53308 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 53308 model number is decoded

53308 is SKF's 40 mm-bore single-direction thrust ball bearing in the 53300 series to the ISO 104 dimension plan, with a sphered housing washer paired to a U seat washer, measuring 40×78×28.5 mm U 308 seat washer companion included in the mounted H1 dimension. 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. in the 53xxx designation the 3 marks a single-direction bearing whose housing washer has a sphered (convex) seating surface, intended to run against the matching U seat washer; the third digit 2–4 grades the section. the final two digits 08 encode the bore as 40 mm (code 08 × 5), the standard SKF bore-code rule shared with radial bearings. with no cage suffix this is the standard execution with a stamped sheet-steel ball-cage assembly (pressed cage) — the light, quiet and economical cage for small and medium thrust-ball sizes. Envelope 40×78×28.5 mm (1.575×3.071×1.122 in), 19.0 mm radial section, C 61.8 kN, C0 122 kN, Pu 4.5 kN. Mounted height H1 31 mm includes the U 308 seat washer; the bearing alone is 28.5 mm high. reference speed 2,800 r/min (thermal) and limiting speed 4,000 r/min (mechanical), catalogue mass 670 g. Envelope economics: the 28.5 mm axial height over a 19.0 mm radial section yields 2.2 kN of dynamic capacity per height millimetre, and the bearing weighs 670 g for 61.8 kN C — about 11 g per rated kN. Stack/annulus proportions: the 28.5 mm axial stack over the 3,522 mm² washer annulus gives 8.09 mm of height per annular square millimetre ×10⁻³, and at 670 g the bearing holds about 182.1 kN of C0 per kilogram. Load balance: C0 122 kN against C 61.8 kN gives a 1.97 ratio — thrust ball bearings are chosen on static rating and F_a/C0 far more often than on L10 life, while Pu 4.5 kN enters the adjusted-life check. Capacity density: 61.8 kN C from 0.670 kg of bearing steel gives about 92.2 kN per kilogram; static density is correspondingly 182.1 kN/kg at C0 122 kN. Preload at the mechanical ceiling: repeating Fam ≈ A·(n·dm/1000)² with factor A 0.077 at the 4,000 r/min limiting speed raises the required axial preload to about 4.3 kN; the reference-speed value 2.1 kN is the thermal design point. Sphered-seating order-number note: the convex back face of the housing washer is finish-ground spherical and is delivered to mate with the separately ordered U seat washer, which presents a flat face to the housing and a concave face to the washer; together they accommodate initial static misalignment, but the pair must be kept clean, greased at the spherical interface and never replaced by a washer-on-flat-steel makeshift. The aligning angle is set by how far the sphered back of the 78 mm washer can tilt inside the U 308 seat; check the actual tilt allowance in the mounting drawing, since the 2.5 mm washer thickness step does not by itself quantify it.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• Minimum axial load still applies with factor A 0.077: a self-aligning seat does not prevent ball skidding, so provide spring preload or sufficient rotor weight at light load and speed.
• The self-aligning feature is checked at commissioning by hand: with the shaft under no load the assembly must swivel and settle; a stiff spherical seat means dirt, a mismatched U washer, or a register bored off-axis.
• The spherical seat accommodates INITIAL static misalignment between shaft and housing; it is not a swivel for continuous oscillation, and the bearing still carries pure axial load with no radial capacity.
• Keep the sphered interface clean and lightly greased: scale, paint or grit between the washer back and U 308 locks the aligning function and frets under load; re-grease the contact at every overhaul.
• The 61.8/122 kN figures belong to 53308 specifically (the single sphered pressed steel execution of 53308); suffixed, sphered and counterpart-series order numbers are separate articles, and U 308 is ordered separately, so write the complete designation on the order and the maintenance record.