231-670B bearing: complete specifications & equivalents
The 231-670B is a ISO 15 radial bearing sized 670 x 1090 x 336 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 670 mm |
| Outer diameter D | 1090 mm |
| Width B | 336 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 12500 kN |
| Basic static load rating C0 | 23600 kN |
| Fatigue load limit Pu | 1400 kN |
| Limiting speed (mechanical) | 230 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1250000 g |
| Manufacturer designation | NTN 231/670B |
| 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 & 23100-series range
| Bore d | 26.378 in |
|---|---|
| Outer diameter D | 42.913 in |
| Width B | 13.228 in |
| ISO bore code | 31 |
| Radial section height (D−d)/2 | 210 mm |
| Smallest bore in 23100-series | 100 mm |
| Largest outer diameter in 23100-series | 1420 mm |
| Width range across 23100-series | 52–412 mm |
| Bore position in 23100-series (smallest first) | 31 of 36 |
| Bore above smallest 23100-series size | 570 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 231-670BK | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same NTN 23100-series envelope, cage and ratings; this is the cylindrical-bore execution of the tapered-bore 231-670BK (K/K30 sleeve or tapered-seat mounting). 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 231-670B model number is decoded
In NTN Ball and Roller Bearings CAT.No.2203E, 231/670B denotes the 670 mm bore spherical roller bearing (12500 kN C / 23600 kN C0) in the 23100 series, the self-aligning choice for heavy combined load. Digit by digit the code reads as spherical-roller dimension series plus 670 mm bore; the 336 mm width is the wide ISO 15 section, which is why spherical rollers interchange dimensionally but not in cage or rating detail. The cylindrical bore fits a machined 670 mm shaft seat directly; the same envelope in 231/670BK (tapered) is the sleeve-mounted alternative when clearance must be set by drive-up. Equivalent-load planning keeps a radial plus moderate axial combination on 231/670B; if the axial component dominates, pair with a thrust bearing rather than running one roller row unloaded. After mounting on a tapered seat, lock the nut and re-check clearance after a short running-in period, because sleeve seating and ring lift-off can change the residual clearance of the 670 mm set.
Typical equipment & failure modes
Common applications
- steel-mill and heavy crusher main shafts
- mining shovel and dragline swing shafts
- cement-rotary-kiln support and trunnion rolls
- large SAG/ball-mill trunnion and pinion shafts
Known failure patterns
- lubricant starvation at the centre rib area when the D1/W33 groove is not connected to a relubrication supply
- pressed EA cage fatigue under sustained vibration when minimum load is not maintained
- micro-pitting when the EHL film is thinner than the raceway composite roughness
- fretting corrosion between adapter sleeve and tapered bore when the drive-up is insufficient
- false brinelling on stopped machines exposed to screen or crusher vibration
Selection pitfalls — read before you substitute
- At 670 mm bore 231/670B is normally mounted on adapter/withdrawal sleeves with hydraulic assistance; follow the NTN drive-up angle or oil-injection procedure — manual nut tightening cannot set the multi-tonne seating correctly.
- Oil relubrication toward 300 r/min needs drain and level design; flooding the 336 mm cavity churns heat through the heavy roller set and cage despite the higher oil speed figure.
- Adapter-sleeve mounting requires the correct sleeve series and locknut for the 670 mm shaft; a sleeve sized to bore alone ignores thread, width and the oil-injection option on large K30 seats.
- Self-aligning does not mean unlimited misalignment: beyond the catalogue angle the outer ring's spherical travel is exhausted and the 12500 kN rating no longer applies.
- Do not confuse EA and EM at the same number: 231/670B carries basic; swapping to the other cage execution changes mass, speed behaviour and sometimes suitability for vibration, even though the 670×1090 mm envelope is identical.
- The 12500/23600 kN ratings, 1400 kN Pu and 1250000 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for 231/670B (basic); 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 231/670B?
231/670B is an NTN double-row spherical roller bearing to ISO 15: 670 mm bore, 1090 mm OD and 336 mm width (26.378 × 42.913 × 13.228 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 12500 kN, C0 23600 kN, Pu 1400 kN, grease limiting speed 230 r/min, oil 300 r/min, mass about 1250000 g. It is open, with pressed-steel cage (standard execution).
What is the difference between the K/K30 tapered bore and the cylindrical bore versions?
231/670B has a cylindrical bore and mounts directly on a machined shaft seat. Its tapered-bore counterpart is 231/670BK (K = 1:12, or K30 = 1:30 on the wide series), intended for adapter/withdrawal-sleeve mounting.
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. 231/670B is the basic execution.
What do D1 and W33 mean on 231/670B?
231/670B 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 231/670B take?
The sphered outer raceway compensates static and dynamic misalignment in the order of 1–2° (verify the exact 2203E figure for the 23100 series); beyond that, load concentrates on one roller row. Load is predominantly radial with a moderate axial share in either direction — 12500 kN C / 23600 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.