/P4 | Tolerance grade conforms to the standard for 4-grade |
| 6203/P4/P2 | Tolerance grade conforms to the standard for 2-grade |
Note:
The progression of tolerance grades represents increasing precision from 0-grade (ordinary level) to 2-grade (highest precision level).
Clearance Codes
Clearance codes are used to represent the clearance levels of bearings. The following table explains the meanings of different clearance codes and provides correct examples:
| Code | Meaning | Example |
|---|---|---|
| /C1 | Clearance conforms to the standard for 0 group (default, not marked). | 6210 |
| /C2 | Clearance conforms to the standard for 1 group. | NN3006K/C2 |
| /C3 | Clearance conforms to the standard for 2 group. | 6210/C3 |
| /C4 | Clearance conforms to the standard for 3 group. | 6210/C4 |
| /C5 | Clearance conforms to the standard for 4 group. | NN3006K/C5 |
| /C9 | Clearance conforms to the standard for 5 group. | NNU4920K/C9 |
| /CN | Clearance does not conform to current standard regulations. | 6205-2RS/CN |
Note:
Special combinations for 0-group clearance:
- /CNH: 0-group clearance halved, positioned in the upper section.
- /CNM: 0-group clearance halved, positioned in the middle section.
- /CNL: 0-group clearance halved, positioned in the lower section.
- /CNP: The clearance range spans the upper section of 0-group and the lower section of C3-group.
Simplified Representation Rules:
When tolerance grade and clearance code need to be marked simultaneously, they can be combined into "Tolerance Grade Code + Clearance Group Code" (0-group clearance is not marked).
Examples:
- Tolerance grade P6 + Clearance C3 → /P63
- Tolerance grade P5 + Clearance C2 → /P52