21310-EK bearing: complete specifications & equivalents
The 21310-EK 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 | SKF |
| 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 | 159 kN |
| Basic static load rating C0 | 166 kN |
| Fatigue load limit Pu | 18.6 kN |
| Reference speed (thermal) | 5600 rpm |
| Limiting speed (mechanical) | 7500 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1600 g |
| Manufacturer designation | SKF 21310 EK |
| Standard | ISO 15 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 9.2 adapter-sleeve executions |
| Last verified | 2026-09-26 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 9.2 adapter-sleeve executions) · extracted 2026-09-26
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 9.2 adapter-sleeve executions); SKF® and SKF Explorer® are trademarks of AB SKF, used here for identification only — mpnbase is not an authorized SKF distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at skf.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 | 10 |
| 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 |
|---|---|---|---|
| 21310 | SKF | full Dimensions and internal design equivalent — standard interchange. | Tapered-bore (1:12) sleeve-mounted execution of 21310; identical ISO 15 envelope, fits H310 adapter sleeve on a 45 mm shaft. |
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 21310-EK model number is decoded
For sleeve mounting on a 50 mm shaft, SKF order number SKF 21310 EK is the 1:12 tapered-bore spherical roller bearing in the 21300-series family (dimension series 13 (heavy OD, normal width)); the cylindrical-bore equivalent is a separate order number, 21310. Numbering ties the bearing to its envelope: 21310-ek means spherical-roller type, dimension series 13, 50 mm bore — which is why the 110×27 mm outline swaps dimensionally with other ISO 15 bearings of the same code. The K in the designation marks the 1:12 tapered bore: SKF mounts it on an H-series adapter sleeve (with KM locknut and MB lock washer) on a plain commercial-grade shaft, or on an AH withdrawal sleeve where the bearing must abut a shaft shoulder. Selection arithmetic: the C0/C ratio is about 1.04 (static 166 kN against dynamic 159 kN), typical of a spherical roller sized for heavy combined loads, and the 18.6 kN fatigue load limit Pu is the equivalent-load floor used in the life calculation. Over-driving the 21310-ek up its sleeve pinches radial clearance below the residual minimum and can crack the inner ring in service; under-driving leaves the sleeve seat loose, so the ring creeps and frets the sleeve — measure, do not estimate.
Typical equipment & failure modes
Common applications
- vibrating screen and scalper main shafts
- conveyor drive and bend pulleys
- fan and pulley shafts that need periodic bearing removal in the field
- shafting produced to commercial tolerances, where the adapter sleeve supplies the precision seat
Known failure patterns
- raceway fatigue spalling of the sphered outer raceway after extended service above the catalogue L10 rating
- inner-ring raceway spalling from edge loading when misalignment exceeds the self-aligning recovery range
- sleeve seizure and shaft seat damage from omitting the anti-seize film between withdrawal sleeve and journal before drive-up
- surface distress and smearing when the relubrication interval is exceeded — the W33 groove is only effective if grease actually reaches the roller rows
- hard-particle indentation of the raceway in unfiltered oil or contaminated grease systems
Selection pitfalls — read before you substitute
- On this 50 mm bore, an interference inner-ring fit consumes a large share of the CN clearance; specify C3 when the inner ring rotates hot, and verify residual clearance after mounting rather than trusting the catalogue clearance class.
- The 21300-series series at 50 mm bore (110×27 mm) pairs a heavy OD with a narrow section — a compact way to add capacity, but the shoulder and abutment diameters differ from the 222 series; it is not a drop-in swap.
- The 21310-ek and its cylindrical-bore counterpart 21310 share envelope and load ratings (159/166 kN) but are not interchangeable in a housing already fitted for direct shaft mounting — the sleeve changes the assembly stack-up.
- The 21310-ek and its cylindrical-bore counterpart 21310 share envelope and load ratings (159/166 kN) but are not interchangeable in a housing already fitted for direct shaft mounting — the sleeve changes the assembly stack-up.
- The self-aligning feature is not a license to ignore alignment: beyond ≈ 0.5–2.5° (series-dependent) the edge loading eats the fatigue margin, and seal drag grows as the rings tilt.
- The 159/166 kN ratings are SKF catalogue values for this tapered-bore execution (SKF 21310 EK); sleeve, KM nut and MB washer are separate order numbers, and the catalogue version (SKF catalogue PUB BU/P1 17000) should travel with the mounting specification.
Frequently asked questions
What are the dimensions and catalogue data of 21310-ek?
The SKF 21310 EK is a double-row spherical roller bearing with a 1:12 tapered bore, 50 mm nominal bore, 110 mm outer diameter and 27 mm width (1.969 × 4.331 × 1.063 in) per ISO 15. From SKF catalogue PUB BU/P1 17000: C 159 kN, C0 166 kN, Pu 18.6 kN, reference speed 5,600 r/min, limiting speed 7,500 r/min, mass about 1600 g. It is mounted on an adapter (H) or withdrawal (AH) sleeve, not directly on the shaft.
What does the K suffix mean on 21310-ek?
K marks a 1:12 tapered bore for sleeve mounting — SKF writes EK or CCK(/W33), FAG writes -K- inside the suffix chain for sleeve mounting. The bearing seats on an H-series adapter sleeve with a KM locknut and MB lock washer (plain shaft, h9 tolerance), or on an AH withdrawal sleeve against a shaft shoulder. The rarer K30 suffix would instead mean a 1:30 taper; dimension series 40/41 spherical rollers commonly use it.
Which adapter sleeve fits the 21310-ek?
The sleeve is selected by the actual shaft diameter in millimetres, not only by the 50 mm nominal bore: SKF H-sleeve numbers each cover a small shaft-diameter range and are width-series specific (H39/H30/H31/H32 matching dimension series 39/40/31/32), and each kit bundles the sleeve, KM locknut and MB lock washer. For shoulder locations use an AH withdrawal sleeve instead. Confirm the sleeve number against the SKF catalogue PUB BU/P1 17000 mounting tables for your shaft size.
How is the 21310-ek driven up and checked?
Mounting is controlled by radial-clearance reduction or axial drive-up distance from the SKF catalogue tables for the 1:12 taper, never by locknut torque. Measure clearance with feeler gauges before and after tightening the KM nut, stop at the tabulated decrease, and lock the MB washer tab. Over-drive removes too much clearance (inner-ring cracking risk); under-drive lets the sleeve creep and fret.
What is the difference between 21310-ek and 21310?
They share the ISO 15 envelope and the same 159/166 kN ratings, but 21310-ek has the 1:12 tapered bore for sleeve mounting on a plain shaft, while 21310 has a cylindrical bore for direct mounting on a machined interference journal (typically k5 with H7 housing). They are separate order numbers, not interchangeable in the same shaft arrangement.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 9.2 adapter-sleeve executions on 2026-09-26. Read our editorial & correction policy.