Tapered roller thrust bearings of this type must be able to accommodate extremely heavy axial loads and also permit angular movement of the screw spindle with respect to the support. The bearings are therefore generally of the full complement type and have extremely long rollers of large diameter. To be able to accommodate the alignment movements of the chock without detrimental effect on bearing performance, the bearings have one sphered washer. This may be either the shaft washer  or the housing washer .

The necessary alignment movements take place in bearings having a sphered shaft washer above the roller complement between the sphered shaft washer and a correspondingly concave sphered screw spindle or pressure plate . The pressure plate can also be supplied by SKF.

Where the housing washer is sphered, the alignment movements are accommodated below the roller complement between the housing washer and the pressure plate. The pressure plate for these bearings is always supplied with the bearing.

SKF produces many designs of screw-down bearing; they are tailored to meet the particular requirements of the specific application.

Cylindrical roller thrust bearings are suitable for arrangements that have to support heavy axial loads. Furthermore, they are relatively insensitive to shock loads, are very stiff and require little axial space. As standard they are available as single direction bearings and can only accommodate axial loads acting in one direction.

Cylindrical roller thrust bearings are simple in form and design and are produced in single row and double row designs. The bearings in the 811 and 812 series are mainly used where thrust ball bearings have insufficient load carrying capacity.

The cylindrical surface of the rollers is slightly relieved towards the ends. The resulting contact profile virtually eliminates damaging edge stresses. The bearings are of separable design; the individual components can be mounted separately.

Single direction thrust ball bearings
SKF single direction thrust ball bearings consist of a shaft washer, a housing washer and a ball and cage thrust assembly. The bearings are separable so that mounting is simple as the washers and the ball and cage assembly can be mounted separately.

Smaller sizes are available with either a flat seat surface on the housing washer  or a sphered seat surface . Bearings with a sphered housing washer can be used together with a sphered seat washer  to compensate for misalignment between the support surface in the housing and the shaft. Sphered seat washers are available from SKF but must be ordered separately.

Single direction thrust ball bearings, as their name suggests, can accommodate axial loads in one direction and thus locate a shaft axially in one direction. They must not be subjected to any radial load.

In addition SKF also offers polymer thrust ball bearings, shown in the section “Engineering products – Polymer ball bearings”.

Double direction thrust ball bearings
SKF double direction thrust ball bearings consist of one shaft washer, two housing washers and two ball and cage thrust assemblies. The bearings are separable so that mounting is simple. The various parts can be mounted separately. The housing washers and ball and cage thrust assemblies are identical to those of the single direction bearings.

Smaller bearings are available with either a flat seat surface on the housing washers  or with a sphered seat surface . Bearings with sphered housing washers can be used together with sphered seat washers  to compensate for misalignment between the housing and shaft. The sphered seat washers are available from SKF, but must be ordered separately.

Double direction thrust ball bearings can accommodate axial loads acting in both directions and can thus serve to axially locate a shaft in both directions. They must not be subjected to radial load.

Spherical roller bearings have two rows of rollers with a common sphered raceway in the outer ring and two inner ring raceways inclined at an angle to the bearing axis . This gives them an attractive combination of design features making them irreplaceable in many demanding applications. They are self-aligning and consequently insensitive to misalignment of the shaft relative to the housing and to shaft deflection or bending.

SKF spherical roller bearings are leading in design and can, in addition to high radial loads, accommodate high axial loads acting in both directions.

The standard range of SKF spherical roller bearings comprises

–  open bearings
–  sealed bearings
–  bearings for vibratory applications.

In addition to the standard range, SKF offers a wide range of special spherical roller bearings adapted for specific applications.

Drawn cup needle roller bearings, as the name suggests, are needle roller bearings with a deep drawn, thin-walled outer ring with either open ends or a closed end. They are characterized by a very low sectional height and high load carrying capacity. Drawn cup needle roller bearings are typically used in applications where the housing bore cannot be used as a raceway for a needle roller and cage assembly, but where a very compact and economical bearing arrangement is required.

Generally, drawn cup needle roller bearings have a recommended maximum operating temperature of 140 °C, unless otherwise stated in the relevant sections in this chapter. The maximum operating temperature is limited by the seal and cage materials and the applied grease.

SKF supplies a wide assortment of drawn cup needle roller bearings. This includes:

– drawn cup needle roller bearings with open ends
– drawn cup needle roller bearings with a closed end
– full complement drawn cup needle roller bearings with open ends

Drawn cup needle roller bearings with a closed end are suitable for bearing arrangements at the ends of shafts. The profiled design of the closed end accommodates small axial guidance forces. Drawn cup needle roller bearings generally run directly on the shaft. However, in cases where the shaft cannot be hardened and ground, they can be combined with an inner ring .

The self-aligning ball bearing was invented by SKF. It has two rows of balls and a common concave sphered raceway in the outer ring. The bearing is consequently self-aligning and insensitive to angular misalignments of the shaft relative to the housing. It is particularly suitable for applications where considerable shaft deflections or misalignment are to be expected. Additionally, the self-aligning ball bearing has the lowest friction of all rolling bearings, which enables it to run cooler even at high speeds.

SKF produces self-aligning ball bearings to several designs. These are

– open bearings of the basic design
– sealed bearings
– open bearings with an extended inner ring .

To better understand frequently used bearing specific terms for

– Y-bearings
– Y-bearing plummer block units
– Y-bearing flanged units
– Y-bearing take-up units

the terms and their definitions are provided below. Essentially these terms con-form to those found in the following ISO standards:

– ISO 3228:1993 “Rolling bearings – Cast and pressed housings for insert bearings”.
– ISO 9628:1992 “Rolling bearings – Insert bearings and eccentric locking collars”.

A detailed collection of bearing specific terms and definitions can be found in ISO 5593:1997 “Rolling bearings – Vocabulary”.

Y-bearing

1 Outer ring
2 Sphered outer surface
3 Lubrication hole
4 Inner ring
5 Bore
6 Cage
7 Ball
8 Superagriseal
9 Flinger
10 Eccenteric locking collar
11 Grub screw

In spherical roller thrust bearings the load is transmitted from one raceway to the other at an angle to the bearing axis . The bearings are therefore suitable to accommodate radial loads in addition to simultaneously acting axial loads. Another important characteristic of spherical roller thrust bearings is their self-aligning capability. This makes the bearings insensitive to shaft deflection and misalignment of the shaft relative to the housing.

SKF spherical roller thrust bearings incorporate a large number of asymmetrical rollers and have specially designed raceways with an optimum conformity. They can therefore support very heavy axial loads and permit relatively high speed operation.

SKF spherical roller thrust bearings are produced in two designs depending on the size and series. Bearings up to and including size 68 identified by the designation suffix E have a pressed steel window-type cage which, with the rollers, forms a non-separable assembly with the shaft washer . All other bearings have a machined brass or steel cage which is guided by a sleeve held in the shaft washer bore . The shaft washer and cage with rollers form a non-separable unit.

SKF needle roller thrust bearings in the AXW series  consist of a needle roller and cage thrust assembly and a thrust washer with a centring spigot. The spigot facilitates the mounting process of the thrust bearing and provides an accurate radial centring of the housing washer. Available bore sizes for the thrust assembly range from 10 to 50 mm.

Combination with radial needle roller bearings
To accommodate combined radial and axial loads, AXW series needle roller thrust bearings can be combined with the following radial needle roller bearings:

– drawn cup needle roller bearings with a closed end or with open ends
– needle roller bearings with machined rings

These arrangements provide an economical and compact solution for combined loads.