BA-7 bearing: complete specifications & equivalents

Specification table

Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018)) · extracted 2026-09-28

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 BA-7 model number is decoded

BA 7 is SKF's BA-series miniature single-direction thrust ball bearing for a 7 mm shaft — the BA digits give bore in millimetres directly — supplied as a shaft washer, a housing washer and a stamped sheet-steel ball-cage assembly, 7×17×6 mm. The separable set comprises a shaft washer (ground bore, tight fit on the shaft), a loose-bore housing washer and one ball-cage assembly, reacting axial force in one direction and carrying no radial load. the BA prefix marks SKF miniature thrust ball bearings for shaft diameters below 10 mm — the digits give the bore in millimetres directly, so a BA 7 fits a 7 mm shaft rather than using the two-digit bore code. BA miniatures use the standard stamped sheet-steel ball-cage assembly: two pressed steel washers retain a small ball complement, and at these dimensions the cage and washers are handled as three loose parts. Envelope 7×17×6 mm (0.276×0.669×0.236 in), 5.0 mm radial section, C 2.51 kN, C0 2.9 kN, Pu 0.108 kN. reference speed 14,000 r/min (thermal) and limiting speed 19,000 r/min (mechanical), catalogue mass 6 g. Envelope economics: the 6 mm axial height over a 5.0 mm radial section yields 0.4 kN of dynamic capacity per height millimetre, and the bearing weighs 6 g for 2.51 kN C — about 2 g per rated kN. Section proportions: the 5.0 mm radial section compares with 7 mm of bore (section/bore ≈ 0.71) and the 6 mm height is 1.20× that section — the proportions that identify the BA envelope at a glance. Bore-to-OD planning: OD 17 over bore 7 is a 2.43× step for this size, and the 6 mm height gives a bore/height ratio of 1.17; use these ratios when the housing recess around the 7 mm shaft is the first constraint. Rating split for documentation: dynamic 2.51 kN (L10 life), static 2.9 kN (safety factor s0), fatigue limit 0.108 kN (adjusted life) — three different uses of three different numbers for BA 7, none interchangeable with another. Imperial cross-check for procurement drawings: 0.276 in bore, 0.669 in OD, 0.236 in height, and the 6 g catalogue mass converts to 0.006 kg (0.2 oz). Miniature handling note: the three BA components — shaft washer, housing washer and ball-cage assembly — are supplied loose and separate on contact, so mount the unit inside its housing recess before the shaft is offered; a dropped BA set scatters washers and balls that are nearly impossible to sort by eye, and a washer fitted reversed cannot be seen from outside once the cover is on. For reference, the 7×17 mm outline occupies less than a pencil eraser yet still publishes C0 2.9 kN; select the housing recess before the screw length, because the 6 mm stack plus cover is often the tallest feature of a miniature axial stop.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• Keep the applied thrust above Fam ≈ A·(n·dm/1000)² with the printed factor A 4.40×10^-5; for BA 7 a spring preload or the rotor weight is part of the selection at light load and high speed, because unloaded balls skid rather than roll.
• Identify the washers before fitting: the shaft washer has the ground, smaller bore and takes an interference fit on the 7 mm shaft, while the housing washer bore is larger and runs loose; swapping them locks the ball set and burns the tracks.
• Heat the shaft washer to at most 120 °C for mounting, or press it via a sleeve on its ground bore — force applied through the housing washer or the ball set brinells the 2.51 kN track before first rotation.
• The BA 7 is a pure axial bearing: it must never be subjected to radial load — any radial force on the 7 mm shaft has to be carried by a radial bearing mounted alongside it.
• There is no 51xxx coded size below 10 mm bore: the BA range is the miniature entry point for pure axial location, and at 7 mm the limit loads are small enough that shaft and housing squareness, not capacity, usually governs the design.
• Ordering discipline for BA 7: the catalogue page quotes BA 7 and its 2.51/2.9 kN ratings as one exact article; bare-number substitutions from another series or brand need a fresh dimension and rating check, not a like-for-like assumption.