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Designation system

The designations of SKF super-precision bearings follow a system that consists of a basic designation with or without one or more prefixes and/or suffixes.

Examples and the applicable options for cylindrical roller bearings are given below.

Basic bearing designation system


Single row bearing
N 1016 KPHA/HC5SPwhereN 1016 =
K =
HC5 =
SP =

Double row bearings
NN 3020 KTN9/SPVR521whereNN 3020 =
K =
TN9 =
SP =
VR521 =
NNU 49/500 B/SPC3W33XwhereNNU 49/500 =
B =
SP =
C3 =
W33X =

Test Designation 1
Prefixes (n.a.)

Test Designation 2
Basic designation
Bearing design
NSingle row cylindrical roller bearing
NNDouble row cylindrical roller bearing
NNUDouble row cylindrical roller bearing
Dimension series
10In accordance with ISO dimension series 10
30In accordance with ISO dimension series 30
49In accordance with ISO dimension series 49
Bearing size
(x5) 25 mm bore diameter

(x5) 460 mm bore diameter

Bore diameter uncoded [mm]

Catalogue image - Test Designation 3
Suffixes - Internal design and bore shape
Cylindrical bore (no designation suffix)
BModified internal design
Tapered bore, taper 1:12

Test Designation 4
Suffixes - External design (seals, snap ring groove etc.) (n.a.)

Catalogue image - Test Designation 5
Suffixes - Cage design

Machined brass cage, roller centred (no designation suffix)
PHACarbon fibre reinforced PEEK cage, outer ring centred
PA66 cage, roller centred
Glass fibre reinforced PA66 cage, roller centred
TNHAGlass fibre reinforced PEEK cage, outer ring centred

Catalogue image - Test Designation 6.1
Suffixes - Materials, heat treatment
Carbon chromium steel (no designation suffix)
HC5Rollers made of bearing grade silicon nitride Si3N4 (hybrid bearing)

Test Designation 6.2
Suffixes - Accuracy, clearance, preload, quiet running
SPDimensional accuracy in accordance with ISO tolerance class 5, running accuracy in accordance with ISO tolerance class 4
UPDimensional accuracy in accordance with ISO tolerance class 4, running accuracy better than ISO tolerance class 4
Internal clearance
Standard radial internal clearance C1 (no designation suffix)
C2Radial internal clearance greater than C1
CNNormal radial internal clearance
C3Radial internal clearance greater than Normal

Catalogue image - Test Designation 6.3
Suffixes - Bearing sets, matched bearings (n.a.)

Test Designation 6.4
Suffixes - Stabilization (n.a.)

Suffixes - Lubrication
W33Annular groove and three lubrication holes in the outer ring
W33XAnnular groove and six lubrication holes in the outer ring

Test Designation 6.6
Suffixes - Other variants
VR521Bearing supplied with measuring report (standard for NN 30 series bearings with d > 130 mm)
VU001Inner ring raceway with finish-grinding allowance
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