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产品描述

NEEDLE BEARINGS

PRODUCT OVERVIEW

LIST OF CONTENTS

Radial needle roller and cage assemblies

Needle bushes

Bearings with cageGuided needles

Full complement needle bearings

Cam followers

Needle thrust bearingsRoller thrust bearings

Combined bearings

Sealing rings

Needle rollers

Summary tableInner rings

Tolerances tables

Code symbols

PRODUCT OVERVIEW

TECHNICAL FEATURES

1. GENERAL

The choice of a bearing depends on many factors that need to be examined in order to obtain the most successful results at the lowest cost.

In most cases the selection should be made when the overall design of the machine has been decided.

Dimensional limits are then known, also the speeds and loads. At this stage the choice can be made from the many types of bearings offered from the standard ranges. The notes given in this section will generally permit one to select the most suitable bearing for each application.

As for all other types of bearing, the results obtained with needle bearing products depend to a large extent on the design and method of assembly, loading, and alignment between inner and outer rings.

Bearing alignment depends first of all on the geometry of the parts involved and secondly on the deflection of the shaft under load. The shaft diameter should therefore be sufficient to prevent large deflections. This is easier to achieve using needle bearings because they occupy a small radial area.

2. BEARING TYPE SELECTION

Bearing type selection is made after the general design concept of the mechanism has been established and the application requirements carefully evaluated.

The ability of a bearing to support radial or axial loads, tolerate misalignments, be suitable for high speeds or loads are the main criteria for guiding the selection in the correct way. To navigate the families of bearings in this catalogue an initial assessment can be made on the basis of the table below. Further details are specified in the relevant chapters.

3. CALCULATIONS FOR RADIAL AND THRUST BEARINGS

The details following enable one to evaluate lifetime of radial bearings and thrust bearings and also combined bearings which comprise a radial and a thrust component. These are calculated separately without transforming the axial load into an equivalent radial load. 

The calculation for a radial or thrust bearing must take account of the following principal factors: 

• Actual supported loads and possible shock loads

• Rotation speed

• Operating temperature

• Hardness of the bearing raceways

Other features such as lubrication, sealing and alignment must be considered in order to avoid introducing unfavourable factors.

The formulas for lifetime calculations here reported are considered valid under standard conditions, generally useful for first-sizing or product comparison.For further details on correction factors for bearing lifetime in applications, please refer to ISO281 standards and to Nadella Technical 

Service.

The life calculation of a radial bearing or a thrust bearing under rotation is established from the dynamic capacity C indicated in the tables of dimensions. The static capacity Co enables one to determine the maximum load under certain operating conditions (see table above).

PRODUCT OVERVIEW

APPLICATIONS

OFFSET PRESS- PAPER FEEDING MECHANISM

The pinion shaft is supported at one end, by two RAX 730 thin wall combined bearings, which ensure lateral location in both directions. The other end of the shaft runs in a HK 30 20 caged needle bushes.

The use of inner race avoids the necessity for hardening the shaft journals. The use of inner race avoids the necessity for hardening the shaft journals.

FOLLOWERS FOR OVERHEAD CONVEYOR

The common spindle carrying the two rollers turns between two RAX 718 combined bearings (with thrust plates) which ensures lateral location in both directions. The bearing surfaces of the shaft are hardened to 58 HRC.

Lubrication is by grease introduced via a nipple on the end of the shaft. Sealing is effected by sealing rings type DH28x35x4.

MILLER/BORER - GEAR BOX

This assembly is particularly interesting in the method of radial and axial location of gears and spindles, by means of two RAX 400 combined bearings mounted in opposition which, even though located in close proximity, ensure adequate support. Of equal interest is the RAX 700 thin wall combined bearing whose closed end ensures perfect shaft sealing.

BORER SPINDLE

Case hardening the ends of the shaft to 60 HRC allows the use of bearings without inner rings. The front journal is a combined bearing with roller thrust and integral thrust washer. The inside diameter of the radial part of the bearing is held to tolerance F6, and the shaft to k5, giving the necessary low play for this precision application.

The thrust rollers of the combined bearing withstand the main axial loading. lt is shielded from ingress of foreign bodies by the cover which retains the thrust washer and by a sleeve over the assembly. The rear housing incorporates an RAX 417 combined bearing (with thrust washer CP 2 17 30) on a k5 shaft. the needle thrust taking the axial loadings in the opposite direction to the main working load. A speed of 1 500 r.p.m. allows the use of grease for lubrication.

HAND DRILL

This example shows the use, on a hardened shaft, of type HK caged needle bushes, whose small radial thickness is particularly suitable for this type of application. The outer bearing of the output shaft is supported by a HK sealed, caged needle bush. Axial drilling loads are carried by a needle thrust bearing type AX.

ROLLING MILL FOLLOWER

This roller guides hot rolled steel products whose temperature is around 100°C. A cooling spray limits the temperature of the roller to 50°C. Two NA 3 080 full complement bearing support the radial load which may be as high as 28 000 daN at a speed of 100 r.p.m.

Axial location of the rollers is by two AX needle thrust bearings of 90 mm bore, mounted either side of a CPR intermediate plate. Lip seals an d grease filledlabyrinths effectively prevent the ingress of coolant into the bearing

GEAR PUMP

The operating conditions of this gear pump allow the use of DL and DLF full complement needle bushes bearings on the pinion journals. The DLF closed end needle bushes ensure the sealing of the bores in the bottom plate. The trunnions, acting as raceways under the needles, are hardened to 58 HRC.

RIGHT-ANGLE GEAR BOX

The driving shaft runs in two combined bearings types RAX 718 and RAX 720 with separate thrust plates. The driven shaft is mounted on two RAX 720 combined bearings of which one only has a separate thrust plate. The shaft journals and gear faces serving as bearing raceways are hardened to 58 HRC. The sealing of all shafts is ensured by type DH 20 26 sealing rings.

DRUM SUPPORT ROLLERS

These rollers are each fitted with two NK 42/20 caged needle bearings with inner rings. A SW sealed cam follower with stud mounted vertically between the flanges of the sleeve, ensures lateral location of the cylinder in both directions.

This arrangement offers the following advantages:

- The bearings are determined by the load to be carried rather than by the diameter of the trunnion. It is clearly preferable to sue four small bearings, rather than one of unnecessarily large diameter.

- When the drum is heated internally, only a small amount of heat is transferred to the bearings via the outside diameter and the bearings do not have to have specially increased play to allow for expansion of the inner rings, as would be the case with a large bearing mounted on the trunnion.

- Finally the coefficient of friction is much reduced and less power is required to turn the cylinder.

HAND OPERATED VALVE

Threaded spindle support mounted between two needle thrust bearings, i.e. AX 45 65 (with matching thrust races) ensures .low frictional characteristics and easy manual operation.

"RAPIER" WEAVING MACHINE

On this type of weaving machine, the shuttles are replaced by "spears" or "rapiers" whose function is to project the weft thread through the warp threads to produce larger widths of cloth. The fore and aft operation of these "rapiers" is by means of a system of connecting rods whose arms are fitted with NA 22 030 full complement needle bearings (with inner races) which fully cater for the shock loadings occasioned by reversals of directions. either rotationally or under oscillating movement.