31315 bearing: complete specifications & equivalents
The 31315 is a ISO 355 radial bearing sized 75 x 160 x 40 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 75 mm |
| Outer diameter D | 160 mm |
| Width B | 40 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 255 kN |
| Basic static load rating C0 | 245 kN |
| Fatigue load limit Pu | 29 kN |
| Reference speed (thermal) | 3200 rpm |
| Limiting speed (mechanical) | 4300 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 3400 g |
| Manufacturer designation | SKF 31315 |
| Standard | ISO 355 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.1 metric single-row TRB |
| Last verified | 2026-09-26 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.1 metric single-row TRB) · extracted 2026-09-26
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.1 metric single-row TRB); 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 & 31300-series range
| Bore d | 2.953 in |
|---|---|
| Outer diameter D | 6.299 in |
| Width B | 1.575 in |
| ISO bore code | 15 |
| Radial section height (D−d)/2 | 42.5 mm |
| Smallest bore in 31300-series | 25 mm |
| Largest outer diameter in 31300-series | 320 mm |
| Width range across 31300-series | 18.25–82 mm |
| Bore position in 31300-series (smallest first) | 11 of 22 |
| Bore above smallest 31300-series size | 50 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 31315 | ISO 15 | full Dimensions and internal design equivalent — standard interchange. | ISO 355 boundary-dimension envelope; brand-specific OEM equivalents (NSK/FAG/NTN) pending multi-source data. |
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 31315 model number is decoded
The SKF 31315 is a 75×160×40 mm single-row tapered roller bearing — the steep-angle heavy section entry in the 31300 series, with an asymmetric raceway cut for thrust capacity and separable mounting.On the SKF nameplate, 31315 follows the ISO 355 convention: 3 for the tapered-roller type, 13 for the steep-angle heavy section, final digits 15 for the 75 mm bore. SKF lists the plain number as the basic execution; letter suffixes such as B denote a steeper contact angle and are different order numbers. Selection arithmetic: the C0/C ratio is about 0.96 (static 245 kN against dynamic 255 kN), typical of a tapered roller sized for axial capacity, and the 29 kN fatigue load limit Pu is the equivalent-load floor used in the life calculation. Specify pairs rather than single units wherever thrust reverses: the tapered contact of 31315 generates an induced axial load under radial force, and an unpaired bearing on a reversing shaft will run slack and fret its seat.
Typical equipment & failure modes
Common applications
- heavy industrial gearboxes and speed reducers
- large process pump and compressor shafts
- rolling-mill auxiliary drives
- crane sheave and hoist gearboxes
Known failure patterns
- cup or cone misalignment when the separable rings are not seated square during mounting
- loose cup rotation in the housing when the specified press fit is not achieved
- preload loss as the mounted pair relaxes, letting rollers skid and smear the raceways
- axial overload spalling at the roller-rib contact beyond the single-row thrust rating
- cage pocket scoring when the bearing starts cold with grease of too-high base-oil viscosity
- rib-roller contact scoring from loss of the EP additive film
Selection pitfalls — read before you substitute
- Mount the 75 mm bore 31315 by induction heating of the cone (max 120 °C — the pressed-steel cage sets the ceiling, not the steel); driving it home through the cup or rollers brinells the tapered raceway.
- The 313 series at 75 mm bore (160×40 mm) has a steeper contact angle than the 302/303 families — higher axial capacity per radial load but more induced thrust and heat; do not interchange with a 30315 without re-running the pair calculation.
- At the 255 kN rating of 31315, preload class changes stiffness by tens of percent but also heat generation; select light preload for the 4,300 r/min speed end and heavier preload only where moment stiffness dominates.
- O (back-to-back) pairs are stiffer against moments, X (face-to-face) pairs tolerate misalignment and thermal growth better; choosing the arrangement from the 2D drawing rather than the actual shaft thermal expansion is a common 31315 mounting error.
- The pressed-steel cage is rated for standard industrial service; sustained running above the limiting speed or with degraded lubricant wears the cage pockets — inspect the cage at every relubrication interval.
- The 255/245 kN ratings are SKF catalogue 17000 values for the basic execution; SKF can revise internal geometry without changing the order number, so keep the catalogue version (PUB BU/P1 17000/1 EN, 2018) with the specification and re-verify for critical drives.
- SKF lists several executions of 31315 (basic, B steeper angle, Q/J2 clearance variants); they are not interchangeable order numbers — quote the full SKF 31315 designation when purchasing and match the execution to the mounting arrangement.
Frequently asked questions
What are the dimensions and catalogue data of 31315?
The SKF 31315 is a single-row tapered roller bearing with 75 mm bore, 160 mm outer diameter and 40 mm width (2.953 × 6.299 × 1.575 in) per ISO 355. From SKF catalogue PUB BU/P1 17000: basic dynamic load rating C 255 kN, C0 245 kN, fatigue load limit Pu 29 kN, reference speed 3,200 r/min, limiting speed 4,300 r/min, mass about 3400 g. It is an open, separable bearing with a pressed-steel cage.
How does the 31315 bore code work?
The last two digits of 31315 are bore code 15, so 15 × 5 = 75 mm bore. The 160 mm OD and 40 mm width come from the ISO 355 dimension-series plan, shared with other tapered bearings of the same code.
What do the 31315 series and basic execution designations mean?
The leading 3 marks a single-row tapered roller bearing; the second digit 13 is the ISO 355 series (steep-angle heavy section). The SKF catalogue lists the ISO 355 dimension-series code after the bare number. A steeper-contact-angle variant (B suffix) is a different order number and is not interchangeable with the basic execution.
Can a single 31315 take axial load in both directions?
No — one single-row tapered roller bearing reacts thrust in one direction only, and under radial load its contact angle induces an axial force. Use two bearings as a matched pair: O (back-to-back) for a rigid, moment-resisting arrangement, X (face-to-face) where thermal expansion must be tolerated, or tandem where one-direction thrust is shared.
How does 31315 compare with a ball bearing of the same bore?
A tapered roller bearing has line contact and a steep contact angle: much higher combined axial-plus-radial capacity and shock resistance than a ball bearing of the same bore, at the cost of speed, one-direction thrust, mandatory pairing for reversing loads and a minimum axial load requirement. A ball bearing cannot be dropped into a combined-load 31315 position and vice versa — verify load direction, Fa/Fr ratio and speed before substituting.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.1 metric single-row TRB on 2026-09-26. Read our editorial & correction policy.