Thursday, December 8, 2022

How does the bearing extractor work?

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The removal or disassembly of bearings (bearings or bearings) is a complicated task that must be carried out with great care in order to avoid damage to the bearing, to the other components of the machine or the motor, such as the shaft, the support, etc., and even for safety of the operator himself.

Many do the removal of bearings striking these with a hammer or chisel, a method that should be avoided as much as possible due to the potential risk of damage, not only to the bearing (unless it is already unusable) but also to the casing that contains it, the shaft, housings, etc.

For the correct disassembly of bearings, tools called bearing extractors, which perform the operation in a simple and efficient way. Depending on their design, pullers can be used to either mount or dismount bearings from a motor housing or machine cavity. The operation is simple: a part of the extractor must press against the housing, while another internal part pushes the bearing in or out of its compartment. By applying pressure evenly, without impact, the extractor acts on the bearing without any damage to the housing that contains it.

Since there are various types and sizes of extractors that correspond to the different arrangement of bearings, with applications ranging from a pair of skates to bicycles, household tools, motors and complex industrial machinery, the selection of the extractor must be done carefully, so choose the right tool for the particular bearing you want to remove.

Steps to choose the right extractor

1) Identify the type of mounting or arrangement of the bearing, that is: if it has a cylindrical seat, conical seat, adapter sleeve or withdrawal sleeve.

2) Select the extraction method to use, that is: mechanical, hydraulic, by oil injection or by heating.

The method is selected according to the size of the bearing, measured by the diameter of the hole, that is: small bearings (hole diameter less than 80 mm), medium bearings (hole diameter between 80 and 200 mm), and large bearings. (hole more than 200 mm in diameter).

The following table shows the recommended removal method based on bearing size/type and arrangement.

Bearing extractor selection

3) Select the correct type of extractor: dDepending on the bearing to be removed, there are a wide variety of tools available. Some are mentioned below, depending on the bearing to be extracted.

a) Removal of sprockets, rollers and ball bearings, belt pulleys and similar parts from a shaft or axle

  • Two or three arm pullers with extraction claws.
bearing extractor

bearing extractor

Whenever possible, the three arm puller It is the most recommended due to the best load distribution. Both in two-arm and three-arm models, a wide variety of shapes and sizes are available, the latter generally cataloged by the parameters shown in the following image and which are adapted to each Bearing in particular.

Bearing puller selection parameters

Bearing puller selection parameters

to all these extractors you can attach a hydraulic device, in order to allow the extraction of larger and/or tightly fitted components, without using the physical force of the operator. The following figure shows an example of three-arm hydraulic puller.

hydraulic puller

hydraulic puller

b) Extraction of ball bearings, roller bearings, bushings and other sealed seat parts

  • Separating devices and separating-extractors.
Extractor-separator

Extractor-separator

These tools are very useful in cases where conventional extractors cannot be used due to extremely narrow spaces. It consists of two independent pieces: a separator and the extractor itself, selected for the particular case based on the parameters shown in the following image.

Separator and extractor selection parameters

Separator and extractor selection parameters

This compound tool is indicated in cases where the inner ring is tight against the shaft shoulder and there are no extraction grooves. To do this, both halves of the spacer are inserted between the shaft shoulder and the inner ring by alternately tightening the nuts. The spreader device is screwed with two rods that are attached to the cross arm of the extractor. The bearing or inner ring is extracted by screwing the spindle.

c) Extraction of ball bearings

In the case of ball bearings that do not have radial access and with a tight outer ring, are used extractors where the claws grip the edge of the outer ring raceway between the balls and bear against the inner ring. The bearing is extracted by means of a threaded spindle.

Ball bearing extractor

Ball bearing extractor

other model of ball bearing extractor is he internal extractor, suitable for deep groove ball bearings, angular contact ball bearings and bearings with a tightly fitted outer ring. The parameters that catalog the various internal extractors are those shown in the following image, so it can be seen that these extractors are only used with small diameters.

Internal extractor parameters

Internal extractor parameters

It is important to note that there are many other variants of bearing extractors (only the most used have been indicated) and their cost depends on the demand for the tool. Some pullers are common and can be found for a reasonable price at an auto parts dealer. Others are highly specialized and can be extremely expensive, but the important thing is that there is practically a bearing extractor for each and every one of the needs, both for general and domestic use, as well as for the automotive and heavy machinery industry.

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