51206-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 51206-SKF model number is decoded

51206 is SKF's 30 mm-bore single-direction thrust ball bearing in the 51200 series to the ISO 104 dimension plan, with a flat housing seating surface, measuring 30×52×16 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 06 encode the bore as 30 mm (code 06 × 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 30×52×16 mm (1.181×2.047×0.63 in), 11.0 mm radial section, C 25.1 kN, C0 51 kN, Pu 1.86 kN. reference speed 4,800 r/min (thermal) and limiting speed 6,700 r/min (mechanical), catalogue mass 130 g. Mass and section check: 130 g inside the 30×52×16 mm outline leaves a 11.0 mm radial section, and the 51 kN static rating is 2.03× the dynamic rating — plan static safety and minimum preload against those figures. Minimum-load arithmetic: with dm ≈ 41.0 mm and factor A 0.013, Fam ≈ A·(n·dm/1000)² at the 4,800 r/min reference speed is about 503 N for 51206; below that preload the balls skid and smear the tracks. Speed-ratio note for this exact unit: the reference speed is 4,800 r/min against a 6,700 r/min limiting speed, a reference-to-limit ratio of 0.72. Capacity density: 25.1 kN C from 0.130 kg of bearing steel gives about 193.1 kN per kilogram; static density is correspondingly 392.3 kN/kg at C0 51 kN. Section proportions: the 11.0 mm radial section compares with 30 mm of bore (section/bore ≈ 0.37) and the 16 mm height is 1.45× that section — the proportions that identify the 51200 envelope at a glance. 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 30 mm size the pressed cage and separable washers make the bearing interchangeable across brands on the ISO 104 plan, but the SKF ratings 25.1/51 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 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.
• When the housing seat cannot be machined square to the 30 mm shaft, the sphered 53-series execution of this size with its U seat washer is the self-aligning counterpart of this flat 51200 bearing.
• Identify the washers before fitting: the shaft washer has the ground, smaller bore and takes an interference fit on the 30 mm shaft, while the housing washer bore is larger and runs loose; swapping them locks the ball set and burns the tracks.
• Keep the applied thrust above Fam ≈ A·(n·dm/1000)² with the printed factor A 0.013; for 51206 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.
• The 25.1/51 kN figures belong to 51206 specifically (the single flat pressed steel execution of 51206); suffixed, sphered and counterpart-series order numbers are separate articles, so write the complete designation on the order and the maintenance record.