NACHI 7311B Angular Contact Ball Bearing, 40°, 55x120x29 mm

This NACHI range covers 26 single row angular contact ball bearings with a 40° contact angle (B) and a pressed steel cage, from 12 to 85 mm bore (outer diameters 32 to 160 mm, widths 10 to 37 mm): 17 in the 72 series and 9 in the 73 series. Select the size from the drop-down: each size has its own bearing number, load ratings and limiting speeds in the Model Details.

A single row angular contact ball bearing has a set contact angle in both rings, so it carries radial, axial or combined load, with any axial load in one direction only. Compared with the 30° design the 40° angle carries more axial load, with lower speed and lower radial load capability. Single bearings are generally used in pairs, and DB or DF sets carry axial load in both directions.

Where this product is used

• Gearboxes and speed reducers that carry combined radial and axial load
• Pumps and compressors
• General industrial machinery with a defined axial load direction
• Back-to-back, face-to-face or tandem paired arrangements

Features

• 40° contact angle (B): compared with the 30° design, greater axial load capacity with lower speed and radial load capability; axial load in one direction only
• Pressed steel cage, the standard cage for these bearing numbers; the limiting speeds shown include the 0.8 factor for pressed cages
• Single bearings, generally used in pairs: back-to-back (DB) or face-to-face (DF) sets carry axial load in both directions
• Open design with no seals or shields
• Basic dynamic load rating 7.2 to 128 kN across the range

Key specifications

Available sizes

Selecting the right option

Contact angle. This range is the 40° (B) design. Compared with the 30° design it carries more axial load, with lower speed and lower radial load capability. For higher speed with less axial load the 15° (C) range in Related products is the alternative.

Series. The 72 series is the lighter section and the 73 series the heavier section for the same bore, so check the outer diameter and width against the housing. Ratings and mass in the tables are for one bearing.

Single bearings are generally used in pairs to take the axial force that the radial load induces: DB or DF sets carry axial load in both directions, and a DT set carries it in one direction.

Fitting and use

Check the load and speed against the figures in the table before ordering, and apply a suitable safety factor. Limiting speeds apply to lightly loaded bearings with high quality grease or oil in proper quantity.

For a single bearing or a tandem (DT) pair at 40°, the dynamic equivalent radial load is P = Fr when Fa/Fr is 1.14 or less, and P = 0.35 Fr + 0.57 Fa above that. The static equivalent load is Por = 0.5 Fr + 0.26 Fa, and if that is less than Fr use Por = Fr.

The speeds in this listing are the catalogue table values multiplied by 0.8, the factor for the pressed steel cage that is standard on these bearing numbers. Matched DB, DF or DT sets are made up with pre-adjusted clearance, so ask AIMS if you need a set rather than two single bearings.

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.

Related products

Two more 40° sizes are on their own pages: NACHI 7200B (10 x 30 x 9 mm) and NACHI 7313B (65 x 140 x 33 mm). The 15° (C) flush-ground single row range, for higher speed: NACHI 15° single row angular contact ball bearings (28 sizes). For one unit that carries axial load in both directions, see the double row range: open (20 sizes), ZZ shielded 25 to 70 mm bore (12 sizes), ZZ shielded 10 to 40 mm bore (6 sizes) and 2NS sealed (8 sizes).