Heavy Duty Needle Roller Bearings

Heavy duty needle roller bearings

The heavy duty needle roller bearings consists of ground solid outer ring, needle roller, and cage. Its high-strength cage can effectively lock and guide the needle rollers. The oil groove and oil hole on the outer ring can also be selected according to the situation. These bearings can be classified to with or without inner rings depending on whether the shaft is suitable as a raceway.

Size: 5mm-335mm(Inner hole size)

Usage: Gear pump, pulley, car gearbox, motorcycle engine, etc

Characteristics: In relatively small installation spaces, a thick outer ring can provide maximum load-rating and seismic resistance.

Advantages: Optimize speed and lubrication endurance.

1. Metric series heavy duty needle roller bearings

The dimensions of metric series heavy duty needle roller bearings are measured in millimeters.

When the inner diameter (FW≥12mm), a structure with outer ring flanges is adopted. This structure provides axial protection for the needle rollers and cage.

When the inner diameter (FW≤10mm) , an Inserted end-washers structure design is adopted. This structure also needs to ensure that the needle rollers and cage are axially protected.

1)Metric series heavy duty needle roller bearings with inner rings

When the shaft cannot meet the conditions to work as a raceway in practical situations, then the inner ring must be used. Standard needle roller bearing can have an inner ring (such as NA series) to be a complete bearing. The inner ring of the bearing must meet the quality standards of ISO.

For the tolerances of the inner and outer rings, bearings with metric dimensions shall follow tolerance standards for conventional radial bearings covered by ISO 492. Bearings that require a higher precision class, such as P6 and P5, will be determined based on actual needs.

Metric series heavy duty needle roller bearings need to follow the radial clearance standard of ISO 5853. This standard also applies to cylindrical roller bearings. The clearance of bearings C2, C3, and C4 may be adjusted according to requirements. In most cases, bearings are still made based on C0 clearance.

The dimensions of the inner and outer chamfer must follow the standard of ISO 582.

2)Metric series heavy duty needle roller bearings without inner rings

When the shaft can be used as an inner raceway, heavy duty needle roller bearings without inner rings are more cost-effective, and it can better control the internal radial clearance during operation. The Inner diameter tolerance of metric needle roller bearing before installation is F6, as shown in Table 1 and Table 2.

For needle roller bearings like RNAO series without flanges and inner rings, the outer ring, needle rollers, and cage components cannot be interchanged.

Table 1 Bore tolerance standard for metric series bearings with cage and without inner ring

Table 2 Bore tolerance standard for metric series full complement heavy duty needle roller bearings without inner ring

3)49 series metric needle roller bearings with seals

49 series needle roller bearings can be equipped with one or two complete seals. One seal design adds the suffix RS, and two seals design adds 2RS. Bearings also need to follow corresponding standards when equipped with inner rings, the width of the inner ring is larger than the width of the outer ring to ensure effective sealing contact.

These seals make the operating temperature of the bearing limit at -30°C - 110°C (-25°F - 225°F). If the operating temperature exceeds this range, or the sealing ring is exposed to abnormal liquids, attention must be paid to the selection of external materials for the sealing rings, as well as other solutions. Bearings with seals are generally wrapped in lithium soap-based grease, and the temperature can reach 120°C (248°F) for short period of time.

The speed rating of sealed bearings is based on the operating conditions determined by testing. Proper bearing internal installation clearance can effectively improve the bearing performance and reduce vibrations. Care must be taken that the bearings do not overheat,so as to avoid damage on the grease,causing bearing failure.

4)Installation of metric heavy duty needle roller bearings

When the load is stationary relative to the mounting housing, clearance fit is suggested, When the load rotates relative to the mounting housing, use tight transition fit is suggested

Table 3 shows the recommended housing and shaft dimensions of heavy duty needle roller bearings without inner ring.

Table 4 shows the recommended housing and shaft dimensions of needle roller bearings with inner ring .

Other installation dimensions may define according to the specific situation.

For example:

① Extremely high radial load

② Impact load

③ Temperature gradient across bearings

④ Housing material with heat expansion coefficient different than that of the bearing

⑤ Applications with vibration motion applications

Table 3 Recommended housing and shaft dimensions of needle roller

bearings without inner ring .

Table 4 Recommended housing and shaft dimensions of heavy duty needle roller

bearings with inner ring

When the outer ring of the bearing is installed into the housing, it must be axially positioned, which can be located by the housing shoulder or other positive means. The outer ring of the bearing should fit tightly with the shaft and housing, and should not contact the fillet radius.The maximum fillet ra max of the shaft and housing cannot be greater than the chamfer rs min of the bearing. As shown in Table 5 below.

graphic

In order to allow the shaft to be installed or removed, the maximum diameter D1 cannot exceed Fw, as shown in Table 6

Table 6 Shoulder height D1 max dimension of metric heavy duty needle roller bearing shaft

Heavy duty needle roller bearings without flanges such as RNAO and NAO series must be positioned by the mounting housing or the rib on the shaft.(Table 7 and Table 8). Or other suitable methods, such as spring steel spacers. These positioning components must be hardened and machined, or ground to minimize wear, and properly installed to match the outer and inner rings of the bearing so as to meet the final required clearance for needle rollers and cage assembly.

Table 7 Installation dimensions of metric series heavy duty needle roller bearings without ribs (without inner ring)

Table 8 Installation dimensions of metric series heavy duty needle roller bearings

without ribs (with inner ring)

5)Bearing load factor

①Dynamic load

Heavy duty needle roller bearings can only bear radial dynamic loads.

P=Fr(KN)

P=The maximum radial dynamic load that the needle roller bearing can bear based on the rated dynamic load Cr given in the bearing table. This load should be ≤Cr/3

②Static load

Heavy duty needle roller bearings can only bear radial loads.

P0=Fr(KN)

Heavy duty needle roller bearings must have needle rollers of the same group limits to ensure uniform load distribution.

2. Inch series heavy duty needle roller bearings

The structures of inch series heavy duty needle roller bearings and metric series heavy duty needle roller bearings are generally the same, but the dimensions are in inches. If the bearing needs to have high dynamic and static load capacity and even impact resistance capability in a limited installation space, heavy duty needle roller bearings are the best choices.

1) Usually the part numbers prefixed HJ, NCS, MR, BR, etc. are all with inch sizes. The part numbers prefixed IR are inch sized inner rings

2) Lubrication of inch series heavy duty needle roller bearings

The outer ring of the HJ series bearings has an oil groove,and a lubricating oil hole on this oil groove to ensure that oil can be injected from the outer ring for re-lubrication. There is also a lubricating oil hole on IR inner ring to ensure that oil can be re-lubricated from the inner ring as well.

HJ series bearings (with or without sealing rings) must be protected against rust during transportation. These protections do not refer to lubrication and are determined according to customer requirements. The grease for this type of bearing may also be customer specified.

3) Installation of inch series heavy duty needle roller bearings

Like metric series heavy duty needle roller bearings, when the load is stationary relative to the housing. It is suggested to use a clearance fit. When the load rotates relative to the housing, then tight transition fit is suggested. Because the tight-fitting installation can reduce the inner bore of the bearing, the diameter of the raceway of the shaft can also be slightly reduced.

When the bearing is installed with a clearance fit, the recommended tolerance of the mounting housing is ISO H7, and the recommended tolerance of the shaft raceway is ISO h6.

When the bearing is installed with a tight transition fit, the recommended tolerance of the housing is ISO N7, and the recommended tolerance of the shaft raceway is ISO f6.

Other installation dimensions may be determined on a practical basis.

For example:

① Extremely high radial load

② Impact load

③ The load rotates relative to both the inner and outer rings

④ Temperature gradient across bearing

⑤ The thermal expansion coefficient of the mounting housing is different from that of the bearings

4)Dimensional accuracy of inch series heavy duty needle roller bearings

The accuracy of HJ series bearings is based on Table 9 and Table 10, and the accuracy of the IR series inner ring is based on Table 11 and Table 12

Table 9 Outer diameter and height tolerances of inch series heavy duty needle roller bearings

Table 10 Bore dimensional tolerances of inch series heavy duty needle roller bearings

Table 11 Bore and height tolerances of IR inch series inner rings

Table 12 Outer diameter tolerance of IR inch series inner ring