344-332AA bearing: complete specifications & equivalents
The 344-332AA is a ISO 355 radial bearing sized 40 x 80 x 21 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 40 mm |
| Outer diameter D | 80 mm |
| Width B | 21 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 87.6 kN |
| Basic static load rating C0 | 80 kN |
| Fatigue load limit Pu | 9.15 kN |
| Reference speed (thermal) | 7000 rpm |
| Limiting speed (mechanical) | 8500 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 470 g |
| Manufacturer designation | SKF 344/332 AA |
| 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 & 335-series range
| Bore d | 1.575 in |
|---|---|
| Outer diameter D | 3.15 in |
| Width B | 0.827 in |
| ISO bore code | 44 |
| Radial section height (D−d)/2 | 20 mm |
| Smallest bore in 335-series | 40 mm |
| Largest outer diameter in 335-series | 80 mm |
| Width range across 335-series | 21–21 mm |
| Bore position in 335-series (smallest first) | 1 of 1 |
| Bore above smallest 335-series size | 0 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 344-332-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×80×21 mm envelope per ISO 15; catalogue load ratings differ by >10% — re-rate the application before substituting. |
| 344-332AA | 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 344-332AA model number is decoded
At 7,000 r/min reference speed the 20.0 mm-section 344 is governed thermally by preload and lubricant flow; grease or oil selection should be made against that value, with 8,500 r/min as the mechanical ceiling. Because the contact line is tapered, one 344 reacts thrust in a single direction; bidirectional shafts need an O or X pair, and a rotating cone on a 40 mm shaft typically takes a k5 seat with an H7 housing bore. Dimensional interchange map: within the 34400 series at 40 mm bore, the 80 mm OD and 21 mm width are fixed by the ISO 355 plan, so any same-code bearing from another brand shares the mounting envelope; the 20.0 mm section height distinguishes this family from a 302 or 322 of the same bore, and the 470 g mass is the minimum—sealed or snap-ring executions add rotating weight above that catalogue baseline. From a specification standpoint the 332 AA cup is the controlling half of 344 for housing design — it sets the 80 mm OD and the outer abutment diameter — while the 344 cone controls shaft fit at the 40 mm bore; the 21 mm width is the result of the two together.344 is a single-row tapered roller bearing in the 335-series inch series: a separable cone-and-cup design for combined radial and one-direction axial load, listed by SKF in SKF catalogue PUB BU/P1 17000.Numbering ties the bearing to its inch-series envelope: 344 means a cone and cup matched pair in the 335-series series — which is why the 40×80×21 mm outline swaps dimensionally with other inch-series bearings of the same code. 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.
Typical equipment & failure modes
Common applications
- pump and compressor shafts
- machine-tool spindles
- belt-driven fan and blower shafts
- differential and pinion drives
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
- 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
- brinelling from pressing the cone or cup home through the rollers
Selection pitfalls — read before you substitute
- On this 40 mm bore, interference and temperature rise consume clearance inside a preloaded pair; calculate the residual clearance after mounting and at operating temperature — an over-tight 344 pair heats, loses setting control and smears the roller-rib contact.
- The 320 series at 40 mm bore (80×21 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.
- When the outer ring rotates, reverse the fit logic and provide cup location; the tapered contact of 344 pushes the rings apart under load, so a non-located cup walks its seat even when the shaft is fixed.
- 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 344 mounting error.
- Catalogue reference speed and limiting speed are different limits: the 7,000 r/min reference is a thermal criterion under load, while the 8,500 r/min limiting value is the mechanical ceiling — observe both.
- The 87.6/80 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 344 (basic, B steeper angle, Q/J2 clearance variants); they are not interchangeable order numbers — quote the full SKF 344/332 AA designation when purchasing and match the execution to the mounting arrangement.
Frequently asked questions
Can a single 344 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 344 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 344 position and vice versa — verify load direction, Fa/Fr ratio and speed before substituting.
What shaft and housing fits suit 344?
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 21 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 344 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 344?
The SKF 344/332 AA is a single-row tapered roller bearing with 40 mm bore, 80 mm outer diameter and 21 mm width (1.575 × 3.15 × 0.827 in). From SKF catalogue PUB BU/P1 17000: basic dynamic load rating C 87.6 kN, C0 80 kN, fatigue load limit Pu 9.15 kN, reference speed 7,000 r/min, limiting speed 8,500 r/min, mass about 470 g. It is an open, separable bearing with a pressed-steel cage.
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.