Did You Know? Giant Roller
Bearings
Probably the first use of a bearing was back when the Egyptians
were building the pyramids. They put round logs under the heavy
stones so that they could roll them to the building site.
This method is still used today when large, very heavy objects like
the Cape Hatteras lighthouse need to be moved. |
Self aligning ball bearings are suitable for
applications where misalignment can arise from errors in mounting or
shaft deflection. The steel balls, cage, and inner ring can rotate
freely at a certain angle, as it is stated that the bearings have
self-aligning features. Accordingly, misalignment of the bearing shaft
due to the machining and installation of the shaft and housing will be
automatically adjusted.
Physical Characteristics 
- The self-aligning ball bearing has two rows of balls.
- A common concave sphered raceway in the outer ring.
- The center of whose curvature meets that of the bearing itself,
so that the inner ring, balls and cage continue to rotate.
- The self-aligning ball bearing with a tapered bore can easily be
fit to the shaft with an adapter assembly.
Advantages Of Deep Groove Ball Bearings
- Have the lowest friction of all rolling bearings.
- Run cooler even at high speeds.
- Easy mounting and dismounting.
- The permissible operating speed is not dependent on the common
criteria like heat generation or cage stability and strength.
Application Of Deep Groove Ball Bearings
- Self-aligning ball bearings are used for commercial ground
shafting applications.
- Since axial load capacity is limited, self-aligning ball bearings
are not suitable for applications with heavy axial loads.
- Furthermore, if an adapter is used on the tapered bore of the
inner diameter, installation and disassembly are much simpler and
for this reason adapters are often used on equipment with drive
shafts.
Buying Tips
Consider the followings before you go and shop for self aligning
bearings:
- Allowable misalignment angle
- Operational costs
- Hardness at operating temperature
- Temperature at high speed
- Cage materials
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Types Of Self Aligning Ball Bearings
The two basic designs of double row self-aligning ball bearings are
standard and "E" shaped. The "E" shaped have a
larger load carrying capacity and can be used in a wider range of
applications.
They are available in three designs:
- Basic open design - These self aligning
bearings may have a cylindrical or a taper bore. The one with a
taper bore requires adapter sleeves with locking washers with which
the bearings can be secured on to the shafts.
- Sealed Bearings - The sealed bearings have
seals on both sides. They are made of oil and synthetic rubber with
a sheet steel reinforcement. Operating temperature is -40° C to
120° C. The outside diameter of the seal is retained in a
recess in the outer diameter forming a tight seal are filled with a
lithium based grease that inhibits rust and can operate on
temperature ranging from -30°C to 110°C. These self
aligning bearings may have a cylindrical or a taper bore. The one
with a taper bore requires adapter sleeves with locking washers with
which the bearings can be secured on to the shafts.
- Bearings with Extended Inner Ring - This type
of self-aligning ball bearings are used for commercial ground
shafting applications. The bore tolerance allows easy mounting and
dismounting. They are located axially by pins or screws that fix in
a slot on one side of the inner ring. This also prevents the inner
ring from turning on the shaft. When used in pairs the slots should
either be adjacent or at the outboard position.
Self Aligning Ball Bearings Specifications & Standards
- Standard cage types - All bearing series are
equipped with a pressed cage, except 2322S, which is equipped with a
machined cage.
- Dimensions -The dimensions are as per the ISO
recommendations.
- Misalignment - They are designed to adjust to
the angular misalignment from one bearing to the other within the
permissible limits.
- Tolerance - They are usually meant for normal
tolerance but can be enhanced.
- Ball protrusion - Bearings with part numbers
listed in the diagram below have balls which protrude slightly from
the bearing face. Their degree of protrusion is listed below:
 
- Allowable misalignment angle - Allowable
misalignment under normal loads (loads equivalent to 0.09 Cr): 0.07
rad (4°).This degree of allowable misalignment may be limited
by the design of structures around the bearing.
- Internal Clearance -The normal radial internal
clearance is taken as standard in cylindrical as well as tapered
bore but there may be certain variations. The extended inner ring
radial internal clearance is C3 + Normal.
Click
Here to view Radial internal clearance of self-aligning ball
bearings
- Cages - There are standard cages but some may
have pressed steel cage, glass fiber reinforced, or machined brass
cages.
- Minimum Load - For satisfactory operation, the
bearings must be subjected to the minimum load that is calculated
by:
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