30204 bearing: complete specifications & equivalents
The 30204 is a ISO 355 radial bearing sized 20 x 47 x 15.25 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Bore diameter d | 20 mm |
| Outer diameter D | 47 mm |
| Width B | 15.25 mm |
| Seal / shield | open |
| Internal clearance | CN available |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Operating temperature | -30 to +120 °C |
| Mass (geometry estimate) | 111 g |
| Standard | ISO 355 |
| Catalog version | iso355-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 30204 are being backfilled — use the inquiry form for certified values.
Dimensions in inches & 30200-series range
| Bore d | 0.787 in |
|---|---|
| Outer diameter D | 1.85 in |
| Width B | 0.6 in |
| ISO bore code | 04 |
| Radial section height (D−d)/2 | 13.5 mm |
| Smallest bore in 30200-series | 20 mm |
| Largest outer diameter in 30200-series | 200 mm |
| Width range across 30200-series | 15.25–41 mm |
| Bore position in 30200-series (smallest first) | 1 of 19 |
| Bore above smallest 30200-series size | 0 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 30204 | ISO 15 | full Dimensions and internal design equivalent — standard interchange. | ISO 15 boundary-dimension envelope; brand-specific OEM equivalents (NSK/FAG/NTN) pending multi-source data. |
Interchange levels: full standard interchange · partial verify parameters · verify manual confirmation required. Links resolve to the equivalent model's specification page where available.
How the 30204 model number is decoded
In the 30200-series the last two digits of 30204 encode the bore: code 04 = 20 mm (code × 5 from 04 upward). The ISO 355 envelope is 47 mm outside diameter and 15.25 mm total assembly width T over the separable cone and cup — 0.787 × 1.85 × 0.6 in, with a 13.5 mm radial section height. Tapered rollers carry combined radial and single-direction axial load; bidirectional thrust needs an opposed pair (X face-to-face or O back-to-back) adjusted at fit-up. With a rotating cone on a 20 mm shaft, typical catalogue practice is a k5 shaft seat with an H7 housing bore, EP lubrication and a defined end-play setting — verify against the load direction and magnitude.
Typical equipment & failure modes
Common applications
- small gearbox shafts
- agricultural implement wheels
- passenger-car wheel hubs
- small trailer axles
- light differential pinions
Known failure patterns
- water and grit pitting in unsealed hubs where the cup-cone joint acts as a debris entry path
- false brinelling from vibration while the axle is stationary during transport
- fretting corrosion on a loose shaft seat when the cone is pressed to an interference that relaxes with wear
- cup creep and housing bore fretting when the outer ring is left without its specified press fit
- roller large-end smearing and scoring against the inner-ring guide rib from loss of the EP lubricant film
Selection pitfalls — read before you substitute
- At 20 mm bore the small 30204 is commonly factory-adjusted in a hub unit; an after-market fit-up must reproduce the specified end play (a typical starting range of 0.02–0.10 mm at the 20 mm shaft) or the wheel runs hot within the first hundred kilometres.
- The 302 light series at 20 mm bore (47×15.25 mm, 13.5 mm section) is the default general-purpose tapered row; a 32204 on the same 20 mm bore uses the same OD but a wider section for heavier load — it is not a like-for-like width swap.
- Before fitting 30204, machine the 20 mm shaft seat and 47 mm housing bore with a relief or small fillet so nothing bridges the bearing chamfer; the 15.25 mm-wide cone and cup only load correctly when the full faces abut, and a large radius pinches the 13.5 mm radial section.
- The 30204 cup drives into the 47 mm housing bore with a sleeve against its outer face only; pressure on the inner ring or cage transfers through the rollers and leaves indentations that become spalls within the 15.25 mm load zone.
- Inspect the removed 30204 cone and cup as a pair: pitting on the 47 mm cup with a clean cone usually means seal failure and water ingress, while rib scoring on the 20 mm cone points to wrong preload or lost EP film — the two faults need different corrections.
- Tapered rollers accept virtually no misalignment; a deflected 20 mm shaft or a tilted housing shoulder concentrates load on one end of the 15.25 mm-wide roller row — align seats and verify housing perpendicularity.
- Press the 30204 cone onto the 20 mm shaft with force on the inner ring and the cup into the 47 mm housing on the outer ring; driving through the rollers or transmitting mounting force across the assembly brinells the raceways.
Frequently asked questions
What are the dimensions of a 30204 tapered roller bearing?
A 30204 single-row metric tapered roller bearing per ISO 355 has a 20 mm bore, 47 mm outer diameter and 15.25 mm total assembly width (0.787 × 1.85 × 0.6 in), a 13.5 mm radial section and roughly 111 g geometry-based estimated mass; catalogue masses vary with roller and cage design.
How does the 30204 bore code work?
The last two digits of 30204 are bore code 04, giving 04 × 5 = 20 mm bore — the same convention as 6xx ball bearings, starting at code 04 (20 mm). The 47 mm OD and 15.25 mm width come from the ISO 355 diameter and width series, not the bore code alone.
What is the cone and cup of 30204?
Tapered roller bearings are separable: the cone is the inner ring with the tapered rollers and cage, the cup is the outer ring. 30204 denotes a matched cone-and-cup set. They are fitted separately — cone pressed on the shaft, cup in the housing — and adjusted against each other.
How is the preload or clearance of 30204 set?
At fit-up the 20 mm-bore cone is tightened against the cup while the hub is rotated, seated, then backed off to the specified end play — a typical starting range of 0.02–0.10 mm for a 20 mm bore — and locked with shims, a locknut or a spacer. Too tight overheats and seizes the rib; too loose causes skid, noise and early wear. Confirm the exact figure in the hub or axle-maker procedure.
Can 30204 take axial load in both directions?
A single 30204 takes thrust in one direction only — the roller large ends bear against the inner-ring rib under load. Bidirectional axial load requires an opposed pair: X (face-to-face) tolerates misalignment slightly better, O (back-to-back) gives a wider load centre and more moment stiffness.
Reviewed & verified by the MPN Base engineering desk against source catalog iso355-geometry on 2026-09-24. Read our editorial & correction policy.