Transcript Hi Roll Bearings

UBC Bearings of America Limited
basic
BEARING
knowledge
What is a Bearing Used for?
Designed to:
l Reduce friction
l Carry loads
l Guide moving parts
Rolling and Sliding Friction
µ
µ
Component parts of a ball bearing
Seal
Rolling elements
Outer ring
Inner ring
Cage
Seal
Seal and Shield Variations
Shields
-Z and -2Z
Contaminant
exclusion
Low-friction seals
Seals
-RZ and -2RZ
-RS and -2RS
Silent
running
Grease
retention
Speed
capability
Characteristics of Different Seals
Application
Shield
Seal
Need
2Z
2RZ
2RS
Low friction
torque
+++
++(+)
–
High speed
ability
+++
++(+)
–
Grease
retention
+
++
+++
Dust
exclusion
+
++
+++
Water
exclusion
–
–
+
Low/high
operating
temperature
+++ Excellent
Depends on:
Depends on:
Grease
– Grease
– Rubber mix
++ Good
+ Fair
– Poor
Storage Requirements
Roller and Ball Raceway Contact
Axial and Radial load capability
Radial load
Fr
Axial load
Fa
Combined load
Roller Types
Ball
Spherical roller
(symmetrical)
Spherical roller
(asymmetrical)
Taper roller
Cylindrical roller
Needle roller
Ball and Roller Bearing Ranges
+ Roller bearings
Ball bearings
Deep groove Angular
contact
Self-aligning
Cylindrical
Taper
Spherical
Load Capabilities
Load carrying capacity
is expressed as the basic
dynamic load rating
Ball Bearing Capabilities
Deep groove
Angular contact
Self-aligning
Radial load
Axial load
Speed
Accommodates
carrying capacity
carrying capacity
capability
misalignment
Function of the Cage
l
Prevent immediate contact between
rolling elements to minimize friction
and heat generation
l
Guide the rolling elements
l
Provide space for lubricant
l
Retain the rolling elements when
bearings of separable design
are mounted or dismounted
Cage Variants
Nylon cage
Steel cage
Solid brass cage
Nylon Cages
+
Lightweight
+
High elasticity
+
Good sliding properties
+
Good marginal
lubrication properties
–
Operating temperature
< +120 °C
Steel Cages
+
Lightweight
+
High strength
+
No operating
temperature limit
+
High vibration and
acceleration resistance
–
Sensitive to
poor lubrication
Solid Brass Cages
+
Very high strength
+
Very high vibration and
acceleration resistance
+
Suitable for very high
speed in connection
with circulating oil
–
Relatively (very)
expensive
Internal Clearances
Radial
clearance
Axial
clearance
The bearing internal clearance is defined
as the total distance through which one
bearing ring can be moved relative to the
other under zero measuring load.
Why Internal clearance?
• In order to fit a bearing tightly on a shaft, it is necessary
that the shaft is slightly larger than the bore of the inner
ring. When the bearing is mounted, the inner ring will
be expanded and consequently the space available for
the rolling elements will be reduced. The reduction in
space available for rolling elements when the bearing is
mounted is accommodated by the internal clearance.
Why Internal clearance?
• Steel will expand with increased temperature. In
operation, the temperature of the various parts of a
bearing will not remain uniform and resulting in
varying degrees of expansion which is compensated
by the internal clearance.
Internal Radial Clearance
COLD
Reduced
radial
clearance
Compression
Expansion
Clearance range
C1 Clearance less than C2
C2 Clearance less than Normal
C3 Clearance greater than Normal
C4 Clearance greater than C3
C5 Clearance greater than C4
WARM
The internal clearance required is
dependent upon the mounting fit and
the operating conditions. In case of
doubt, a bearing with greater internal
clearance shall always be selected.
Effect of Internal Preload and Clearance on
Bearing Life
Relative basic rating life L10, %
Preloading
Clearance
Correct Fits
Tolerance range for bearings
manufactured to ISO
Bearing Selection Factors
Available space
Speed
Load/Direction
Misalignment
Life
Operating conditions
ISO Standards
ISO
International
Organization for
Standardization
Diameter Series
Relationship: Diameter and Width Series
Diameter Series
Width Series
Height Series
Diameter Series
Dimension Series
Width Series
Bore designation system
Bore diameter
Written as
Example
Below 10 mm
3
.
.
9
3
.
.
9
623
.
.
629
10 – 17 mm
10
12
15
17
00
01
02
03
6200
6201
6202
6203
20 – 480 mm
20
25
.
.
480
04
05
.
.
96
6204
6205
.
.
61896
Above 500 mm
710
/710
241/710
How the Designation System Works
Bearing types
Radial bearings, width (B, T)
Thrust bearing, height (H)
Outside diameter (D)
Bearing size d/5
(30 mm bore diameter)
Tapered Bore Suffixes
Suffix K
Taper 1:12
Suffix K30
Taper 1:30
Deep groove ball bearing
Self-aligning ball bearing
Plane thrust ball bearing
Angular contact ball bearing
Spherical roller bearing
Taper roller bearing
Cylindrical roller bearing
THE END