Super-precision angular contact ball bearings

48 Pages·2012·1.86 MB·English

Super-precision angular
contact ball bearings:
High-speed, B design,
sealed as standard
S719 .. B (HB .. /S) and S70 .. B (HX .. /S) series
Contents
The SKF brand now stands for more A Product information C Product data
than ever before, and means more
to you as a valued customer. SKF sealed super-precision Bearing data – general ............ 20
angular contact ball bearings in the Boundary dimensions ............. 20
While SKF maintains its leadership as a S719 .. B (HB .. /S) and S70 .. B Chamfer dimensions .............. 20
high-quality bearing manufacturer (HX .. /S) series .................. 3 Tolerances ...................... 20
throughout the world, new dimensions Bearing preload .................. 21
in technical advances, product support The assortment ................. 4 Bearing axial stiffness ............. 25
and services have evol ved SKF into a High-speed, B design bearings ....... 5 Fitting and clamping of bearing rings .. 26
truly solutions-oriented supplier, Bearing series ................... 5 Load carrying capacity of bearing sets . 27
creating greater value for customers. Bearing variants .................. 6 Equivalent bearing loads ........... 27
Single bearings and matched Attainable speeds ................. 28
These solutions enable customers to bearing sets ..................... 7 Cages .......................... 29
improve productivity, not only with Seals .......................... 29
breakthrough application-specific prod- Applications .................... 8 Materials ....................... 29
ucts, but also through leading-edge Heat treatment .................. 29
design simulation tools and consultancy Marking of bearings and bearing sets .. 30
services, plant asset efficiency mainte- B Recommendations Packaging ...................... 31
nance program mes, and the industry’s Designation system ............... 31
most advanced supply management Bearing selection ................ 10
techniques. Product tables ................... 34
Bearing arrangement design ....... 11
The SKF brand still stands for the very Single bearings. . . . . . . . . . . . . . . . . . . 11
best in rolling bearings, but it now Bearing sets ..................... 11 D Additional information
stands for much more. Type of arrangement .............. 12
Application examples .............. 14 Setting the highest standard for
SKF – the knowledge engineering precision bearings ............... 42
company Lubrication and maintenance ...... 16 Super-precision angular contact ball
Sealed bearings .................. 16 bearings ........................ 42
Grease lubrication for Super-precision cylindrical roller
open bearings ................... 16 bearings ........................ 43
Running-in of sealed and open, Super-precision double direction angular
grease lubricated bearings .......... 17 contact thrust ball bearings ......... 43
Oil lubrication for open bearings ...... 18 Super-precision angular contact thrust
ball bearings for screw drives ........ 43
Super-precision axial-radial cylindrical
roller bearings ................... 43
SKF – the knowledge engineering
company ....................... 46
2
SKF sealed super-precision
A
angular contact ball bearings in
the S719 .. B (HB .. /S) and
S70 .. B (HX .. /S) series
When contaminants, such as wood dust or Ready-to-mount sealed super-precision Machine tool design is becoming increas-
swarf, get between the balls and raceways angular contact ball bearings in the ingly complex, particularly for multiple axis
of a precision bearing, damage in the con- S719 .. B (HB .. /S)1) and S70 .. B (HX .. /S) machining centres. Exceptional demands
tact areas is almost inevitable. When cutting series are characterized by: are placed on the main sub-assemblies such
fluid enters the bearing, it reduces the as the drives. SKF sealed super-precision
effectiveness of the lubricant, making the • high-speed capability angular contact ball bearings provide opti-
bearing susceptible to corrosion, higher op- • high stiffness mum performance in applications where
erating temperatures and accelerated wear. • extended bearing service life there is a need for high reliability and super-
The end result of both of these scenarios • low heat generation ior accuracy. The bearings are filled with
is high maintenance costs combined with • compact cross section high-speed grease. Non-contact seals keep
lost revenues from unplanned downtime the grease in and contaminants out of the
and lost production. bearings, with the lowest possible tempera-
SKF sealed super-precision bearings can ture rise and without compromising speed
virtually eliminate the problem of premature capability.
bearing failures resulting from contamina- These relubrication-free bearings are
tion. Where open bearings with external particularly suitable for metal cutting and
seals have been previously used, sealed woodworking machines.
super-precision bearings provide superior
performance.
1) Where applicable, designations in parentheses and italics refer to the corresponding SNFA equivalent.
3
The assortment
Sealed angular contact ball bearings in the The bearings are manufactured to two Bearings in the S719 .. B (HB .. /S) and
S719 .. B (HB .. /S) and S70 .. B (HX .. /S) tolerance classes and accommodate shaft S70 .. B (HX .. /S) series, like all angular con-
series have now been added to the SKF diameters ranging from 30 to 120 mm. tact ball bearings, are nearly always adjust-
assortment of super-precision bearings. Those suitable for universal matching or ed against a second bearing to balance the
To accommodate the diverse operating mounting in sets are produced to three counterforces. To accommodate increased
requirements of precision applications, preload classes. The bearings are fitted, loads and axial loads in both directions, the
bearings in these series are available with standard, with a seal on both sides. Bear- bearings are used in sets consisting, typic-
three contact angles and two ball materials. ings without seals are also available. ally, of up to four bearings. Matched bearing
sets with a special preload can be supplied
on request.
SKF sealed super-precision angular contact ball bearings: High-speed, B design
Features Benefits
• Ready-to-mount • Shorter mounting time
• Non-contact seals • Prevent entry of contaminants, relubrication-free, extended bearing service life
• High-speed grease • High-speed capability, good thermal stability
• Maximum number of very small balls • Provide a high degree of rigidity
• P4A or PA9A tolerance classes • Superior running accuracy, short running-in time
• Optimized chamfer design • Facilitated mounting
• ISO 19 and 10 dimensions series • Compact cross sections
• Asymmetrical inner and outer rings • Accommodate radial loads, and axial loads in one direction
• Lightweight phenolic resin cage • Low friction, high-speed capability
4
High-speed, B design Bearing series
bearings A
The assortment of super-precision bearings
Super-precision single row angular contact presented in this brochure includes two ISO
ball bearings in the S719 .. B (HB .. /S) and dimensions series:
S70 .. B (HX .. /S) series are designed for
high-speed operation and are best suited for • the extremely light 719 (HB) series
light load and low temperature operating • the light 70 (HX) series
conditions.
Features of B design bearings include: Bearings in both these series are suitable
for high-speed operation and tight radial
• asymmetrical inner and outer rings mounting space. If increased rigidity is re-
• a high number of very small balls quired, bearings in the 719 (HB) series are
• a lightweight phenolic resin cage used instead of bearings in the 70 (HX) ser-
• an optimized chamfer design ies, as they contain the greater number of
balls, relative to their bore size. Bearings in
The asymmetrical bearing rings enable the the 719 (HB) series also accommodate a
bearings to accommodate radial loads, and larger shaft diameter, relative to their out-
axial loads in one direction. The outer ring side diameter, when compared to bearings
shoulder-guided cage is designed to enable in the 70 (HX) series.
good lubricant supply to the ball/raceway
contact areas. The shape of the chamfer of
the inner and outer rings is optimized for
B design bearings for high-speed operation and
improved mounting accuracy. As a result, increased rigidity
mounting is not only facilitated, but there is
also less risk of damage to associated com-
ponents. When compared to other angular
contact ball bearings in the 719 and 70 ser-
ies, B design bearings have the greatest
possible number of very small balls for in-
creased rigidity.
A non-contact seal is fitted, standard, on
both sides of the bearing outer ring. The
seal forms an extremely narrow gap with
the cylindrical surface of the inner ring
shoulder.
When increased system rigidity is required,
bearings in the 719 (HB) series accommodate
a larger shaft diameter for a given outside
Optimized design of bearing ring chamfer to diameter, compared to bearings in the 70 (HX)
Non-contact seal for high-speed operation facilitate mounting series.
a°
r
1
b°
r
2
719 (HB) series 70 (HX) series
5
Bearing variants Contact angles
When compared to bearing arrangements
with open bearings and external seals, those Standard bearings are manufactured with
Based on the operating conditions in preci- with sealed bearings provide a number of the following contact angles:
sion applications, bearing requirements can advantages including:
vary. As a result, there are many variants of • a 15° contact angle, designation suffix
SKF super-precision angular contact ball • extended bearing service life CB (1)
bearings in the 719 .. B (HB) and 70 .. B (HX) • reduced need for maintenance • a 25° contact angle, designation suffix
series to choose from. • reduced inventory ACB (3)
Standard bearings are manufactured with • reduced risk of lubricant contamination
an integral seal fitted on both sides and filled during mounting and operation Bearings with an 18° contact angle, des-
with premium grease. As there is no friction ignation suffix FB (2), are available on
generated at the seal lip, the attainable Sealed bearings are identified by the desig- request.
speed of a sealed bearing is equivalent to nation prefix S (suffix /S). With three contact angles to choose from,
a comparably sized open bearing. designers can optimize their application
based on axial load, speed and rigidity
requirements.
Standard bearings are manufactured with an Three contact angles accommodate axial load,
integral seal fitted on both sides. speed and rigidity requirements.
15° 18° 25°
Sealed variant
The bearings are available in an all-steel and The bearings are available, standard, with seals
hybrid variant. but are also available in two open variants.
Steel balls Ceramic balls Open variant Open variant for
direct oil lubrication
6
Ball materials Open bearings Single bearings and
Standard bearings are available with: The bearings are also available without seals matched bearing sets A
for grease or oil lubrication in the 719 .. B
• steel balls, no designation suffix (HB) and 70 .. B (HX) series. To facilitate dir- SKF bearings in the S719 .. B (HB .. /S) and
• ceramic (bearing grade silicon nitride) ect oil lubrication, the outer ring of open S70 .. B (HX .. /S) series are available,
balls, designation suffix HC (/NS) bearings can also be manufactured with an standard, as:
annular groove and two lubrication holes as
As ceramic balls are considerably lighter and well as two annular grooves to accommo- • single bearings
harder than steel balls, hybrid bearings can date O-rings. This bearing variant is identi- • single, universally matchable bearings
provide a higher degree of rigidity and run fied by the designation suffix L (GH). • matched bearing sets
considerably faster than comparably sized • sets of universally matchable bearings
all-steel bearings. The lower weight of the
ceramic balls reduces the centrifugal forces
within the bearing and generates less heat.
Lower centrifugal forces are particularly
important in machine tool applications
where there are frequent rapid starts and
stops. Less heat generated by the bearing
means less energy consumption and longer
bearing and grease service life.
7
Applications
In the highly contaminated environment of
a machine tool spindle, one of the primary
causes of premature bearing failure is the
ingress of solid contaminants and/or cutting
fluid into the bearing cavity. To eliminate this
problem, the SKF assortment of sealed
super-precision angular contact ball bear-
ings in the S719 .. B (HB .. /S) and S70 .. B
(HX .. /S) series is an excellent solution. The
ability of the bearings to provide a high
degree of rigidity and accommodate high
speeds with extremely low runout provides
a variety of benefits for different
applications.
Applications Requirements Solution
• Electro-spindles • Efficient sealing against
• Metal cutting machines contaminants
• Woodworking machines • Low energy consumption
• Milling machines • Long service life
• Machining centres • Facilitated mounting
• Increased machine uptime
• High power density for
compact designs
• High positioning accuracy
SKF sealed super-precision angular contact ball
bearings in the S719 .. B (HB .. /S) and S70 .. B
(HX .. /S) series
8
A
9
Bearing selection
Bearing selection is paramount when deal- • A larger contact angle provides a higher
ing with applications that require a high degree of axial stiffness.
degree of accuracy at high speeds. The • When increased system rigidity is re-
many variants of SKF sealed super-precision quired, bearings in the 719 (HB) series
angular contact ball bearings are well suited accommodate a larger shaft diameter for
to accommodate the conditions dictated by a given outside diameter, compared to
these applications. bearings in the 70 (HX) series.
The main criteria when selecting bearings • Bearings mounted in a back-to-back
in the S719 .. B (HB .. /S) and S70 .. B arrangement provide the highest degree
(HX .. /S) series are: of rigidity.
• precision
Speed
• rigidity
• speed High-speed applications require cool-run-
• load ning, low-friction bearings like super-preci-
sion angular contact ball bearings.
When selecting bearings in the S719 .. B
Precision
(HB .. /S) and S70 .. B (HX .. /S) series, the
When dealing with rolling bearings, preci- following should be considered:
sion is described by tolerance classes for
running and dimensional accuracy. • Hybrid bearings can operate at higher
When selecting bearings in the S719 .. B speeds than comparably sized all-steel
(HB .. /S) and S70 .. B (HX .. /S) series, the bearings.
following should be considered: • As the contact angle increases, speed
capability decreases.
• All bearing variants are manufactured,
standard, to P4A (better than ABEC 7)
Load
tolerance class.
• All bearing variants can be manufactured In high-speed precision applications, the
to the higher precision PA9A (better than load carrying capacity of a bearing is typic-
ABEC 9) tolerance class, on request. ally less important than in general engineer-
ing applications. Angular contact ball bear-
ings can accommodate radial and axial loads
Rigidity
acting simultaneously. When these com-
In precision applications, the rigidity of the bined loads exist, the direction of the load
bearing arrangement is extremely import- also plays an important role in the selection
ant, as the magnitude of elastic deformation process.
under load determines the productivity and When selecting bearings in the S719 .. B
accuracy of the equipment. Although bear- (HB .. /S) and S70 .. B (HX .. /S) series, the
ing stiffness contributes to system rigidity, following should be considered:
there are other influencing factors such as
the number and position of the bearings. • The greater the contact angle, the higher
When selecting bearings in the S719 .. B the axial load carrying capacity of the
(HB .. /S) and S70 .. B (HX .. /S) series, the bearing.
following should be considered: • The axial load carrying capacity of a
bearing arrangement can be increased
• Ceramic (silicon nitride) balls provide a by adding bearings mounted in tandem.
higher degree of stiffness than steel balls.
10