749A-742 bearing: complete specifications & equivalents
The 749A-742 is a ISO 355 radial bearing sized 82.55 x 150.089 x 44.45 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 82.55 mm |
| Outer diameter D | 150.089 mm |
| Width B | 44.45 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 351 kN |
| Basic static load rating C0 | 405 kN |
| Fatigue load limit Pu | 46.5 kN |
| Reference speed (thermal) | 3600 rpm |
| Limiting speed (mechanical) | 4300 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 3400 g |
| Manufacturer designation | SKF 749 A/742 |
| 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 & 745-series range
| Bore d | 3.25 in |
|---|---|
| Outer diameter D | 5.909 in |
| Width B | 1.75 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 33.8 mm |
| Smallest bore in 745-series | 82.55 mm |
| Largest outer diameter in 745-series | 150.089 mm |
| Width range across 745-series | 44.45–44.45 mm |
| Bore position in 745-series (smallest first) | 1 of 1 |
| Bore above smallest 745-series size | 0 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 749A-742-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 82.55×150.089×44.45 mm envelope per ISO 15; catalogue load ratings differ by >10% — re-rate the application before substituting. |
| 749A-742 | 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 749A-742 model number is decoded
SKF lists the plain number as the basic execution; letter suffixes such as B denote a steeper contact angle and are different order numbers. The 46.5 kN Pu figure feeds the adjusted-life equation at contaminated or partial-film conditions, and the 1.15 C0/C balance shows this execution is tuned to thrust-heavy combined loads rather than pure radial running. Specify pairs rather than single units wherever thrust reverses: the tapered contact of 749A generates an induced axial load under radial force, and an unpaired bearing on a reversing shaft will run slack and fret its seat. Dimensional interchange map: within the 74900 series at 82.55 mm bore, the 150.089 mm OD and 44.45 mm width are fixed by the ISO 355 plan, so any same-code bearing from another brand shares the mounting envelope; the 33.8 mm section height distinguishes this family from a 302 or 322 of the same bore, and the 3400 g mass is the minimum—sealed or snap-ring executions add rotating weight above that catalogue baseline. Within the 745-series tables, 749 A appears in several rows because SKF lists multiple cup options for the same cone. 749A is the 742 variant, with 150.089 mm OD and 44.45 mm width; neighbouring rows on the same cone differ only in the cup but are separate orderable bearings.SKF 749A (SKF 749 A/742) is the 745-series tapered roller choice for a 82.55 mm shaft — one row of tapered rollers on an asymmetric raceway inside the 150.089×44.45 mm envelope.The 745-series series assigns 82.55 mm bore, 150.089 mm OD and 44.45 mm width to 749A; the cone and cup references are not interchangeable with other inch-series pairs even when the bore matches, because the cup profile and rib geometry are series-specific.
Typical equipment & failure modes
Common applications
- crane sheave and hoist gearboxes
- paper-machine and printing rolls
- construction machinery drives
- heavy industrial gearboxes and speed reducers
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
- uneven load sharing in a pair when spacer faces are not parallel to the bore
- 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
- fretting corrosion on a loose rotating shaft seat
Selection pitfalls — read before you substitute
- Mount the 82.55 mm bore 749A 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 745-series inch series at 82.55 mm bore (150.089×44.45 mm) follows the Timken cone/cup convention; substitutions must match both the cone and cup reference exactly — interchanging with another series or a metric 3xxxx bearing of the same bore changes OD, width and contact angle, so re-run the pair setting and shoulder-diameter checks before swapping.
- When the outer ring rotates, reverse the fit logic and provide cup location; the tapered contact of 749A pushes the rings apart under load, so a non-located cup walks its seat even when the shaft is fixed.
- Setting is a design value, not an assembly feel: excessive preload in the 749A pair raises operating temperature and can trigger thermal runaway, while too little lets the rollers skid and smear the raceway under light load.
- Shaft and housing fillets must clear the bearing chamfer so the 44.45 mm-wide cup seats square; use an undercut or withdrawal groove rather than an oversized radius that locks on the ring face.
- The 351/405 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 749A (basic, B steeper angle, Q/J2 clearance variants); they are not interchangeable order numbers — quote the full SKF 749 A/742 designation when purchasing and match the execution to the mounting arrangement.
Frequently asked questions
What do the cone and cup numbers in 749A mean?
The cone number (before the slash) identifies the inner ring, rollers and cage; the cup number (after the slash) identifies the outer ring. Both are quoted together because a single-row tapered roller bearing is a matched separable pair — the cone and cup are ground to work together and are not interchangeable with arbitrary other parts. The series prefix (745-series) groups sizes that share the same boundary-dimension plan.
Can a single 749A 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 749A 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 749A position and vice versa — verify load direction, Fa/Fr ratio and speed before substituting.
What shaft and housing fits suit 749A?
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 44.45 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 749A 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.
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.