Cylindrical Roller Bearings

· NU-type bearings have flanges on both sides of the outer ring and no flanges on the inner ring.

· N-type bearings have flanges on both sides of the inner ring and no flanges on the outer ring.

These designs allow limited bidirectional axial displacement of the shaft relative to the housing, accommodating length changes caused by thermal expansion. Thus, they are suitable as non-locating bearings.

· NJ-type cylindrical roller bearings have flanges on both sides of the outer ring and one flange on the inner ring.

· NF-type cylindrical roller bearings have flanges on both sides of the inner ring and one flange on the outer ring.

These provide unidirectional axial positioning of the shaft.

· NUP-type cylindrical roller bearings have flanges on both sides of the outer ring, one flange on the inner ring, and a loose flange on the other side. This enables bidirectional axial positioning of the shaft.

High-precision single-row cylindrical roller bearings with a 1:12 tapered bore for machine tool spindles are also produced.

Double-row cylindrical roller bearings are manufactured as precision-grade bearings for machine tool spindles and can also be used in other precision machinery.

· NN-type bearings have flanges on the inner ring and no flanges on the outer ring.

· NNU-type bearings have flanges on the outer ring and no flanges on the inner ring.

To facilitate the installation of lubrication devices, bearings with oil grooves and holes on the outer ring (suffix code W33) are primarily supplied. Products with either cylindrical or tapered bores are available based on customer requirements.

The basic dimensions of the bearings listed in the tables comply with ISO 15:1981.

Proper adjustment of the contact condition between the rollers and raceways not only prevents abnormal loading on the contact surfaces but also accommodates misalignment between the inner and outer rings caused by installation errors. The permitted tilt angles for cylindrical roller bearings are as follows:

· Narrow-type bearings (10, 2, 3, and 4 series): 3.5 arcminutes

· Wide-type bearings (22 and 23 series): 1.5 arcminutes

Larger tilt angles may be permissible depending on the load magnitude and required service life. Double-row cylindrical roller bearings do not permit any tilt angle.

Single-row cylindrical roller bearings are produced with tolerances up to P5 grade. Additionally, single-row and double-row cylindrical roller bearings with tapered bores for machine tool spindles are manufactured with P5 grade and higher tolerances, as well as special tolerance classes SP and UP.

Standard single-row cylindrical roller bearings are supplied with basic group clearance. Single-row bearings can also be provided with C3 group clearance, and some sizes are available with C4 group clearance. Double-row cylindrical roller bearings are supplied with C1 group clearance as standard. Bearings with cylindrical bores can also be supplied with C2 or C3 group clearance, while tapered bore bearings can be provided with C2 group clearance.

The standard cages for single-row cylindrical roller bearings are listed in the table below. Cages for NU, NJ, NF, and NUP-type bearings are typically the same as those for N-type bearings.

Bearings with glass fiber-reinforced nylon 66 cages (suffix code TN) are suitable for operating temperatures up to +120°C. For applications requiring continuous operation under high temperatures or harsh conditions, solid brass cages (suffix code M) are available. Bearings with standard designs using glass fiber-reinforced nylon 66 or brass cages can also be supplied with stamped steel cages upon customer request.

To prevent harmful sliding between the rollers and raceways due to centrifugal forces during high-speed operation, the minimum required load for the bearing can be estimated using the following formula:

F_r = K_r \cdot \left(6 + 4 \frac{n}{n_r}\right) \cdot \left( \frac{d_m}{100} \right)^2

Where:

· F_r: Minimum radial load (N)
· K_r: Minimum load coefficient
· = 100 for series 10 bearings
· = 150 for series 2, 3, and 4 bearings
· = 200 for series 22 bearings
· = 250 for series 23 bearings
· n: Rotational speed (r/min)
· n_r: Limiting speed for oil lubrication (r/min)
· d_m: Bearing mean diameter = 0.5 \times (d + D) (mm)

· Dynamic equivalent load P = F_r (kN) for cylindrical roller bearings carrying axial loads:
· For dimension series 2 and 3:
· P = F_r + 0.3F_a when 0 \leq \frac{F_a}{F_r} \leq 0.12
· P = 0.94F_r + 0.8F_a when 0.12 < \frac{F_a}{F_r} \leq 0.3
· For dimension series 22 and 23:
· P = F_r + 0.2F_a when 0 \leq \frac{F_a}{F_r} \leq 0.18
· P = 0.94F_r + 0.53F_a when 0.18 < \frac{F_a}{F_r} \leq 0.3
· Static equivalent load P_0 = F_r (kN)

Cylindrical roller bearings are primarily designed to carry radial loads. However, bearings with flanged rings (e.g., NJ, NF, and NUP types) can also accommodate certain axial loads. The axial load capacity is not determined by material fatigue strength but by the load-bearing capacity of the sliding surfaces at the contact area between the rollers and flanges. This depends mainly on the lubrication condition, operating temperature, and heat dissipation capabilities of the bearing.

The allowable axial load can be calculated using the following formula:

F_{ap} = K_1 \cdot C_0 \cdot \left(1 - \frac{F_r}{0.8C_0}\right) \cdot \left( \frac{d \cdot D}{1000} \right) \cdot \left( \frac{1000}{n} \right)^{0.5} \cdot K_2

Where:

· F_{ap}: Maximum allowable axial load (N)
· C_0: Basic static load rating (N)
· F_r: Actual radial load (N)
· n: Operating speed (r/min)
· d: Bearing inner diameter (mm)
· D: Bearing outer diameter (mm)
· K_1: Coefficient (0.3 for oil lubrication; 0.5 for grease lubrication)
· K_2: Coefficient (0.03 for oil lubrication; 0.05 for grease lubrication)

The above formula applies under normal operating conditions and is valid for constant axial loads. For temporarily applied axial loads, multiply the result by 2; for impact loads, multiply by 3.

The constant axial load F_a acting on the bearing must not exceed 1.2D^2 (where D is the outer diameter in mm). Occasional impact loads must not exceed 3D^2.

To ensure uniform flange loading and sufficient operational precision of the shaft, special attention must be paid to the axial runout of the relevant contact surfaces for cylindrical roller bearings subjected to high axial loads.

Other types of single-row cylindrical roller bearings, such as full-complement self-locking bearings, can also be produced upon customer request."