NACHI double shielded, 25 x 52 x 20.6mm

This NACHI range covers 12 double row angular contact ball bearings with two metal shields (ZZ), from 25 to 70mm bore (outer diameters 52 to 125mm, widths 20.6 to 49.2mm): 8 in the 52 series and 4 in the 53 series. Select the size from the drop-down: each size has its own bearing number, with load ratings and limiting speeds for the sizes where they are published in the Model Details.

A double row angular contact ball bearing is built like two single row bearings mounted back-to-back in one unit. It carries radial load, moment load and axial load in both directions, but because fewer balls fit in each row it has less load capacity than an equivalent back-to-back pair of single row bearings. The contact angle is 20° (no letter in the bearing number) and the cage is pressed steel.

Where this product is used

• Pumps and compressors
• Gearboxes and speed reducers
• Shaft positions that need radial, moment and bidirectional axial load support from one bearing
• General industrial machinery

Features

• Two metal shields (ZZ) close both sides of the bearing
• Two rows of balls at a 20° contact angle carry radial, moment and axial load in both directions
• Pressed steel cage
• Basic dynamic load rating 21.8 to 86 kN across the range

Key specifications

Available sizes

Fitting and use

Check the load and speed against the figures in the specifications before ordering, and apply a suitable safety factor. Limiting speeds apply to lightly loaded bearings that are properly lubricated.

For a 20° double row bearing, the dynamic equivalent radial load is P = Fr + 1.09 Fa when Fa/Fr is 0.57 or less, and P = 0.70 Fr + 1.63 Fa above that. The static equivalent load is Por = Fr + 0.84 Fa.

When fitting, apply force only through the ring that is being pressed on (the inner ring on a shaft, the outer ring in a housing), never through the other ring or the balls.

Choosing the right option

Single or double row. A double row bearing takes radial, moment and bidirectional axial load in one housing position.

Contact angle. These bearings have a 20° contact angle (no letter in the bearing number).

Shielded or open. From the 5206 size up, the shielded type has lower load ratings than the open bearing of the same number and is rated for grease lubrication only. For sizes 5200 to 5205 the ratings are the same for all closure types.

More sizes with the same closure are on: NACHI double row angular contact bearings, ZZ shielded, 10 to 40mm bore (6 sizes).

Double row bearings with other closures: open (20 sizes), 2NS sealed (8 sizes).

For separate single row bearings used in pairs, see: 15° flush-ground (28 sizes), 40° (26 sizes).