Introduction
Rolling bearings carry designations that encode bore size, type, dimension series and variant options. Reading these codes helps engineers and buyers describe what is installed or required — before requesting a quotation.
This guide explains designation structure at methodology level. Brand-specific suffix systems and cross-reference to other manufacturers require manufacturer evidence — identification support is not an interchange or replacement guarantee.
Three levels of identification
| Level | What you establish | Confidence |
|---|---|---|
| 1. Bearing type | Ball, roller, thrust, mounted unit, linear | High from visual inspection |
| 2. Size series | Bore, dimension series, basic type code | Medium from markings or measurement |
| 3. Variant specification | Clearance, seal, cage, precision suffixes | Requires complete designation or manufacturer data |
Level 1–2 is often enough to route toward the correct type authority. Level 3 is required for exact catalogue replacement.
ISO designation structure
Many rolling bearings follow an ISO-style alphanumeric designation:
| Position | Typical meaning | Example context |
|---|---|---|
| Prefix | Special features or split bearings | Optional; manufacturer-specific |
| Basic number | Bearing type and dimension series | Deep groove ball, cylindrical roller, etc. |
| Bore code | Last digits encode bore diameter | 00–03 special codes; 04+ often bore = code x 5 mm |
| Suffix | Clearance, seal, cage, precision | C3, 2RS, NR, etc. |
Bore diameter codes (common rule)
For many metric designations where bore code is 04 or greater:
- Bore diameter (mm) = bore code x 5
- Example: designation ending in 08 often indicates 40 mm bore (8 x 5)
Codes 00, 01, 02 and 03 follow a special table (10, 12, 15, 17 mm respectively in standard series). Confirm against manufacturer data for non-standard series.
This guide does not replace a complete manufacturer designation table.
Suffix and variant codes
Suffix letters and numbers describe variants. Common examples (verify per manufacturer):
| Suffix | Typical meaning |
|---|---|
| C2, CN, C3, C4, C5 | Internal clearance group |
| ZZ, 2Z | Metal shields on both sides |
| RS, 2RS | Contact seals on one or both sides |
| NR | Snap ring groove in outer ring |
| M, MA | Brass cage variants |
| TN, TV | Polyamide or other cage types |
Suffix meaning can differ between manufacturers. A suffix on one brand does not automatically mean the same on another. Do not infer equivalence from suffix similarity alone.
Markings on the bearing
Inspect the bearing for:
| Marking | Value |
|---|---|
| Manufacturer name or logo | Identifies brand — does not establish equivalence with another brand |
| Complete designation | Primary identification input |
| Country of manufacture | Traceability |
| Bore / OD / width (if stamped) | Verification against designation |
Photograph markings before cleaning or removal. Worn stampings may require dimensional measurement (bore, outside diameter, width) and application context for engineering review.
Data to collect
Before sending an identification or RFQ request, collect:
- Complete designation — from marking, drawing or purchase record.
- Manufacturer name — from bearing face or housing label.
- Dimensions — bore, outside diameter, overall width (if accessible).
- Construction — ball vs roller, single vs double row, sealed vs open.
- Housing type — if mounted unit (pillow block, flange, take-up).
- Application — machine type, load, speed, environment.
- Photos — markings, housing, installation context.
Identification establishes what is installed. Compatibility with another brand or part number is a separate engineering determination requiring governed evidence.
Identification checklist
- Record all visible markings and photograph the bearing.
- Measure bore, OD and width if safe to do so.
- Note bearing type (ball, roller, thrust, mounted).
- Note sealing (open, shielded, sealed).
- Identify manufacturer from logo or documentation.
- Document application and operating conditions.
- Do not assume cross-brand equivalence from visual similarity.
- Send collected data through engineering enquiry.
Next steps
- For selection after identification, read the Industrial Bearing Selection Guide.
- Route to the relevant type authority — for example deep groove ball or spherical roller.
- For mounted units, see Pillow Block and Mounted Bearing Selection.
- For load rating context on the identified type, see Bearing Load Ratings Explained.
Scope and limitations
- This article explains general ISO-style designation structure; manufacturer catalogues own complete suffix tables.
- Identification support does not guarantee interchange, replacement equivalence or cross-brand compatibility.
- Visual similarity does not establish that one bearing substitutes for another.
- Golden Bearing Company confirms compatibility only with governed engineering evidence.