21320-EK bearing: complete specifications & equivalents
The 21320-EK is a ISO 15 radial bearing sized 100 x 215 x 47 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 100 mm |
| Outer diameter D | 215 mm |
| Width B | 47 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 433 kN |
| Basic static load rating C0 | 490 kN |
| Fatigue load limit Pu | 49 kN |
| Reference speed (thermal) | 3400 rpm |
| Limiting speed (mechanical) | 4500 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 10500 g |
| Manufacturer designation | SKF 21320 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 | 3.937 in |
|---|---|
| Outer diameter D | 8.465 in |
| Width B | 1.85 in |
| ISO bore code | 20 |
| Radial section height (D−d)/2 | 57.5 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) | 13 of 14 |
| Bore above smallest 21300-series size | 60 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 21320-NTN | NTN | full Dimensions and internal design equivalent — standard interchange. | Identical ISO 15 envelope, seal and ratings band — standard interchange; re-verify precision class and clearance per supplier. |
| 21320 | SKF | full Dimensions and internal design equivalent — standard interchange. | Tapered-bore (1:12) sleeve-mounted execution of 21320; identical ISO 15 envelope, fits H320 adapter sleeve on a 90 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 21320-EK model number is decoded
In SKF catalogue PUB BU/P1 17000, 21320-ek denotes the tapered-bore version (K suffix, taper 1:12) of the 21300-series spherical roller bearing: dimensioned 100×215×47 mm, it seats on an adapter or withdrawal sleeve rather than directly on a machined journal. Digit by digit, 21320-ek reads as bearing type 2 (spherical roller, two barrel-roller rows), dimension series 13, and bore reference 20 resolving to 100 mm; 215 mm OD and 47 mm width are the matching ISO 15 boundary values. Sleeve mounting is why the K execution exists: a plain h9-tolerance shaft is enough because the adapter sleeve supplies the precision seat, and the bearing is removable without pulling over an interference journal — a separate order number from the cylindrical-bore bearing, never a field conversion. With C 433 kN and C0 490 kN, the 21320-ek load check covers radial plus moderate axial in either direction — but below the minimum load the rollers skid, so verify P ≥ 0.01·C0 at the lightest operating point. Over-driving the 21320-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
- large vibrating screens and feeders
- marine propulsion and thruster shafts
- long through-shafts in conveyors, where a sleeve seat avoids a precision journal
- stepped shafts fitted with withdrawal sleeves against a fixed shoulder
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
- inner-ring circumferential cracking after over-drive on the tapered seat removes too much radial clearance and the bearing runs preloaded
- surface distress and smearing when the relubrication interval is exceeded — the W33 groove is only effective if grease actually reaches the roller rows
- false brinelling on standby machines exposed to external vibration
Selection pitfalls — read before you substitute
- Mount the 100 mm bore 21320-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 100 mm bore (215×47 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 100 mm nominal bearing bore: H-sleeve part numbers span a small diameter range, so two different shaft diameters can use the same 21320-ek with different sleeves.
- The adapter sleeve is selected by actual shaft diameter, not by the 100 mm nominal bearing bore: H-sleeve part numbers span a small diameter range, so two different shaft diameters can use the same 21320-ek with different sleeves.
- Shaft and housing fillets must clear the bearing chamfer so the 47 mm-wide rings seat square; use an undercut or withdrawal groove rather than an oversized radius that locks on the ring face.
- The 433/490 kN ratings are SKF catalogue values for this tapered-bore execution (SKF 21320 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 21320-ek?
The SKF 21320 EK is a double-row spherical roller bearing with a 1:12 tapered bore, 100 mm nominal bore, 215 mm outer diameter and 47 mm width (3.937 × 8.465 × 1.85 in) per ISO 15. From SKF catalogue PUB BU/P1 17000: C 433 kN, C0 490 kN, Pu 49 kN, reference speed 3,400 r/min, limiting speed 4,500 r/min, mass about 10500 g. It is mounted on an adapter (H) or withdrawal (AH) sleeve, not directly on the shaft.
What does the K suffix mean on 21320-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 21320-ek?
The sleeve is selected by the actual shaft diameter in millimetres, not only by the 100 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 21320-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 21320-ek and 21320?
They share the ISO 15 envelope and the same 433/490 kN ratings, but 21320-ek has the 1:12 tapered bore for sleeve mounting on a plain shaft, while 21320 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.