21310CK bearing: complete specifications & equivalents
The 21310CK is a ISO 15 radial bearing sized 50 x 110 x 27 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 50 mm |
| Outer diameter D | 110 mm |
| Width B | 27 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 131 kN |
| Basic static load rating C0 | 127 kN |
| Fatigue load limit Pu | 13.7 kN |
| Limiting speed (mechanical) | 4000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1190 g |
| Manufacturer designation | NTN 21310CK |
| 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 | 1.969 in |
|---|---|
| Outer diameter D | 4.331 in |
| Width B | 1.063 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 30 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) | 3 of 14 |
| Bore above smallest 21300-series size | 10 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 21310C | 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 21310C — 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 21310CK model number is decoded
For heavy radial load with misalignment on a 50 mm shaft, NTN supplies 21310CK: sphered outer raceway, two roller rows, pressed-steel cage of the 213-series C design, oil speed 5,200 r/min. The leading digits are the ISO 15 dimension series (21300 series); the bore code resolves to 50 mm (two-digit code ×5, with the 00–03 exception table), and 110 mm OD / 27 mm width follow the general plan. 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. The 30.0 mm section height hosts the spherical roller geometry; shaft and housing fillet radii must clear the chamfer table so the 27 mm-wide ring seats fully on both sides. Never mount 21310CK 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 110 mm race.
Typical equipment & failure modes
Common applications
- conveyor pulley and elevator drum shafts
- stone crusher and screen eccentric shafts
- papermaking and printing press rolls
- pump and fan shafts under heavy belt load
Known failure patterns
- lubricant starvation at the centre rib area when the D1/W33 groove is not connected to a relubrication supply
- machined EM cage wear from inadequate oil film at the cage-guiding surfaces
- micro-pitting when the EHL film is thinner than the raceway composite roughness
- rolling-contact fatigue after the catalogue L10 life at the actual load
- water-induced pitting in washdown or outdoor duty without effective external seals
Selection pitfalls — read before you substitute
- Vibrating-duty 50 mm bearings need the right clearance class and secure fits; verify the k5/m5 seat and relubrication routing rather than assuming the open 21310CK is greased for life.
- 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 50 mm bearing, and drive-up procedures differ.
- Minimum load must be maintained even at rest under vibration: an unloaded 21310CK on a stopped screen false-brinells; parking brakes and shaker isolation both matter.
- Minimum load must be maintained even at rest under vibration: an unloaded 21310CK on a stopped screen false-brinells; parking brakes and shaker isolation both matter.
- 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 50 mm bearing, and drive-up procedures differ.
- The 131/127 kN ratings, 13.7 kN Pu and 1190 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for 21310CK (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 21310CK?
21310CK is an NTN double-row spherical roller bearing to ISO 15: 50 mm bore, 110 mm OD and 27 mm width (1.969 × 4.331 × 1.063 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 131 kN, C0 127 kN, Pu 13.7 kN, grease limiting speed 4,000 r/min, oil 5,200 r/min, mass about 1190 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. 21310CK 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 21310C.
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. 21310CK is the C design-code execution.
What do D1 and W33 mean on 21310CK?
21310CK 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 21310CK 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 — 131 kN C / 127 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.