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TYPES AND FEATURES OF ROLLING BEARINGS
Single-Row Single-row deep groove ball bearings are the most common type of rolling bearings. Their use
Deep Groove is very widespread. The raceway grooves on both the inner and outer rings have circular arcs of
Ball Bearings slightly larger radius than that of the balls. In addition to radial loads, axial loads can be imposed
in either direction. Because of their low torque, they are highly suitable for applications where high
speeds and low power loss are required.
In addition to open type bearings, these bearings often have steel shields or rubber seals installed
on one or both sides and are prelubricated with grease. Also, snap rings are sometimes used on
the periphery. As to cages, pressed steel ones are the most common.
Magneto The inner groove of magneto bearings is a little shallower than that of deep groove bearings.
Bearings Since the outer ring has a shoulder on only one side, the outer ring may be removed. This is often
advantageous for mounting. In general, two such bearings are used in duplex pairs. Magneto
bearings are small bearings with a bore diameter of 4 to 20 mm and are mainly used for small
magnetos, gyroscopes, instruments, etc. Pressed brass cages are generally used.
Single-Row Individual bearings of this type are capable of taking radial loads and also axial loads in one
Angular Contact direction. Four contact angles of 15°, 25°, 30°, and 40° are available. The larger the contact angle,
Ball Bearings the higher the axial load capacity. For high speed operation, however, the smaller contact angles
are preferred. Usually, two bearings are used in duplex pairs, and the clearance between them
must be adjusted properly.
Pressed-steel cages are commonly used, however, for high precision bearings with a contact angle
less than 30°, polyamide resin cages are often used.
Duplex Bearings A combination of two radial bearings is called a duplex pair. Usually, they are formed using angular
contact ball bearings or tapered roller bearings. Possible combinations include face-to-face, which
have the outer ring faces together (type DF), back-to-back (type DB), or both front faces in the
same direction (type DT). DF and DB duplex bearings are capable of taking radial loads and axial
loads in either direction. Type DT is used when there is a strong axial load in one direction and it is
necessary to impose the load equally on each bearing.
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Double-Row Double-row angular contact ball bearings are basically two single-row angular contact ball bearings
Angular Contact mounted back-to-back except that they have only one inner ring and one outer ring, each having
Ball Bearings raceways. They can take axial loads in either direction.
Four-Point The inner and outer rings of four-point contact ball bearings are separable because the inner ring
Contact is split in a radial plane. They can take axial loads from either direction. The balls have a contact
Ball Bearings angle of 35° with each ring. Just one bearing of this type can replace a combination of face-to-face
or back-to-back angular contact bearings.
Machined brass cages are generally used.
Self-Aligning The inner ring of this type of bearing has two raceways and the outer ring has a single spherical
Ball Bearings raceway with its center of curvature coincident with the bearing axis. Therefore, the axis of the
inner ring, balls, and cage can deflect to some extent around the bearing center. Consequently,
minor angular misalignment of the shaft and housing caused by machining or mounting error is
automatically corrected.
This type of bearing often has a tapered bore for mounting using an adapter sleeve.
Cylindrical In bearings of this type, the cylindrical rollers are in linear contact with the raceways. They have a
Roller Bearings high radial load capacity and are suitable for high speeds.
There are different types designated NU, NJ, NUP, N, NF for single-row bearings, and NNU, NN for
double-row bearings depending on the design or absence of side ribs.
The outer and inner rings of all types are separable.
Some cylindrical roller bearings have no ribs on either the inner or outer ring, so the rings can
move axially relative to each other. These can be used as free-end bearings. Cylindrical roller
bearings, in which either the inner or outer rings has two ribs and the other ring has one, are
capable of taking some axial load in one direction. Double-row cylindrical roller bearings have high
radial rigidity and are used primarily for precision machine tools.
Pressed steel or machined brass cages are generally used, but sometimes molded polyamide
cages are also used.
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