NSK NU2304M dimensions and technical reference
NSK NU2304M is a single-row NU-type cylindrical roller bearing with boundary dimensions 20×52×21 mm (bore d × outside diameter D × width B). This reference uses the catalogue row for NU2304, the explicit NU availability column and its standard cage. It is not a generic specification for every bearing with the same bore or base number.
Full designation and cage
The catalogue stem is NU2304. The standard cage code M completes the designation NU2304M; it identifies a machined brass cage.
Axial location and rib arrangement
The NU arrangement permits axial displacement between the rings and is used at a non-locating position. It does not by itself locate the shaft axially.
Load ratings and operating speed
Basic dynamic radial rating Cr is 40.5 kN and basic static radial rating C0r is 30 kN. These are reference ratings for calculation, not allowable machine loads. Both the load ratings and speed values on this page apply to the standard cage; a listed optional cage does not inherit these values without confirmation.
The grease limiting speed is 11000 r/min; the oil-bath limiting speed is 14000 r/min. The thermal oil-bath rating and forced-oil mechanical limit are separate operating references. A dash in the source means not stated, not zero. Load, heat removal, lubricant and duty determine whether a catalogue speed is suitable.
Mounting and selection limits
- Read shoulder diameters and fillet radii with the matching NU/NJ/NUP or N/NF mounting arrangement. The db maximum refers to an adjusting ring for NU and NJ, not a universal shaft shoulder.
- NSK requires increasing da and reducing Da from the tabulated values when axial loads apply. The table does not specify the amount for your assembly, so these figures do not approve an axially loaded installation.
- Mass is printed once for a shared catalogue row. It is retained as a reference, not claimed as an individually verified mass for each rib arrangement.
- ISO Normal follows the omitted precision-suffix rule. The clearance omission rule depends on whether the design is interchangeable; this page does not assert a numerical CN, C3 or CC clearance range.
- Very light loads can cause roller slip and smearing. Shock, vibration, lubrication and alignment must be considered; size matching alone does not establish a substitute.
- An NJ bearing plus a suitable HJ thrust collar is an NH arrangement. No collar designation or complete NH assembly is established by this row. Double-row NN/NNU products and other cage or clearance variants are not covered.
- No machine fitment, CAD model, seal performance or installed preload is established here. Confirm the complete marking and application before using the data.
Technical basis:NSK Rolling Bearings for Industrial Machinery, E1103d (2025), Part C, C132–C133; construction, designation rules and operating cautions C126–C129. Source checked 2026-10-01. Independently organised technical reference, not a sales offer or interchange approval.
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Product specifications
Metric and imperial values are paired where the manufacturer provides both. Expand a section to review its parameters.
Core specifications7 parameters
| Parameter | Symbol | Value |
|---|---|---|
| Variant / construction | Cylindrical roller bearing | |
| Bore diameter | d | 20 mm |
| Outside diameter | D | 52 mm |
| Width | B | 21 mm |
| Basic dynamic load rating | C | 40.5 kN |
| Basic static load rating | C0 | 30 kN |
| Cage | Machined brass |
Boundary dimensions6 parameters
| Parameter | Symbol | Value |
|---|---|---|
| Bore diameter | d | 20 mm |
| Outside diameter | D | 52 mm |
| Bearing width | B | 21 mm |
| Minimum bearing chamfer | r min. | 1.1 mm |
| Minimum secondary bearing chamfer | r1 min. | 0.6 mm |
| Roller inscribed circle diameter | Fw | 28.5 mm |
Catalogue reference mass1 parameter
| Parameter | Symbol | Value |
|---|---|---|
| Approximate shared-row mass — not separately stated for each rib arrangement | 0.217 kg |
Construction8 parameters
| Parameter | Symbol | Value |
|---|---|---|
| Single-row construction type | NU | |
| Rib arrangement | Two outer-ring ribs; ribless inner ring | |
| Standard cage material | Machined brass | |
| Standard cage marking | M | |
| Other cage codes listed for this catalogue row | None listed in this row | |
| Precision — designation omission rule | ISO Normal when no precision suffix is specified | |
| Clearance identification — verify interchangeability | No clearance suffix shown. CN omission applies to interchangeable designs; do not infer a numerical clearance. | |
| Optimized crowning note | No optimized-crowning asterisk on this row |
Load ratings — standard cage2 parameters
| Parameter | Symbol | Value |
|---|---|---|
| Basic dynamic radial load rating | Cr | 40500 N |
| Basic static radial load rating | C0r | 30000 N |
Lubrication-qualified speed — standard cage4 parameters
| Parameter | Symbol | Value |
|---|---|---|
| Thermal speed rating — oil bath | 14000 r/min | |
| Mechanical limiting speed — forced oil circulation | Not stated in this catalogue row | |
| Limiting speed — grease | 11000 r/min | |
| Limiting speed — oil bath | 14000 r/min |
Mounting dimensions — shown arrangement5 parameters
| Parameter | Symbol | Value |
|---|---|---|
| Minimum shaft shoulder diameter | db min. | 24 mm |
| Maximum housing shoulder diameter | Da max. | 45.5 mm |
| Maximum adjusting-ring diameter (NU/NJ arrangement) | db max. | 27 mm |
| Maximum adjacent fillet radius | ra max. | 1 mm |
| Maximum secondary adjacent fillet radius | rb max. | 0.6 mm |