Bearing Nomenclature: Decoding the Numbers Behind Precision Performance

What Is Bearing Nomenclature?

Bearing designations follow a standardized system, often with 3-5 digits in the basic code, plus prefixes and suffixes. The basic part identifies type, design, and dimensions; extras detail seals, cages, or tolerances. For example, SKF and FAG use similar ISO-based schemes where the first digit/letter shows type (e.g., 6 for deep groove ball bearings), next two indicate width/diameter series, and last two give bore size (multiply by 5 for mm diameter).

This system promotes interchangeability across brands like NSK, NTN, or your go-to suppliers.

Breaking Down the Basic Designation

• Type Code: First digit/letter flags the bearing family—6xxx for single-row deep groove ball, 2xxx for spherical roller, 3xxx for angular contact.

• Dimension Series: Middle two digits—first for width/height (e.g., 0 light, 2 medium), second for diameter (e.g., 0 extra light, 9 extra heavy). Example: 62xx is medium width, light diameter series.

• Bore Diameter: Last two digits x 5 = bore in mm. So, 6205 means 25mm bore (05 x 5). For bores ≥10mm, it's direct; under 10mm, use 00-03 codes (e.g., 618/8 for 8mm).

Take 6305ZZ: 6=deep groove ball, 3=medium series, 05=25mm bore; ZZ=metal shields on both sides.

Prefixes and Suffixes Explained

Prefixes (rare) denote housing or locating features; suffixes add specifics:

Category	Examples	Meaning
Cages	TVP2, MB, M	Glass fiber polyamide window cage; brass cage, roller-guided; one-piece brass.
Seals/Shields	2RSR, ZZ, VSR	Rubber seals both sides (NBR); metal shields; fluoro rubber seals for high temp.
Clearance	C2, C3, C4	Reduced, normal, increased radial clearance (C3 common for heat expansion).
Precision/Taper	P5, K, K30	ISO tolerance class 5; taper bore 1:12 or 1:30.
Special	XL, E1	X-life (enhanced performance); increased capacity design.

FAG spherical roller suffixes like E1-XL-MB mean X-life with brass cages on

inner ring guidance.

Why It Matters for Your Operations

Mastering nomenclature cuts downtime by speeding part identification and matching OEM specs. In bearings manufacturing—like at ABPL Bearings— it aids quality control and custom orders. Always cross-check catalogs for brand variants, as minor differences exist (e.g., Timken vs. SKF)

For hands-on tips, print a nomenclature chart and keep it shop-floor ready. Next time you spec a 6204-2RS1/C3, you'll know it's a 20mm bore deep groove ball with one seal and loose clearance—perfect for pumps or fans.