NACHI5209Double Row Angular Contact Ball Bearing 45x85x30.2 mm, Open Both Faces, 30° Contact Angle, 3209 Envelope

Product Description

What this part is

A Nachi 5209 double-row angular contact ball bearing — 45 mm bore, 85 mm outside diameter, 30.2 mm (1-3/16 in) width, open on both faces. Two rows of balls run on opposed angled raceways inside a single pair of rings, so one bearing carries radial load and thrust in both directions and also resists shaft tilting. It is the standard part where a shaft has to be located axially and supported radially without room for two separate bearings.

Decoding the designation

5209 – Nachi double-row angular contact ball bearing, 45 mm bore; the same envelope as the ISO 3209 designation
Nominal contact angle for the double-row 3200 / 5200 family: 30°
No closure suffix, so both faces are open
No clearance suffix, so internal clearance is normal (CN)

What these specs mean in practice

Two opposed rows inside one bearing give thrust capacity in both directions, which is what lets this part replace a back-to-back pair of single-row bearings and shorten an assembly. The wide effective contact span between the two rows also resists moment loading, so an overhung pulley or fan wheel tilts the shaft less. The 30.2 mm width is the double-row width: a 6209 deep groove bearing in the same 45 x 85 mm envelope is 19 mm wide and carries far less thrust, and it is not a substitute. With both faces open, the housing supplies and retains the lubricant.

Published specifications

Bore: 45 mm (1.7717 in)
Outside diameter: 85 mm (3.3465 in)
Width: 30.2 mm (1-3/16 in)
Rows: 2
Contact angle: 30° nominal
Rolling elements: balls
Closure: open both faces
Internal clearance: CN (normal)
Thrust capability: both directions
Material: through-hardened bearing steel

Quantity and configuration

Sold as 1 Pc. One complete double-row bearing, open on both faces. No seal, shield, snap ring, spacer or lock nut is included.

Fitting notes

Mounting force is applied to the ring being fitted so that no load passes through the balls. Because the bearing locates the shaft in both axial directions, it is clamped in the housing between a shoulder and an end cap, and the second bearing on the shaft is left free to float. The open faces take lubricant from the housing cavity, packed to roughly one third of its free volume for grease service.

Interchange guidance

The direct equivalent is an open double-row angular contact ball bearing in the 45 x 85 x 30.2 mm envelope: SKF 3209 A, FAG 3209-B-TVH, NSK 3209B, MRC 5209. Shielded and sealed versions such as 3209-2Z, 5209-2RS and MRC 5209MFF share the envelope but differ in closure and running friction, so those are related versions rather than drop-in equivalents. A 6209 single-row deep groove bearing is not an interchange.