MRO Magazine

Top tools for working with bearings

Bearings are made to exacting tolerances and have very fine surface finishes. In order to maintain the geometrical precision and the surface integrity of ball and roller bearing raceways and rolling elements, it is mandatory that care in...


Machinery and Equipment Maintenance

April 1, 2012
By Bearing Specialists Association

Bearings are made to exacting tolerances and have very fine surface finishes. In order to maintain the geometrical precision and the surface integrity of ball and roller bearing raceways and rolling elements, it is mandatory that care in storage, handling and installation be observed.

Although the hardened bearing steel used to manufacture bearing components can withstand heavy pressures during operation, bearings are vulnerable to the stresses of metal-to-metal contact that occur when they are mishandled. When a bearing is bumped or dropped, rolling contact damage usually results. Either the raceways are dented (brinelled) or scuffed. Damaged areas become the focal points for premature failure.

The best way to ensure the maximum performance and anticipated life from rolling bearings is taking extreme care during the installation process. Using the proper installation tools is the first step in assuring a successful result.

Preparation is the key to any successful bearing installation. Before a bearing is drawn from its place of storage, an organized work area must be created that ensures cleanliness, safety and easy access to all of the required tools.

The bearing installation tools discussed here are applicable to a variety of sizes and styles of bearing. However, they may not work in all situations, so care must be taken when you make your selection. It’s important to use proper bearing installation tools in order to avoid the misuse of hammers, chisels, screwdrivers, torches and other general tools that could contribute to permanent bearing damage.

Small- and medium-size bearings with interference-fit inner rings are commonly mounted with the aid of a bearing heater. The purpose of the bearing heater is to expand the inner ring enough so that the bearing can be slipped on to the shaft, up to the shoulder, without the use of force.

Bearing heaters have many advantages, but they also can destroy a bearing very quickly. Bearings heaters should be equipped with certain safeguards to prevent permanent bearing damage.

For example, a bearing heater should have a timing cycle. This timer turns the heater on and off every few seconds until the bearing reaches its selected temperature. This will prevent brinelling from rapid heating.

In order to prevent overheating, a bearing heater should be equipped with a temperature probe. If this is not the case, other monitoring procedures must be employed.

Since the bearing becomes magnetized during heating, some heaters feature a demagnetizing cycle. It is strongly recommended that you use a heater with this feature.

When installing tapered bore bearings that utilize an adapter sleeve and locknut, a hook spanner wrench is needed to complete the assembly and set the clearance. The spanner is a specialized wrench with pins or tabs around the circumference. These pins or tabs fit into the notches of a locknut. The 90° spanner is the most common; however the 180° spanner requires less effort, since more of the force applied at the handle is translated to torque on the nut.

When it becomes necessary to remove a bearing from an assembly, care must be taken to avoid damage to raceways and rolling elements. In these instances, use a bearing puller. There are wide variety of sizes, capacities and styles from which to choose.

Occasionally, it becomes necessary to lightly strike a bearing in order to accomplish installation or removal. In this instance, a dead-blow hammer is recommended. This type of hammer is manufactured of a hard plastic with the head filled with a shot material to deaden the blow and prevent bounce-back of the head.

The installation of large-diameter bearings often requires the use of hydraulic equipment for mounting and removal. This makes the job easy and fast and eliminates the huge physical effort needed to do the job. Hydraulics are commonly used for tapered bore bearings and occasionally for cylindrical bore bearings.

Hydraulic fluid is pumped through the shaft to a groove under the bearing, where the hydraulic pressure expands the inner ring. This eliminates the force required to stretch the inner ring as it is being driven up the taper. The inner ring can be mounted using a standard nut or a hydraulic nut.

Hydraulic nuts are made by a number of manufacturers but all employ the same principle: A nut of standard thread is modified so that there is a hydraulic ram sealed in the inboard face. The ram is actuated by hydraulic fluid introduced through the O.D. of the nut. Pressure against the outboard face of the inner ring drives the bearing up the tapered journal.

MRO

 This is an edited version of the Bearing Mounting Tools Bearing Brief prepared by The Bearing Specialists Association (BSA) for distributors, manufacturers and end-users. Over the past several years, the association’s Educational Services Committee has published 25 Bearing Briefs.

 

To view the full layout of this article with images, as it originally appeared, see page 16 of the April 2012 issue. The digital edition of this issue can be found here:

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