34306-34478 bearing: complete specifications & equivalents
The 34306-34478 is a ISO 355 radial bearing sized 77.788 x 121.442 x 24.608 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 77.788 mm |
| Outer diameter D | 121.442 mm |
| Width B | 24.608 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 115 kN |
| Basic static load rating C0 | 134 kN |
| Fatigue load limit Pu | 15.3 kN |
| Reference speed (thermal) | 4300 rpm |
| Limiting speed (mechanical) | 5300 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 920 g |
| Manufacturer designation | SKF 34306/34478 |
| Standard | ISO 355 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.2 inch single-row TRB |
| Last verified | 2026-09-28 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.2 inch single-row TRB) · extracted 2026-09-28
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.2 inch 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 & 34000-series range
| Bore d | 3.063 in |
|---|---|
| Outer diameter D | 4.781 in |
| Width B | 0.969 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 21.8 mm |
| Smallest bore in 34000-series | 77.788 mm |
| Largest outer diameter in 34000-series | 121.442 mm |
| Width range across 34000-series | 24.608–24.608 mm |
| Bore position in 34000-series (smallest first) | 1 of 1 |
| Bore above smallest 34000-series size | 0 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 34306-34478-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 77.788×121.442×24.608 mm envelope per ISO 15; catalogue load ratings differ by >10% — re-rate the application before substituting. |
| 34306-34478 | Timken | full Dimensions and internal design equivalent — standard interchange. | Same inch-series cone/cup boundary envelope (d/D/T); load ratings and speed limits are brand-specific and may differ. |
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 34306-34478 model number is decoded
Fit selection follows the rotating ring — interference on a rotating cone — and two 34306 units are required to take reversing thrust; keep the induced axial load inside the rated capacity when calculating the pair. Material and manufacturing detail: the 920 g catalogue mass reflects through-hardened bearing steel (density ~7.85 g/cm³) machined to the 34300 ISO envelope, with the pressed-steel cage contributing roughly 28 g of the total; the 77.788 mm bore is ground to IT5 roundness and the 121.442 mm OD to IT5 cylindricity, and the 24.608 mm width tolerance keeps the pair-setting scatter within the ISO preload class. Cone versus cup responsibility in 34306: the 34306 cone carries the 77.788 mm bore, rollers and pressed-steel cage; the 34478 cup carries the 121.442 mm OD raceway, the roller-seating rib and the outer press-fit surface. The two references are not interchangeable halves.For a 77.788 mm shaft carrying combined load, SKF lists 34306 under catalogue execution SKF 34306/34478: one open single-row tapered roller bearing in the inch 34000-series.Digit by digit, 34306 reads as cone reference / cup reference in the 34000-series inch series; the 77.788 mm bore, 121.442 mm OD and 24.608 mm width are the metric equivalents of the original inch boundary values. The SKF catalogue adds the ISO 355 dimension-series code after the bare number (e.g. ); it is the dimensional series, not a separate part number. Selection arithmetic: the C0/C ratio is about 1.17 (static 134 kN against dynamic 115 kN), typical of a tapered roller sized for axial capacity, and the 15.3 kN fatigue load limit Pu is the equivalent-load floor used in the life calculation.
Typical equipment & failure modes
Common applications
- crane sheave and hoist gearboxes
- paper-machine and printing rolls
- construction machinery drives
- paper-machine and printing rolls
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
- thermal preload runaway in an O-arrangement pair when inner-ring heat expands the setting
- roller large-end smearing against the cone rib after EP lubricant film failure
- cage pocket scoring when the bearing starts cold with grease of too-high base-oil viscosity
- electrical pitting on VFD-driven shafts without grounding protection
Selection pitfalls — read before you substitute
- Mount the 77.788 mm bore 34306 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 320 series at 77.788 mm bore (121.442×24.608 mm) is the low-friction, higher-speed section; it carries less thrust than a 302 of the same bore, so verify the axial load share before swapping.
- At the 115 kN rating of 34306, preload class changes stiffness by tens of percent but also heat generation; select light preload for the 5,300 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 34306 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 115/134 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 34306 (basic, B steeper angle, Q/J2 clearance variants); they are not interchangeable order numbers — quote the full SKF 34306/34478 designation when purchasing and match the execution to the mounting arrangement.
Frequently asked questions
How does 34306 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 34306 position and vice versa — verify load direction, Fa/Fr ratio and speed before substituting.
What shaft and housing fits suit 34306?
For a rotating shaft under normal load, seat the cone on a k5 shaft fit; the cup is usually a loose-to-transition fit in the housing so it can creep slightly and distribute wear. Chamfer and shoulder diameters must clear the bearing rings so the 24.608 mm-wide cup seats square; the mounting setting (end play or preload) is set by the axial position of the cup relative to the cone.
Is 34306 interchangeable with other brands?
Inch-series tapered roller bearings follow a long-standing industry boundary plan, so cones and cups of the same basic number are generally dimensionally interchangeable across manufacturers. However, internal geometry, cage design and load ratings differ by brand, so for paired or precision applications keep both halves of the set from one manufacturer — or re-verify ratings and setting when mixing.
What are the dimensions and catalogue data of 34306?
The SKF 34306/34478 is a single-row tapered roller bearing with 77.788 mm bore, 121.442 mm outer diameter and 24.608 mm width (3.063 × 4.781 × 0.969 in). From SKF catalogue PUB BU/P1 17000: basic dynamic load rating C 115 kN, C0 134 kN, fatigue load limit Pu 15.3 kN, reference speed 4,300 r/min, limiting speed 5,300 r/min, mass about 920 g. It is an open, separable bearing with a pressed-steel cage.
How does the 34306 inch-series designation work?
Inch-series tapered roller bearings use a Timken-style cone/cup convention: the number before the slash identifies the cone (inner ring with roller and cage assembly), the number after the slash identifies the cup (outer ring), and the 34000-series code marks the dimensional series. The metric dimensions 77.788×121.442×24.608 mm are the converted equivalents of the original inch boundary dimensions.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.2 inch single-row TRB on 2026-09-28. Read our editorial & correction policy.