51234-M 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 51234-M model number is decoded

51234 M is SKF's 170 mm-bore single-direction thrust ball bearing in the 51200 series to the ISO 104 dimension plan, with a flat housing seating surface, measuring 170×240×55 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 34 encode the bore as 170 mm (code 34 × 5), the standard SKF bore-code rule shared with radial bearings. suffix M identifies a one-piece machined brass cage, ball-centred: the large-size and heavy-section option for higher speeds, shock loads and thin-film lubrication where a pressed cage would distort. Envelope 170×240×55 mm (6.693×9.449×2.165 in), 35.0 mm radial section, C 270 kN, C0 930 kN, Pu 24 kN. reference speed 1,200 r/min (thermal) and limiting speed 1,700 r/min (mechanical), catalogue mass 8150 g. Preload at the mechanical ceiling: repeating Fam ≈ A·(n·dm/1000)² with factor A 5.4 at the 1,700 r/min limiting speed raises the required axial preload to about 655.8 kN; the reference-speed value 326.8 kN is the thermal design point. Section proportions: the 35.0 mm radial section compares with 170 mm of bore (section/bore ≈ 0.21) and the 55 mm height is 1.57× that section — the proportions that identify the 51200 envelope at a glance. Mass and section check: 8150 g inside the 170×240×55 mm outline leaves a 35.0 mm radial section, and the 930 kN static rating is 3.44× the dynamic rating — plan static safety and minimum preload against those figures. Capacity density: 270 kN C from 8.150 kg of bearing steel gives about 33.1 kN per kilogram; static density is correspondingly 114.1 kN/kg at C0 930 kN. Track-circle loading: per millimetre of mean track circumference the 270 kN dynamic rating corresponds to roughly 0.42 kN/mm of π·dm track, a useful comparison against the other dimension series of the 170 mm bore. Machined-cage order-number note: the M brass cage is a one-piece ball-centred window cage, chosen at the heavy end of the section for speed and shock duty; it is heavier and stiffer than the pressed-steel execution of the smaller sizes and tolerates interrupted lubrication far better, which is why the catalogue restricts the M suffix to the large bores. At 8150 g the machined brass cage represents a meaningful fraction of total mass; balancing checks on high-speed 170 mm vertical shafts should use the actual M-execution weight, not the lighter pressed-cage catalogue value.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• When the housing seat cannot be machined square to the 170 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 170 mm shaft, while the housing washer bore is larger and runs loose; swapping them locks the ball set and burns the tracks.
• 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 270 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 55 mm stack; thrust-ball bearings on horizontal shafts should have the shaft washer (the tight one) against the rotating element.
• Ordering discipline for 51234: the catalogue page quotes 51234 M and its 270/930 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.