RNA4840 bearing: complete specifications & equivalents

Specification table

Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.3 machined rings with flanges, without an inner ring) · extracted 2026-09-26

Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.3 machined rings with flanges, without an inner ring); 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 RNA4840 model number is decoded

RNA 4840 belongs to the machined-ring needle roller family: an outer ring turned and ground to 250 mm with two retaining flanges, a roller-and-cage set inside, and envelope 220×250×50 mm on a hardened 220 mm shaft. Reading the designation: RNA gives the series and the numbers the boundary plan — 220 mm Fw for the shaft seat, 50 mm width; the 250 mm OD comes from the dimension series, and the absence of an inner ring is built into the family name. The machined ring is through-hardened and ground on OD, bore-side raceway and faces; the flanged lip design means the housing shoulder can be omitted — the ring clamps axially between housing wall and cover washer. Catalogue mass 3350 g at 220×250×50 mm makes this one of the highest capacity-per-gram choices in the dimension series 48 needle roller bearings without inner ring; the limit is usually the shaft's ability to serve as a raceway, not the rolling contact itself. Fit the outer ring with a press and a fitting sleeve, not by hammering the flanges — rolled flanges chip; the 250 mm ground OD takes the press fit that prevents outer-ring creep in oscillating duty.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• Above 50 mm bore, thermal growth matters: the 220 mm inner ring or journal grows with temperature faster than the housing, and the small clearance of a needle roller contact leaves little reserve — check running clearance hot, not just at assembly.
• Reference and limiting speeds are different limits: the 1,800 r/min reference is the thermal criterion under load, The limiting value is mechanical; the reference value is thermal under load, and grease choice moves it substantially.
• Hardness is load capacity: in families without an inner ring the 220 mm journal must hold 58–64 HRC with a ground finish; a surface that looks fine but sits at 45 HRC will rib the raceway within weeks.
• The 224/735 kN ratings and 3350 g mass are SKF catalogue values transcribed from ch. 7.3 of PUB BU/P1 17000 (PDF table page 636); combined-type axial ratings appear in the text above because the structured record carries radial values only.