7940 bearing: complete specifications & equivalents
The 7940 is a ISO 15 radial bearing sized 200 x 280 x 38 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 200 mm |
| Outer diameter D | 280 mm |
| Width B | 38 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | brass |
| Basic dynamic load rating C | 205 kN |
| Basic static load rating C0 | 231 kN |
| Fatigue load limit Pu | 9.9 kN |
| Limiting speed (mechanical) | 2200 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 7150 g |
| Manufacturer designation | NTN 7940 |
| 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 & 7900-series range
| Bore d | 7.874 in |
|---|---|
| Outer diameter D | 11.024 in |
| Width B | 1.496 in |
| ISO bore code | 40 |
| Radial section height (D−d)/2 | 40 mm |
| Smallest bore in 7900-series | 25 mm |
| Largest outer diameter in 7900-series | 420 mm |
| Width range across 7900-series | 9–56 mm |
| Bore position in 7900-series (smallest first) | 27 of 32 |
| Bore above smallest 7900-series size | 175 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 7940 | ISO 15 | full Dimensions and internal design equivalent — standard interchange. | ISO 15 boundary-dimension envelope; standard interchange — confirm clearance class and precision with the supplier. |
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 7940 model number is decoded
At 200 x 280 x 38 mm, NTN 7940 sits in the extra-light, high-speed 7900 single-row family of the angular-contact programme. NTN builds the number from 79 is the single-row dimension series (extra-light, high-speed 7900 single-row family), then 40 encodes the 200 mm bore (bore code x 5); with no letter after the digits it is the standard 30 deg contact-angle execution — the 40 deg version carries a B. The static margin, C0 231 kN versus C 205 kN, is what supports slow oscillating duty and shock without immediate brinelling. Against a deep-groove bearing of the same 200 mm bore, this bearing trades some pure-radial comfort for real one-direction thrust capacity and higher running accuracy. Heat-mounting to 80-90 deg C is the clean route onto a 200 mm shaft; drive-fits through the balls transmit force through the contact ellipse and can brinell it.
Typical equipment & failure modes
Common applications
- crusher and mill pinion shafts
- large pump and turbine auxiliary shafts
- steel-plant conveyor and table roll drives
- wind-turbine and heavy-machinery auxiliaries
Known failure patterns
- impact brinelling dents on the 30 deg contact path after a shaft-side hammer blow during mounting, because axial shock travels straight through the contact angle
- loss of preload after housing-fret or shaft creep, leaving the pair loose — ball skidding, cage rattle and a falling natural frequency follow
- resin-cage cracking on the 7900-series sizes after hot, dry running or solvent attack on the polymer
- lubricant starvation scoring at the ball/raceway contact when grease volume or relubrication interval is guessed instead of calculated
- flaking that starts at the raceway shoulder on the thrust-loaded side when axial load repeatedly exceeds the design share
Selection pitfalls — read before you substitute
- At this size the shaft fit, shoulder geometry and preload procedure dominate the outcome; a 200 mm bore bearing forgives nothing in a poorly machined housing.
- The 7900 extra-light section is chosen for speed and stiffness, not for load margin — check that C0 231 kN really covers the worst static case before substituting it for a 7000.
- On a 200 mm shaft, an interference fit eats internal clearance; skipping the clearance/preload recalculation is the classic cause of a new bearing running 20 deg C hotter than the drawing suggests.
- A single-row angular contact left loose on the shaft to "help assembly" will fret the seat: the contact angle keeps driving the ring axially under load.
- Do not pair two random 7940 bearings from stock and expect catalogue paired ratings — matched-set grinding is what makes DB/DF/DT preload behave, and NTN sells those as separate order numbers.
- The 205/231 kN ratings and 9.9 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 7940; internal geometry legitimately differs between manufacturers, so re-verify ratings, contact angle and suffix before substituting another make on a rated drive.
Frequently asked questions
What are the dimensions and catalogue ratings of NTN 7940?
7940 is a single-row angular contact ball bearing to ISO 15: 200 mm bore, 280 mm outside diameter, 38 mm width (7.874 x 11.024 x 1.496 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 205 kN, C0 231 kN and a 9.9 kN fatigue load limit Pu; the grease limiting speed is 2,200 r/min and the oil rating 3,000 r/min; mass about 7150 g.
How is the 7940 designation structured?
79 is the single-row dimension series (extra-light, high-speed 7900 single-row family); 40 encodes the 200 mm bore (bore code x 5); with no letter after the digits it is the standard 30 deg contact-angle execution — the 40 deg version carries a B. The 280 mm OD and 38 mm width follow the ISO 15 boundary-dimension plan for that series.
Which axial direction does 7940 support?
One 7940 alone takes thrust in one direction only, along its 30 deg contact angle; reversing thrust calls for a second bearing or a factory-matched DB/DF/DT pair (the catalogue right-hand columns list the paired ratings). Radial load is always carried as a combined load through the angled contact.
What lubrication speeds does NTN print for 7940?
Per NTN Ball and Roller Bearings CAT.No.2203E, the grease limiting speed is 2,200 r/min and the oil rating 3,000 r/min. These are catalogue ceilings for a correctly mounted bearing with the stated lubricant; preload, fill quantity, ambient heat and paired arrangements all move the real limit.
What should be checked before substituting another make for 7940?
The 200/280/38 mm envelope is ISO 15 interchangeable, but internal geometry — contact angle, osculation, cage and shoulder details — is maker-specific. Re-verify C 205 kN / C0 231 kN, the speed figures, contact angle and suffix meaning against the donor catalogue before swapping on a rated drive.
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.