21312-EK bearing: complete specifications & equivalents
The 21312-EK is a ISO 15 radial bearing sized 60 x 130 x 31 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 60 mm |
| Outer diameter D | 130 mm |
| Width B | 31 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 217 kN |
| Basic static load rating C0 | 240 kN |
| Fatigue load limit Pu | 26.5 kN |
| Reference speed (thermal) | 4800 rpm |
| Limiting speed (mechanical) | 6300 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 2350 g |
| Manufacturer designation | SKF 21312 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 | 2.362 in |
|---|---|
| Outer diameter D | 5.118 in |
| Width B | 1.22 in |
| ISO bore code | 12 |
| Radial section height (D−d)/2 | 35 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) | 5 of 14 |
| Bore above smallest 21300-series size | 20 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 21312-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 60×130×31 mm envelope per ISO 15; catalogue load ratings differ by >10% — re-rate the application before substituting. |
| 21312 | SKF | full Dimensions and internal design equivalent — standard interchange. | Tapered-bore (1:12) sleeve-mounted execution of 21312; identical ISO 15 envelope, fits H312 adapter sleeve on a 55 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 21312-EK model number is decoded
21312-ek is the 1:12 tapered-bore execution of the 21300-series spherical roller bearing: the same two barrel-roller rows on a sphered outer raceway as 21312, but the inner-ring bore tapers 1 mm per 12 mm for adapter- or withdrawal-sleeve mounting, as listed by SKF in SKF catalogue PUB BU/P1 17000. On the SKF nameplate, 21312-ek follows the ISO 15 convention: 2 for the spherical roller type, 13 for the dimension series 13 (heavy OD, normal width), final digits 12 for the 60 mm bore. Reading the suffix on 21312-ek, the K (or EK/CCK) element changes only the bore — 1:12 taper for sleeve mounting — while the rest of the suffix chain (CC cages with W33 groove) keeps the same internal design, cage and W33 relubrication features as the cylindrical-bore 21312. At 4,800 r/min reference speed the 35.0 mm-section 21312-ek is governed thermally by lubricant flow through the W33 groove and the two-row roller complement; grease or oil selection should be made against that value, with 6,300 r/min as the mechanical ceiling. On an H adapter sleeve the 60 mm shaft seat only needs an h9 plain journal; slide the sleeve into the 21312-ek inner ring, tighten the KM nut against the MB washer until the catalogue clearance-reduction value is reached, then lock the washer tab.
Typical equipment & failure modes
Common applications
- heavy conveyor head shafts in mining
- jaw and cone crusher main shafts
- shafting produced to commercial tolerances, where the adapter sleeve supplies the precision seat
- split-housing plummer block arrangements with bearings swapped in situ
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
- roller-end scoring from starved lubricant at start-up before the grease channel purges
- brinelling from static overload or impact during handling and mounting
Selection pitfalls — read before you substitute
- Mount the 60 mm bore 21312-ek by induction heating (max 120 °C) or oil injection — driving a bearing of this section home through the rollers brinells both raceways, and the damage only speaks up as vibration hours later.
- The 21300-series series at 60 mm bore (130×31 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 adapter sleeve is selected by actual shaft diameter, not by the 60 mm nominal bearing bore: H-sleeve part numbers span a small diameter range, so two different shaft diameters can use the same 21312-ek with different sleeves.
- Never apply the drive-up or clearance-reduction figures for this 1:12 tapered 21312-ek to a bearing of the other taper (1:12 vs 1:30); the steeper taper moves far less clearance per nut turn and the targets come from different catalogue tables.
- 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 217/240 kN ratings are SKF catalogue values for this tapered-bore execution (SKF 21312 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 21312-ek?
The SKF 21312 EK is a double-row spherical roller bearing with a 1:12 tapered bore, 60 mm nominal bore, 130 mm outer diameter and 31 mm width (2.362 × 5.118 × 1.22 in) per ISO 15. From SKF catalogue PUB BU/P1 17000: C 217 kN, C0 240 kN, Pu 26.5 kN, reference speed 4,800 r/min, limiting speed 6,300 r/min, mass about 2350 g. It is mounted on an adapter (H) or withdrawal (AH) sleeve, not directly on the shaft.
What does the K suffix mean on 21312-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 21312-ek?
The sleeve is selected by the actual shaft diameter in millimetres, not only by the 60 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 21312-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 21312-ek and 21312?
They share the ISO 15 envelope and the same 217/240 kN ratings, but 21312-ek has the 1:12 tapered bore for sleeve mounting on a plain shaft, while 21312 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.