21309CK bearing: complete specifications & equivalents
The 21309CK 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 | 912 g |
| Manufacturer designation | NTN 21309CK |
| 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 |
|---|---|---|---|
| 21309C | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same NTN 21300-series envelope, cage and ratings; this is the tapered-bore execution (K, 1:12) of the cylindrical-bore 21309C — mounting (adapter/withdrawal sleeve or tapered seat, drive-up) differs. 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 21309CK model number is decoded
The NTN order number 21309CK identifies a 45×100×25 mm (1.772 × 3.937 × 0.984 in) spherical roller bearing, 1:12 tapered bore (K), to the ISO 15 boundary plan. Reading the full code: the number gives the 45×100 mm envelope, C/CK names the cage/capacity execution, K marks the 1:12 tapered bore for adapter/withdrawal-sleeve mounting, and plain outer ring (no D1/W33 groove) completes the order number. The plain outer ring (no D1/W33 groove) makes relubrication part of the design: fresh grease reaches the rolling elements through the outer-ring feature rather than relying solely on end-side packing. Grease/oil ratio: the 4,400 r/min limiting value is .77 of the 5,700 r/min oil value; heavy 25 mm-wide cages run hot in churning grease, so quantity and groove supply both matter. Never mount 21309CK by striking the outer ring through the roller set; drive through ring faces (or the adapter sleeve nut) and support the ring square to avoid brinelling the 100 mm race.
Typical equipment & failure modes
Common applications
- industrial gearbox and reducer shafts
- conveyor pulley and elevator drum shafts
- stone crusher and screen eccentric shafts
- papermaking and printing press rolls
Known failure patterns
- lubricant starvation at the centre rib area when the D1/W33 groove is not connected to a relubrication supply
- 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
- hard-particle indentation through the open arrangement in dusty mining duty
- water-induced pitting in washdown or outdoor duty without effective external seals
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 21309CK is greased for life.
- Self-aligning does not mean unlimited misalignment: beyond the catalogue angle the outer ring's spherical travel is exhausted and the 114 kN rating no longer applies.
- 213-series C/CK executions use the C cage/design code — CK adds the 1:12 tapered bore; quote 21309CK in full because a C cannot be mounted on an adapter-sleeve tapered seat.
- K and K30 are different tapers — K is 1:12 and K30 is 1:30 on the wide series; an adapter sleeve for one will not mount the other 45 mm bearing, and drive-up procedures differ.
- K and K30 are different tapers — K is 1:12 and K30 is 1:30 on the wide series; an adapter sleeve for one will not mount the other 45 mm bearing, and drive-up procedures differ.
- The 114/106 kN ratings, 14.1 kN Pu and 912 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for 21309CK (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 21309CK?
21309CK 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 912 g. It is open, with pressed-steel cage of the 213-series C design and a 1:12 tapered bore.
What is the difference between the K/K30 tapered bore and the cylindrical bore versions?
K denotes a 1:12 tapered bore. 21309CK mounts on an adapter sleeve (or tapered shaft seat) and is driven up to the specified residual clearance; its cylindrical-bore counterpart in the same envelope and ratings is 21309C.
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. 21309CK is the C design-code execution.
What do D1 and W33 mean on 21309CK?
21309CK 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 21309CK 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.