RNA4918 bearing: complete specifications & equivalents
The RNA4918 is a ISO 1206 radial bearing sized 105 x 125 x 35 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 105 mm |
| Outer diameter D | 125 mm |
| Width B | 35 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | none |
| Basic dynamic load rating C | 112 kN |
| Basic static load rating C0 | 265 kN |
| Fatigue load limit Pu | 32.5 kN |
| Reference speed (thermal) | 3800 rpm |
| Limiting speed (mechanical) | 4300 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 750 g |
| Manufacturer designation | RNA 4918 |
| Standard | ISO 1206 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.3 machined rings with flanges, without an inner ring |
| Last verified | 2026-09-26 |
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.
Dimensions in inches & RNA-49-series range
| Bore d | 4.134 in |
|---|---|
| Outer diameter D | 4.921 in |
| Width B | 1.378 in |
| ISO bore code | 18 |
| Radial section height (D−d)/2 | 10 mm |
| Smallest bore in RNA-49-series | 14 mm |
| Largest outer diameter in RNA-49-series | 190 mm |
| Width range across RNA-49-series | 13–50 mm |
| Bore position in RNA-49-series (smallest first) | 22 of 28 |
| Bore above smallest RNA-49-series size | 91 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the RNA4918 model number is decoded
RNA 4918 is a ribbed machined-ring needle roller bearing (no inner ring) sized 105×125×35 mm: the ground outside diameter seats in the housing, the integral flanges hold the rollers, and the 105 mm shaft journal completes the bearing. In SKF nomenclature RNA families drop the inner ring: the numbers after the letters give the 105 mm under-roller diameter and the 35 mm width, with the 125 mm outside diameter set by the dimension series 49 needle roller bearings without inner ring plan. 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 750 g at 105×125×35 mm makes this one of the highest capacity-per-gram choices in the dimension series 49 needle roller bearings without inner ring; the limit is usually the shaft's ability to serve as a raceway, not the rolling contact itself. Grease through the housing groove before fitting the shaft; the integral flanges hold the grease film at the roller ends, which is where these bearings first starve.
Typical equipment & failure modes
Common applications
- cam followers built up from separate components
- crank pins and eccentrics where the hardened journal is the raceway
- gearbox planetary and idler gears on hardened pins
- piston-pin style pivots in hydraulic pumps
Known failure patterns
- needle edge loading and raceway denting when the shaft deflects beyond the compensation range
- cage pocket wear and roller skew after sustained operation with too little radial preload
- abrasive paste formation from dust ingressing past open ends without effective housing seals
- electrical erosion on VFD-driven shafts without brush or insulated mounting
- smearing of rollers and journal during idle periods because the radial section holds too little lubricant
Selection pitfalls — read before you substitute
- Above 50 mm bore, thermal growth matters: the 105 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 3,800 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 105 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 112/265 kN ratings and 750 g mass are SKF catalogue values transcribed from ch. 7.3 of PUB BU/P1 17000 (PDF table page 634); combined-type axial ratings appear in the text above because the structured record carries radial values only.
Frequently asked questions
What mounting mistakes ruin a RNA 4918?
Press on the ring faces only with a fitting sleeve, keep everything square to the 105 mm seat, and never transmit force through the rolling elements. Follow the catalogue's seat tolerances — the narrow needle contact forgives neither tilt nor burrs.
Is the RNA 4918 sealed?
No — this execution is open and depends on the housing sealing arrangement; grease it at assembly and keep the relubrication interval short in dirty duty.
Which dimensions does the RNA 4918 have?
A RNA 4918 measures 105 mm bore/Fw × 125 mm outside diameter × 35 mm width (4.134 × 4.921 × 1.378 in). From SKF catalogue PUB BU/P1 17000: radial dynamic rating C 112 kN, static C0 265 kN, fatigue limit Pu 32.5 kN, limiting speed 4,300 r/min, reference speed 3,800 r/min, mass about 750 g.
What does RNA 4918 mean in SKF part numbering?
RNA names a machined-ring needle roller bearing without inner ring: the figures give Fw 105 mm and width 35 mm, OD 125 mm comes from the dimension series, and the flanged outer ring retains the caged rollers.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.3 machined rings with flanges, without an inner ring on 2026-09-26. Read our editorial & correction policy.