51109-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 51109-SKF model number is decoded

51109 is SKF's 45 mm-bore single-direction thrust ball bearing in the 51100 series to the ISO 104 dimension plan, with a flat housing seating surface, measuring 45×65×14 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 09 encode the bore as 45 mm (code 09 × 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 45×65×14 mm (1.772×2.559×0.551 in), 10.0 mm radial section, C 26.5 kN, C0 69.5 kN, Pu 2.55 kN. reference speed 4,500 r/min (thermal) and limiting speed 6,300 r/min (mechanical), catalogue mass 140 g. Minimum-load arithmetic: with dm ≈ 55.0 mm and factor A 0.025, Fam ≈ A·(n·dm/1000)² at the 4,500 r/min reference speed is about 1.5 kN for 51109; below that preload the balls skid and smear the tracks. Load balance: C0 69.5 kN against C 26.5 kN gives a 2.62 ratio — thrust ball bearings are chosen on static rating and F_a/C0 far more often than on L10 life, while Pu 2.55 kN enters the adjusted-life check. Bore-to-OD planning: OD 65 over bore 45 is a 1.44× step for this size, and the 14 mm height gives a bore/height ratio of 3.21; use these ratios when the housing recess around the 45 mm shaft is the first constraint. Light-load floor: Pu = 2.55 kN is the equivalent-load threshold below which the SKF adjusted-life equation credits very long life for 51109; the number is 10 % of the 26.5 kN dynamic rating. Static-first selection data: 69.5 kN C0 spread across the 14 mm stack gives 5.0 kN of static rating per height millimetre, and the 140 g mass/C0 ratio is about 2 g per static kN — crane-hook and screw positions are normally sized on these two figures. 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 45 mm size the pressed cage and separable washers make the bearing interchangeable across brands on the ISO 104 plan, but the SKF ratings 26.5/69.5 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

• The third digit grades the section: 511 light, then 512, 513 and 514 progressively taller and heavier at the same bore — select from 26.5/69.5 kN and the available 65 mm OD, never substitute a lighter series for a heavier one without rechecking C and C0.
• 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 26.5 kN track before first rotation.
• The three components are separable and interchangeable within the ISO 104 size, but keep this bearing's parts together in service and never combine washers from different manufacturers or a worn washer with a new ball set.
• Keep the applied thrust above Fam ≈ A·(n·dm/1000)² with the printed factor A 0.025; for 51109 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.
• Ordering discipline for 51109: the catalogue page quotes 51109 and its 26.5/69.5 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.