7308-BECBM bearing: complete specifications & equivalents

Specification table

Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018)) · extracted 2026-09-27

Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018)); 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.

Cross references & equivalents

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 7308-BECBM model number is decoded

7308 BECBM is SKF's 40 mm-bore single-row angular-contact ball bearing in the 7300 series, nominal 40° (B) contact angle, 40×90×23 mm to the ISO dimension plan. 40° contact angle (suffix B): the steep standard single-row angle, giving the highest axial capacity at the cost of speed, with a recommended load ratio Fa/Fr ≥ 1. E marks the optimized internal design with an enhanced ball complement and race geometry. machined brass cage, ball-centred (suffix M), the choice for high speed, marginal lubrication and shock duty. CB means universally matchable with Normal axial internal clearance: the two side faces are ground so any two units form DB (back-to-back), DF (face-to-face) or DT (tandem) sets without regrinding. Envelope 40×90×23 mm (1.575×3.543×0.906 in), 25.0 mm radial section height, C 50 kN, C0 32.5 kN, Pu 1.37 kN.reference speed 9,500 r/min (thermal) and limiting speed 12,000 r/min (mechanical), catalogue mass 680 g. Load balance: C0 32.5 kN against C 50 kN gives a 0.65 ratio, typical of a steep-angle axial-oriented design; Pu 1.37 kN enters the SKF adjusted-life equation rather than the basic rating life. Sizing arithmetic on the 40 mm bore: 50 kN C divided by the 25.0 mm radial section height gives 2.0 kN per section millimetre; the 680 g mass and 3 % Pu/C share frame the light-load floor for the adjusted-life check. Bore-to-OD planning: OD 90 over bore 40 is a 2.25× step for this size, and the 23 mm width gives a bore/width ratio of 1.74; use these ratios when housing space around the 40 mm shaft is the first constraint. Cage detail specific to this order number: the M cage is a one-piece machined brass window cage centred on the balls, chosen for high speeds, thin-film lubrication and shock loads; it is heavier and stiffer than the stamped Y-cage execution and tolerates interrupted oil supply far better than the PA66 or PEEK alternatives. Do not substitute the stamped-brass BECBY order number expecting identical cage behaviour.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• One 7308-BECBM locates the shaft in one axial direction only; reversing-thrust positions need a DB or DF pair — or a double-row bearing — with preload set from the load diagram, never from assembly feel.
• Assign interference to the rotating ring — roughly k5 on a 40 mm rotating shaft with an H7 housing — and let the stationary ring slide for axial setting; reverse the logic if the outer ring rotates.
• Mount by induction-heating the inner ring to max 120 °C; driving the bearing home through the outer ring or balls brinells the asymmetric raceway.
• Keep the load ratio in the SKF design range: Fa/Fr ≥ 1 for this angle; below it the balls unload the contact ellipse and skid, which is why the catalogue insists on a minimum axial load (Fam ≈ A·(n·dm/1000)²) at high speed.
• The steep 40° angle of 7308-BECBM favours thrust-heavy combined loads; for a predominantly radial high-speed position the 25° ACCBM execution of the same size is the alternative order number.
• Universally matchable BECBM bearings arrive ready for set mounting, not preloaded sets: preload results from how the set is clamped, so follow the SKF stand-off-ring and nut-torque procedure.