30305 bearing: complete specifications & equivalents

Specification table

Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.1 metric single-row TRB) · extracted 2026-09-26

Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.1 metric 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.

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 30305 model number is decoded

30305 is a single-row tapered roller bearing in the ISO 30300 dimension 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.On the SKF nameplate, 30305 follows the ISO 355 convention: 3 for the tapered-roller type, 03 for the heavy-OD section, final digits 05 for the 25 mm bore. The SKF catalogue adds the ISO 355 dimension-series code after the bare number (e.g. 2FB); it is the dimensional series, not a separate part number. At 9,500 r/min reference speed the 18.5 mm-section 30305 is governed thermally by preload and lubricant flow; grease or oil selection should be made against that value, with 12,000 r/min as the mechanical ceiling. Because the contact line is tapered, one 30305 reacts thrust in a single direction; bidirectional shafts need an O or X pair, and a rotating cone on a 25 mm shaft typically takes a k5 seat with an H7 housing bore.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• At a 25 mm bore the thin cone and cup are easily distorted by an over-tight shaft nut; check seat runout (target Ra ≤ 0.8 µm) and torque the locknut progressively — a pinched 30305 shows up as gearbox vibration long before it fails.
• The 303 series at 25 mm bore (62×18.25 mm) carries a larger OD and higher capacity than 30205 at the same bore; the bigger section runs hotter, so re-check the 12,000 r/min speed ceiling and shoulder diameters before substituting.
• When the outer ring rotates, reverse the fit logic and provide cup location; the tapered contact of 30305 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 30305 mounting error.
• The 30305 shares its ISO 355 envelope with other tapered bearings of the same code but is not a drop-in replacement for a ball bearing: it cannot run effectively under pure radial load without a minimum axial load, and a deep-groove bearing cannot replace its combined-load duty.
• The 55.3/43 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 30305 (basic, B steeper angle, Q/J2 clearance variants); they are not interchangeable order numbers — quote the full SKF 30305 designation when purchasing and match the execution to the mounting arrangement.