Koyo NJ311 Cylindrical Roller Bearing, 55 x 120 x 29 mm

This Koyo single-row cylindrical roller bearing has linear contact between the rollers and raceway, which gives it high radial load capacity. It suits heavy radial loads and impact loads, and because it can be machined very accurately it also suits high-speed applications. The inner ring or outer ring is separable, so mounting and dismounting are easy. The NJ type carries axial load in one direction as well as radial load. This page covers the Koyo NJ Cylindrical Roller Bearing, 300 Series, available in 10 bore diameter x outer diameter x width (mm) options: 20 x 52 x 15, 25 x 62 x 17, 30 x 72 x 19, 35 x 80 x 21, 50 x 110 x 27, 55 x 120 x 29, 60 x 130 x 31, 65 x 140 x 33 and 2 more.

The range has 10 sizes from 20 to 75 mm bore, in the 300 series. Boundary dimensions are to JIS B 1512 and tolerances to JIS B 1514-1. Load ratings and limiting speeds in the Koyo catalogue apply to the machined cage. Koyo bearings are made by JTEKT Corporation.

Where this product is used

• Large and medium size motors
• Traction motors and generators
• Internal combustion engines
• Gas turbines
• Machine tool spindles
• Speed reducers
• Cargo transport equipment

Features

• Linear roller contact: high radial load capacity for heavy radial and impact loads, and suited to high speeds
• NJ type: carries axial load in one direction as well as radial load
• Separable inner ring or outer ring, so mounting and dismounting are easy
• Pressed steel (//) or copper alloy machined (FY) cage depending on series and size
• Allowable misalignment 0.0006 rad (2') to 0.0009 rad (3') at normal load
• Basic dynamic load ratings 23.1 to 194 kN and static 19.2 to 205 kN depending on size
• Boundary dimensions to JIS B 1512, tolerances to JIS B 1514-1

Key specifications

Available sizes

Selecting the right option

Select by bore d first, then check the outside diameter D and width B in the table against your housing.

The ratings and limiting speeds shown are the Koyo catalogue values for the machined cage. Bearings with a pressed cage may have different values, so consult JTEKT or AIMS Industrial for pressed cage bearings.

Dynamic equivalent radial load is Pr = Fr and static equivalent radial load is P0r = Fr.

Choose the type by how the bearing is located: NU and N types are free side bearings, NJ and NF types take axial load in one direction, and NUP types take a certain degree of axial load in both directions. Axial load must stay within the allowable axial load for the size, so check it before selecting a type.

Fitting and use

Mounting dimensions in the variant specification (da, db, dc, dd, Da, Db, ra, rb) are listed as in the Koyo catalogue row for the size. Which shoulders apply depends on the bearing type, so check the catalogue figure for the type before machining the shaft and housing.

Fw is the roller set bore diameter of NU, NJ and NUP types, and Ew is the roller set outside diameter of N and NF types. Both are needed when matching an inner ring or outer ring assembly to its mating ring.

Allowable misalignment is about 0.0006 rad (2') to 0.0009 rad (3') when Pr/Cr is about 10%, and 0.0012 rad (4') when Pr/Cr is about 6%. Consult JTEKT if a larger allowance is needed.

Related products

Also available from Koyo: the NU 300 series range, the NUP 300 series range, the N 300 series range and the NF 300 series range.