NU20-850-ECMA bearing: complete specifications & equivalents
The NU20-850-ECMA is a ISO 15 radial bearing sized 850 x 1220 x 212 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 850 mm |
| Outer diameter D | 1220 mm |
| Width B | 212 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | brass |
| Basic dynamic load rating C | 8420 kN |
| Basic static load rating C0 | 18600 kN |
| Fatigue load limit Pu | 1200 kN |
| Reference speed (thermal) | 360 rpm |
| Limiting speed (mechanical) | 560 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 880000 g |
| Manufacturer designation | SKF NU 20/850 ECMA |
| Standard | ISO 15 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 6.1 single-row cylindrical roller bearings |
| Last verified | 2026-09-26 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 6.1 single-row cylindrical roller bearings) · extracted 2026-09-26
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 6.1 single-row cylindrical roller bearings); 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 & NU2000-series range
| Bore d | 33.465 in |
|---|---|
| Outer diameter D | 48.031 in |
| Width B | 8.346 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 185 mm |
| Smallest bore in NU2000-series | 300 mm |
| Largest outer diameter in NU2000-series | 1220 mm |
| Width range across NU2000-series | 95–212 mm |
| Bore position in NU2000-series (smallest first) | 12 of 12 |
| Bore above smallest NU2000-series size | 550 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the NU20-850-ECMA model number is decoded
For a 850 mm shaft, SKF lists NU20-850-ECMA as single-row caged cylindrical roller: 1220 mm OD, 212 mm wide, Pu 1200 kN, the catalogue lists 360 r/min thermal reference speed and 560 r/min mechanical limiting speed. The NU configuration means two integral flanges on the outer ring and no flanges on the inner ring, so the inner ring together with the roller set is separable; functionally the bearing is non-locating: the inner ring assembly can float axially in both directions and the bearing cannot support axial load. The ECMA suffix denotes the E-design execution with a one-piece machined brass cage for higher-temperature and higher-speed continuous duty. The one-piece machined brass cage is reflected in the published speeds and temperature limits. Selection arithmetic: C0/C ≈ 2.21 (18600 against 8420 kN), and the Pu figure 1200 kN is the fatigue load-limit floor for the SKF life equation; the catalogue lists 360 r/min thermal reference speed and 560 r/min mechanical limiting speed. Assembly note: fit the inner ring and roller assembly onto the shaft and the outer ring into the housing independently; thermal expansion is absorbed by axial float, so do not trap the inner ring between shaft shoulders. Heat steel rings inductively to max 120 °C.
Typical equipment & failure modes
Common applications
- large rolling-mill drive trains
- marine propulsion line shafts
- heavy turbogenerator rotor supports
- mining hoist and winder shafts
Known failure patterns
- inner-ring raceway spalling from overload or contamination in the line-contact hertz zone
- outer-ring raceway fatigue after extended service at loads above the catalogue L10 rating
- cage pocket wear from roller skew at light load
- cage pocket wear from roller skidding at insufficient radial load or during start-up before oil film build-up
- roller-end scoring from inadequate oil flow in the roller-raceway contact
- edge-loading fatigue after shaft deflection beyond the 3–4 minute alignment limit
- false brinelling on standby machines exposed to external vibration
Selection pitfalls — read before you substitute
- Do not use a NU bearing where axial load must be carried — the design carries radial load only
- The dimension series 20 (light section for large shafts) envelope is shared with the N/NU/NJ/NUP executions of 20/850, but flange configuration and axial-locating behaviour differ — quote the full SKF NU 20/850 ECMA and do not substitute rib styles without checking the shaft locating scheme.
- Press-fit force goes through ring faces only; driving a ring home through the rollers brinells the 1220 mm raceway.
- Press-fit force goes through ring faces only; driving a ring home through the rollers brinells the 1220 mm raceway.
- The 8420/18600 kN ratings are SKF catalogue 17000 (2018) values for the ECMA execution; re-verify against the current catalogue for critical drives and keep the catalogue version with the specification.
Frequently asked questions
What are the dimensions and catalogue data of NU20-850-ECMA?
SKF NU 20/850 ECMA is a single-row caged cylindrical roller bearing with 850 mm bore, 1220 mm OD and 212 mm width per ISO 15. SKF lists C 8420 kN, C0 18600 kN, Pu 1200 kN, reference speed 360 r/min and limiting speed 560 r/min, mass about 880000 g.
What does the NU designation and ECMA suffix mean?
The ECMA suffix denotes the E-design execution with a one-piece machined brass cage for higher-temperature and higher-speed continuous duty. Structurally this execution has two integral flanges on the outer ring and no flanges on the inner ring, so the inner ring together with the roller set is separable.
Can NU20-850-ECMA take axial load and locate the shaft?
No — the inner ring has no flanges, so the NU bearing is non-locating and carries radial load only; use NJ (one direction), NUP (both directions) or a paired thrust bearing for axial duty.
How does NU20-850-ECMA compare with the other executions in the same envelope?
The N/NU/NJ/NUP executions share the ISO 15 envelope and load ratings but differ in flange arrangement and axial-locating behaviour; quote the exact order number.
What limits the service life of this bearing most often?
Line-contact fatigue above the L10 rating, cage wear at light loads and high temperatures, and edge loading from misalignment beyond about 3–4 minutes of arc are the typical failure drivers.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 6.1 single-row cylindrical roller bearings on 2026-09-26. Read our editorial & correction policy.