51108-SKF 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 51108-SKF model number is decoded

51108 is SKF's 40 mm-bore single-direction thrust ball bearing in the 51100 series to the ISO 104 dimension plan, with a flat housing seating surface, measuring 40×60×13 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. in the 51xxx designation the first 1 marks a single-direction bearing with a flat housing seating surface; the third digit 1–4 grades the dimension series from the light 511 section through the heavy 514 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 40×60×13 mm (1.575×2.362×0.512 in), 10.0 mm radial section, C 25.5 kN, C0 63 kN, Pu 2.32 kN. reference speed 5,000 r/min (thermal) and limiting speed 7,000 r/min (mechanical), catalogue mass 120 g. Static-first selection data: 63 kN C0 spread across the 13 mm stack gives 4.8 kN of static rating per height millimetre, and the 120 g mass/C0 ratio is about 2 g per static kN — crane-hook and screw positions are normally sized on these two figures. Capacity density: 25.5 kN C from 0.120 kg of bearing steel gives about 212.5 kN per kilogram; static density is correspondingly 525.0 kN/kg at C0 63 kN. Washer-annulus check: the π/4·(D²−d²) contact annulus of 51108 covers about 1,571 mm², distributing C0 63 kN over a mean track circle of π·dm ≈ 157 mm. Sizing arithmetic on the 40 mm bore: 25.5 kN C over the 10.0 mm radial section gives 2.5 kN per section millimetre, and the 13 mm stack height is 1.30× that section — proportions typical of a 51100 thrust section. Imperial cross-check for procurement drawings: 1.575 in bore, 2.362 in OD, 0.512 in height, and the 120 g catalogue mass converts to 0.120 kg (4.2 oz). Execution note for this order number: the flat housing seating surface must be machined square to the shaft axis and supported across the full washer face — unlike the sphered 53-series execution this pressed-cage 51-series bearing has no self-aligning capability at all, so seat squareness is checked at mounting, not compensated in service. On this 40 mm size the pressed cage and separable washers make the bearing interchangeable across brands on the ISO 104 plan, but the SKF ratings 25.5/63 kN are this catalogue's figures — confirm the replacement order's ratings rather than swapping on envelope alone.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• 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 25.5 kN track before first rotation.
• On vertical shafts retain the loose housing washer positively with a cover or ring and verify the grease fill does not drain out of the 13 mm stack; thrust-ball bearings on horizontal shafts should have the shaft washer (the tight one) against the rotating element.
• Identify the washers before fitting: the shaft washer has the ground, smaller bore and takes an interference fit on the 40 mm shaft, while the housing washer bore is larger and runs loose; swapping them locks the ball set and burns the tracks.
• A 51-series bearing reacts thrust in one direction only — reversing positions need a mirrored single-direction pair or a 52-series double-direction unit; fitting a single 51108 against two-way load lifts the loose washer off its raceway.
• The 25.5/63 kN figures belong to 51108 specifically (the single flat pressed steel execution of 51108); suffixed, sphered and counterpart-series order numbers are separate articles, so write the complete designation on the order and the maintenance record.