W 638/2.5-2Z Deep Groove Ball Bearing (2.5x6x2.6mm)

How to read this designation →

d — BoreD — Outside DiameterB — Width

Bearing dimensions and basic technical information.

Schematic of a shielded (2Z) single-row deep groove ball bearing with pressed steel shields

Schematic only — for the actual construction, refer to each manufacturer's information.

Bore diameter (d)2.5 mm

Outer diameter (D)6 mm

Width (B)2.6 mm

TypeDeep Groove Ball Bearing

RowSingle Row

ClearanceCN

Cage

Material Stainless steel

Cage materials — Deep Groove Ball Bearing

Suffix	Material	Printed by
`(none)`	Pressed steel	NSK, NTN, Timken
`M / MA / MB`	Machined brass	SKF, Schaeffler (FAG), Timken
`TN9 / TVP / TVH`	Polyamide (glass-fibre reinforced PA66)	SKF, Schaeffler (FAG)
`PH`	PEEK	SKF

Suffix letters are set by each manufacturer; the third column names the brands that print the row. Always confirm the exact variant in the manufacturer's table.

Clearance groups

Group	Meaning
`C2`	Radial internal clearance smaller than normal
`CN`	Normal clearance — the ISO default group, usually not printed in the designation (SKF/FAG may write it as CN or C0)
`C3`	Radial internal clearance greater than normal
`C4`	Greater than C3

CN is the ISO normal clearance group and is usually not printed in the designation; other groups include C2, C3 and C4. The numeric ranges are defined per bearing type and size (ISO 5753), so always compare them in the manufacturer's table.

Bearing materials

Material	Where it appears
Bearing steel	Rings and rolling elements — the standard for every model without a special material note
Stainless steel	Corrosion-resistant versions, e.g. the SKF "W" series
Ceramic rolling elements (hybrid)	Ceramic balls or rollers running in steel rings; electrically insulating and tolerant of poor lubrication
Ceramic-coated steel rings	SKF INSOCOAT: VL0241 coats the outer ring, VL2071 the inner ring (electrical insulation against stray currents)

The material refers to the rings and the rolling elements. Unless a special material is stated, both are bearing steel.

Suffix Information

Suffix Code2Z

CategoryShield

MeaningMetal shields on both sides

DescriptionSheet-metal shields on both sides. The shield is fixed to the outer ring and does not touch the inner ring, so friction and heat stay close to an open bearing; it retains the grease and keeps coarse dirt out, but it does not seal against fine particles or moisture.

Manufacturer Ratings

Load-rating symbols are printed as each manufacturer writes them in its own catalogue, so the same quantity can carry a different symbol from brand to brand.

Brand	Dynamic Load Rating	Static Load Rating	Fatigue Load Limit
SKF W 638/2.5-2Z	C0.117 kN	C00.036 kN	Pu0.002 kN

Speed Ratings

Speed limits depend on sealing and lubrication, and definitions differ by manufacturer. The figures below are for this shielded version (W 638/2.5-2Z). Non-contact seals and shields run close to the open bearing. Always confirm the exact variant in the manufacturer's table.

Brand	Grease shielded (2Z)	Oil shielded (2Z)	Reference	Limiting
SKF W 638/2.5-2Z	—	—	170,000 r/min	85,000 r/min

References

SKF — SKF Group, Rolling Bearings, PUB BU/P1 17000/1 EN, Oct. 2018.

Related Guides

Disclaimer: Data on this page is compiled from publicly available online sources for reference only, and not every model appears in a manufacturer's published catalog. Values may differ between sources and editions — always verify against the manufacturer's current documentation before design or purchase.Full disclaimer →