21309C bearing: complete specifications & equivalents
The 21309C is a ISO 15 radial bearing sized 45 x 100 x 25 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 45 mm |
| Outer diameter D | 100 mm |
| Width B | 25 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 114 kN |
| Basic static load rating C0 | 106 kN |
| Fatigue load limit Pu | 14.1 kN |
| Limiting speed (mechanical) | 4400 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 927 g |
| Manufacturer designation | NTN 21309C |
| Standard | ISO 15 |
| Catalog version | NTN Ball and Roller Bearings CAT.No.2203E |
| Last verified | 2026-10-01 |
Source: catalog reference (NTN Ball and Roller Bearings CAT.No.2203E) · extracted 2026-10-01
Parameters extracted from the official NTN Ball and Roller Bearings catalogue (NTN Ball and Roller Bearings CAT.No.2203E); NTN® is a trademark of NTN Corporation, used here for identification only — mpnbase is not an authorized NTN distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at ntnglobal.com.
Dimensions in inches & 21300-series range
| Bore d | 1.772 in |
|---|---|
| Outer diameter D | 3.937 in |
| Width B | 0.984 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 27.5 mm |
| Smallest bore in 21300-series | 40 mm |
| Largest outer diameter in 21300-series | 240 mm |
| Width range across 21300-series | 23–50 mm |
| Bore position in 21300-series (smallest first) | 2 of 14 |
| Bore above smallest 21300-series size | 5 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 21309CK | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same NTN 21300-series envelope, cage and ratings; this is the cylindrical-bore execution of the tapered-bore 21309CK (K/K30 sleeve or tapered-seat mounting). Verify shaft arrangement. |
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 21309C model number is decoded
21309C is the C design-code execution of NTN's spherical roller range for a 45 mm shaft — 114 kN basic dynamic capacity in a 927 g, open ISO 15 envelope. Numbering ties 21309C to its envelope and execution: same-number EA versus EM or plain variants share the 45 mm bore but differ in cage and sometimes mass, so they are quoted as separate articles. The sphered outer raceway lets the inner-ring assembly pivot, accommodating shaft deflection and housing misalignment (around 1–2° for this class; use the 2203E value for the exact series) without edge loading the rollers. Catalogue mass 927 g (0.93 kg) for the 45×100×25 mm execution includes the C design-code cage and both roller rows; shaft and housing shoulders must support that ring squarely. Fillet radii on shaft and housing must clear the ring chamfers of the 25 mm-wide set; use the NTN shoulder/withdrawal-groove table rather than copying a ball-bearing layout.
Typical equipment & failure modes
Common applications
- vibrating screen and feeder shafts
- industrial gearbox and reducer shafts
- conveyor pulley and elevator drum shafts
- stone crusher and screen eccentric shafts
Known failure patterns
- raceway spalling at the roller ends when misalignment or deflection concentrates the line contact
- cage damage when a mounting force is applied through the roller set instead of the ring face
- sliding wear and heat when relubrication intervals ignore the groove (D1/W33) supply path
- false brinelling on stopped machines exposed to screen or crusher vibration
- rolling-contact fatigue after the catalogue L10 life at the actual load
Selection pitfalls — read before you substitute
- Vibrating-duty 45 mm bearings need the right clearance class and secure fits; verify the k5/m5 seat and relubrication routing rather than assuming the open 21309C is greased for life.
- Minimum load must be maintained even at rest under vibration: an unloaded 21309C on a stopped screen false-brinells; parking brakes and shaker isolation both matter.
- 213-series C/CK executions use the C cage/design code — CK adds the 1:12 tapered bore; quote 21309C in full because a C cannot be mounted on an adapter-sleeve tapered seat.
- The D1/W33 groove only helps if the housing has a matching grease passage; mounting a grooved 21309C in a solid block with no port wastes the feature and leaves the centre rows under-lubricated.
- Minimum load must be maintained even at rest under vibration: an unloaded 21309C on a stopped screen false-brinells; parking brakes and shaker isolation both matter.
- The 114/106 kN ratings, 14.1 kN Pu and 927 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for 21309C (C design-code); another maker's same-envelope part revises internal geometry, so re-verify ratings and cage before substitution on vibrating or rated drives.
Frequently asked questions
What are the dimensions and catalogue data of 21309C?
21309C is an NTN double-row spherical roller bearing to ISO 15: 45 mm bore, 100 mm OD and 25 mm width (1.772 × 3.937 × 0.984 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 114 kN, C0 106 kN, Pu 14.1 kN, grease limiting speed 4,400 r/min, oil 5,700 r/min, mass about 927 g. It is open, with pressed-steel cage of the 213-series C design.
What is the difference between the K/K30 tapered bore and the cylindrical bore versions?
21309C has a cylindrical bore and mounts directly on a machined shaft seat. Its tapered-bore counterpart is 21309CK (K = 1:12, or K30 = 1:30 on the wide series), intended for adapter/withdrawal-sleeve mounting.
What do EA and EM mean on NTN spherical roller bearings?
EA is the NTN standard-capacity/high-capacity execution with a pressed sheet-steel window cage; EM is the high-capacity execution with a one-piece machined brass cage. Both use the optimised symmetric-roller design, but cage identity changes mass, speed behaviour and suitability for duties like vibrating screens, so they are separate order numbers. 21309C is the C design-code execution.
What do D1 and W33 mean on 21309C?
21309C is listed without a D1/W33 outer-ring groove in 2203E; lubrication is supplied from the ring sides. D1 (NTN spelling) and W33 add the annular groove plus holes and are ordered as distinct suffixed executions of the same envelope.
How much misalignment and axial load can 21309C take?
The sphered outer raceway compensates static and dynamic misalignment in the order of 1–2° (verify the exact 2203E figure for the 21300 series); beyond that, load concentrates on one roller row. Load is predominantly radial with a moderate axial share in either direction — 114 kN C / 106 kN C0 — but sustained pure axial load is not recommended because it unloads one row.
Reviewed & verified by the MPN Base engineering desk against source catalog NTN Ball and Roller Bearings CAT.No.2203E on 2026-10-01. Read our editorial & correction policy.