NU204 bearing: complete specifications & equivalents
The NU204 is a ISO 15 radial bearing sized 20 x 47 x 14 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | Generic ISO interchange (unbranded) |
| Bore diameter d | 20 mm |
| Outer diameter D | 47 mm |
| Width B | 14 mm |
| Seal / shield | open |
| Internal clearance | CN / C3 / C4 available |
| Tolerance class | P0 |
| Cage | steel |
| Operating temperature | -30 to +120 °C |
| Mass (geometry estimate) | 101 g |
| Standard | ISO 15 |
| Catalog version | iso15-crb-geometry |
| Last verified | 2026-09-24 |
Source: ISO 15 boundary-dimensions standard · extracted 2026-09-24
Standard-interchange bearing: dimensions per ISO 15; CN clearance, P0 tolerance and a stamped-steel cage are catalogue defaults unless the supplier states otherwise, and mass is a geometry-derived estimate. Brand catalogue load ratings and limiting speeds for NU204 are being backfilled — use the inquiry form for certified values.
Dimensions in inches & NU200-series range
| Bore d | 0.787 in |
|---|---|
| Outer diameter D | 1.85 in |
| Width B | 0.551 in |
| ISO bore code | 04 |
| Radial section height (D−d)/2 | 13.5 mm |
| Smallest bore in NU200-series | 20 mm |
| Largest outer diameter in NU200-series | 180 mm |
| Width range across NU200-series | 14–34 mm |
| Bore position in NU200-series (smallest first) | 1 of 17 |
| Bore above smallest NU200-series size | 0 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the NU204 model number is decoded
In the NU200-series (ISO 15 dimension series) the leading NU marks a single-row cylindrical roller: the outer ring has two integral shoulders and the inner ring none, so the inner-ring/roller assembly floats axially both ways and the bearing locates radially only; the last two digits of NU204 are bore code 04 = 20 mm (code × 5 from 04 upward). The ISO 15 envelope is 47 mm outside diameter and 14 mm width — 0.787 × 1.85 × 0.551 in, with a 13.5 mm radial section height. Straight cylindrical rollers give line contact for high radial capacity at low friction, with no self-alignment; catalogue practice for a rotating inner ring is a k5 shaft seat, H7 housing and C3 clearance. NJ adds one inner shoulder (one-direction location), NUP two shoulders (full location); E denotes a reinforced roller complement — verify against the actual load direction.
Typical equipment & failure modes
Common applications
- textile and packaging machinery rolls
- light conveyor drive shafts
- small gearbox layshafts and pinion shafts
- fractional electric motor armatures
- two-wheeler and appliance transmissions
Known failure patterns
- fretting corrosion on an interference inner-ring seat that creeps under a loose fit
- false brinelling indentations at the roller pitch when an idle bearing sits in machine vibration
- inner-ring shoulder damage from cold mounting force transmitted through the roller set
- thermal seizure when an interference fit plus hot running removes all residual C3 clearance
- roller and raceway smearing when a lightly loaded NU row skids at start-up or below the minimum load
Selection pitfalls — read before you substitute
- At 20 mm bore the small NU204 commonly shares a gearbox bore with a 6-series deep-groove row; do not substitute by envelope alone — the cylindrical roller carries far more radial load but no thrust, so any helical-gear axial force needs a paired angular-contact or NJ locating row.
- The NU2 light series at 20 mm bore (47×14 mm) is the default gearbox cylindrical row; on the same bore an NU304 is larger with a much higher rating — do not replace a failed NU304 with an NU204 without re-rating L10 life.
- Before fitting NU204, machine the 20 mm shaft seat and 47 mm housing bore with a relief or undercut so nothing bridges the chamfer; the separable rings only carry load when their full faces abut, and a large fillet pinches the 13.5 mm radial section.
- With a separable NU204, mount the inner-ring/roller assembly on the shaft and the plain outer ring in the housing independently; check that the outer ring is free to float the specified amount after closing the housing — a pinched outer ring turns the floating bearing into an accidental locating one.
- Relubricate NU204 with the shaft turning so fresh grease or oil reaches the full 14 mm roller length; grease forced into a stationary row packs the entry and leaves the far side of the 20 mm bore starved.
- Apply mounting force to the ring with the interference fit — inner ring for a shaft fit, outer ring for a housing fit; pushing the 20 mm inner ring home through the rollers brinells the 47 mm outer raceway.
- Order clearance for the fit: a rotating interference inner ring on a 20 mm shaft plus thermal growth consumes CN play, so C3 is the normal industrial default and C4 serves hot or vibratory mounts; CN suits loose outer-ring floating arrangements in bored housings.
Frequently asked questions
What are the dimensions of an NU204 cylindrical roller bearing?
An NU204 single-row cylindrical roller bearing per ISO 15 has a 20 mm bore, 47 mm outer diameter and 14 mm width (0.787 × 1.85 × 0.551 in), a 13.5 mm radial section and roughly 101 g geometry-based estimated mass; catalogue masses vary with cage and E design.
How does the NU204 bore code work?
The letters give the ring/shoulder design (NU = axially free, NJ = one inner shoulder, NUP = two shoulders) and the last two digits are bore code 04: 04 × 5 = 20 mm. The 47 mm OD and 14 mm width come from the ISO 15 dimension series (NU200), which shares its boundary plan with the 6-series deep-groove envelopes.
What is the difference between NU, NJ, N and NUP designs?
NU (like the NU204) has a shoulderless inner ring and floats axially in both directions; NJ has one integral inner-ring shoulder and locates the shaft in one direction; N has two inner shoulders and a shoulderless outer ring (mirror of NU); NUP adds a second, loose shoulder so the inner ring locates in both directions. Select by the shaft locating scheme, not by load rating — the envelopes are identical.
Can an NU204 take axial load or misalignment?
No thrust in the NU design: any sustained axial force scores the roller ends and ring flanges, so locate the shaft with an NJ/NUP row, a paired angular-contact bearing or a deep-groove row elsewhere. Misalignment is likewise not tolerated — line contact between cylindrical rollers and raceways edges under even small angular errors; use a spherical roller bearing where shaft deflection or housing misalignment is expected.
What does the E suffix mean and which clearance should be ordered?
E (as in NU204E) is the reinforced design: larger/optimised rollers raise the basic load rating over the basic designation in the same 20×47×14 mm envelope. For clearance, C3 is the usual default with an interference fit on a rotating inner ring because fit and thermal growth reduce residual play; use CN mainly for loose floating outer-ring mounts and C4 for hot or vibratory duty.
Reviewed & verified by the MPN Base engineering desk against source catalog iso15-crb-geometry on 2026-09-24. Read our editorial & correction policy.