7948 bearing: complete specifications & equivalents
The 7948 is a ISO 15 radial bearing sized 240 x 320 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 | 240 mm |
| Outer diameter D | 320 mm |
| Width B | 38 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | brass |
| Basic dynamic load rating C | 213 kN |
| Basic static load rating C0 | 255 kN |
| Fatigue load limit Pu | 10.1 kN |
| Limiting speed (mechanical) | 1800 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 8340 g |
| Manufacturer designation | NTN 7948 |
| 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 | 9.449 in |
|---|---|
| Outer diameter D | 12.598 in |
| Width B | 1.496 in |
| ISO bore code | 48 |
| 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) | 29 of 32 |
| Bore above smallest 7900-series size | 215 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 7948 | 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 7948 model number is decoded
7948 is the 240 mm bore member of NTN's extra-light, high-speed 7900 single-row family, with a 320 mm outside diameter and 38 mm section width. Two fields make up the code — 79 is the single-row dimension series (extra-light, high-speed 7900 single-row family) and 48 encodes the 240 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 30 deg contact angle is the lever that turns the 255 kN static rating into useful one-direction thrust capacity. For a 240 mm shaft with combined load, the practical shortlist is this series, its 7000-series standard section, and — where thrust reverses — a back-to-back pair rather than a single row. Mount with the thrust against the marked face: the contact angle runs from the low shoulder of the inner ring to the high shoulder of the outer ring, and reversing it throws the capacity away.
Typical equipment & failure modes
Common applications
- steel-plant conveyor and table roll drives
- wind-turbine and heavy-machinery auxiliaries
- heavy industrial gearbox main shafts
- large fan, blower and turbo-compressor rotors
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
- pressed-steel cage pocket wear and rivet loosening after repeated ball skid at light load and high speed
- flaking that starts at the raceway shoulder on the thrust-loaded side when axial load repeatedly exceeds the design share
- contamination-induced denting — hard particles rolled into the contact ellipse become the initiation points for surface fatigue
Selection pitfalls — read before you substitute
- At this size the shaft fit, shoulder geometry and preload procedure dominate the outcome; a 240 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 255 kN really covers the worst static case before substituting it for a 7000.
- If the application vibrates at standstill (transport, idle machine next to a running line), specify protection: the contact ellipse of a preloaded bearing false-brinells faster than a loose one.
- The 1,800 r/min speed figure assumes the catalogue lubrication state and a correctly set pair; real limits drop fast with excess grease fill or heavy preload.
- A 7948 mounted the wrong way round still turns smoothly by hand; the failure shows up weeks later as raceway flaking on the unloaded-looking side.
- The 213/255 kN ratings and 10.1 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 7948; 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 7948?
7948 is a single-row angular contact ball bearing to ISO 15: 240 mm bore, 320 mm outside diameter, 38 mm width (9.449 x 12.598 x 1.496 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 213 kN, C0 255 kN and a 10.1 kN fatigue load limit Pu; the grease limiting speed is 1,800 r/min and the oil rating 2,400 r/min; mass about 8340 g.
How is the 7948 designation structured?
79 is the single-row dimension series (extra-light, high-speed 7900 single-row family); 48 encodes the 240 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 320 mm OD and 38 mm width follow the ISO 15 boundary-dimension plan for that series.
Which axial direction does 7948 support?
One 7948 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 7948?
Per NTN Ball and Roller Bearings CAT.No.2203E, the grease limiting speed is 1,800 r/min and the oil rating 2,400 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 7948?
The 240/320/38 mm envelope is ISO 15 interchangeable, but internal geometry — contact angle, osculation, cage and shoulder details — is maker-specific. Re-verify C 213 kN / C0 255 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.