Anti-friction bearings Flashcards
The ____________ capacity of anti-friction bearings is dependent on the area of contact between the rolling elements and the raceway.
load capacity
True or false:
The load capacity of a bearing can be increased by adding rolling elements to the bearing.
true
What is the angularity of bearings?
misalignment;
the shaft is centred in the bearing, but positioned at an angle to the bearing axis
What happens to deep groove ball bearings when subjected to angularity?
the raceways will pinch the ball, causing overload and failure
True or false:
Cylindrical roller bearings handle misalignment better than deep groove ball bearings.
false;
the tolerate less angularity
Why is it generally accepted that the larger the anti-friction bearing, the slower the top speed?
the weight of the rolling elements;
the larger the bearing, the larger the elements, the more mass that is spun
If the nominal contact angle is 0º, and the load carries at 90º to the shaft axis and the bearing is a(n) ____________ load bearing.
radial
If the nominal contact angle is 90º, and the load is in line with shaft axis, the bearing is a(n) ______________ load bearing.
axial
If the nominal contact angle is between 0º and 90º, then the load acts at an angle to the shaft and the bearing is a(n) _______________ load bearing.
combination;
both radial and axial
What changes the angle of the loaded zone in an anti-friction bearing?
the amount of internal clearance and preload
What is the function of a raceway in a bearing?
to provide a smooth surface for the rolling elements to move on
True or false:
The rolling element shape is a major factor for the speed and load capacity of a bearing.
true
What is the angle of loaded zone on a roller thrust bearing?
360º
Which rolling element design allows for the greatest amount of shaft angularity?
spherical
What type of contact does a ball have with the raceway of a bearing?
point contact
What type of contact does a spherical or cylindrical roller have with the raceway of a bearing?
line contact
What are the 2 main classifications of anti-friction bearings?
- ball
- roller
What are the 4 variations of anti-friction roller bearings?
- cylindrical
- needle
- tapered
- spherical
What is the first digit on the ISO code for a single row deep groove ball bearing?
6
This type of roller bearing is a general purpose bearing and is used more widely than any other type of bearing.
single row deep groove ball bearing
True or false:
Single row deep groove ball bearings are classed as a combination load bearing, since it can support moderate axial loads.
false;
they are classed as a radial load bearing
What does a Conrad bearing refer to?
A deep groove ball bearing
Conrad created the method used to load the balls into the bearing as it is being assembled
- done by compressing the outer ring enough to bulge enough to allow the balls to be loaded
** ball bearings only
What is the first digit of the ISO bearing code of a maximum capacity deep groove ball bearing
6
- usually omitted
What physical feature can be used to identify a deep groove ball bearing is a maximum capacity bearing?
the loading slots machined into the inner and outer raceways
What is the main benefit of a maximum capacity deep groove ball bearing when compared to a normal deep groove ball bearing?
high radial load capacity
What are the 2 main limitations of a maximum capacity deep groove ball bearing when compared to a normal deep groove ball bearing?
- less axial load capacity
- more sensitive to misalignment
What is the first digit on the ISO code of a double row deep groove ball bearing?
4
What is the main design advantage of a double row deep groove ball bearing when compared to a normal deep groove ball bearing?
higher radial load without increasing the radial dimension
What is the first digit on the ISO code of a double row internally self-aligning ball bearing?
1
What is the first digit on the ISO code for an externally self-aligning ball bearing?
none;
these are usually sized in inch series
This type of ball bearing is designed to accommodate angular misalignment in mounting.
externally self-aligning ball bearings
- think pillow block
What is the first digit on the ISO code for a single row angular contact ball bearing?
7
This type of ball bearing can support substantial thrust loads in a single direction and must operate with an axial load component (ideally, a combination).
single row angular contact ball bearing
With a single row angular contact ball bearing, the thrust load must be against the ___________ shoulder on both races.
high
What is the first digit on the ISO bearing code for a double row angular contact ball bearing?
0
What kinds of loads can a double row angular contact ball bearing accommodate?
heavy radial and axial loads
Double row angular contact ball bearings cannot tolerate any misalignment. Why is this?
the misalignment alters the load distribution between the two rings
What types of loads can a single row angular contact ball bearing not operate with?
purely radial loads
What is the first digit on the ISO bearing code for a four-point angular contact ball bearing?
QJ
True or false:
A four-point angular contact ball bearing is considered a high capacity bearing.
true
- the split allows for additional balls to be placed in the raceway
What types of loads can a four-point angular contact ball bearing accommodate?
axial or combination;
- it cannot handle a purely radial load because of the split along the inner race
What type of load can a four-point angular contact ball bearing not handle?
purely radial
True or false:
Four-point angular contact ball bearings can handle reversing thrust loads.
true
What is the first digit on the ISO bearing code for a ball thrust bearing?
5
What is the speed limit of a ball thrust bearing when compared to a radial load bearing of the same size?
about half the speed
What are the 4 common shapes of roller bearings?
- cylindrical
- needle
- tapered
- spherical
What does it mean when a bearing has the ability to displace?
the rolling elements can move axially in the bearing raceway
What is the first digit on the ISO bearing code for single row cylindrical roller radial load bearings?
N
What is the first digit on the ISO bearing code for a cylindrical roller thrust bearing?
8
What can happen if cylindrical thrust roller bearings travel too quickly?
the inside and outside diameter of the rollers travel at different speeds, causing skidding on one part of the roller if they travel too fast
What are 3 common types of needle bearings?
- no cage or inner ring
- drawn steel cup and no inner ring
- machined inner and outer rings
In bearings, what is the relationship between friction and speed?
friction up = speed down
- the more friction in a bearing, the slower the top speed
This type of needle bearing is restricted to slow speeds or oscillating motions since the rollers rub against each other.
no cage or inner ring needle bearing
What is the inner ring of an anti-friction bearing?
The ring that sits on a shaft when mounted
With an anti-friction bearing, which ring would sit in a housing?
The outer ring
With an anti-friction bearing, the surface on which the rolling members roll on is called the:
Raceway
This component of an anti-friction bearing supports the load and ideally should roll (not slide, skid, or drag).
The rolling elements
What component of an anti-friction bearing separates the rolling elements from each other?
The cage
What are the 3 functions of the cage in an anti-friction roller bearing?
- Prevents rolling elements from rubbing against each other
- Pushes the rolling elements through the unloaded zone
- Guide the rolling elements with minimal amount of friction
Identify the following bearing type and the first digit of its design code:
Four-point angular contact ball bearing
First digit of ISO design code: QJ
Identify the following bearing type and the first digit of its design code:
Double row internally self-aligning ball bearing
First digit of ISO design code: 1
Identify the following bearing type and the first digit of its design code:
Single direction ball thrust bearing
First digit of ISO design code: 5
Identify the following bearing type and its design code:
Single direction external self-aligning ball thrust bearing
ISO design code: 5
Which type of ball thrust bearing can correct for some misalignment?
Single direction external self-aligning ball thrust bear
Identify the following bearing type and the first digit of its design code:
Double direction ball thrust bearing
First digit of ISO design code: 5
Identify the following bearing type and the first digit of its design code:
Single row angular contact ball bearing
First digit of ISO design code: 7
Identify the following bearing type and its design code:
Single row deep groove ball bearing
ISO design code: 6
Identify the following bearing type and the first digit of its design code:
Double row deep groove ball bearing
First digit of ISO code: 4
Identify the following bearing type and its design code:
Tapered roller bearing
ISO design code: 3
- ISO code may not be reliable, as often they will be an inch series bearing
Identify the following bearing type and its design code:
CARB bearing
ISO design code: C
Identify the following bearing type and its design code:
Spherical roller bearing
ISO design code: 2
Identify the following bearing type and its design code:
Drawn steel cup and no inner ring needle bearing
ISO design code: none; manufacturer nomenclature
Identify the following bearing type and its design code:
No cage or inner ring needle bearing
ISO design code: none; manufacturer nomenclature
Identify the following bearing type and its design code:
Machined inner and outer rings needle bearing
ISO design code: none; manufacturer nomenclature
Identify the following bearing type and its design code:
Cylindrical roller bearing
ISO design code: N
Identify the following bearing type and the first digit of its design code:
Cylindrical roller thrust bearing
First digit of ISO design code: 8
Identify the following bearing type and the first digit of its design code:
Maximum capacity deep groove ball bearing
First digit of ISO design code: 6 (often omitted)
This type of needle bearing must be fitted to a smooth, accurately machine housing and depends on the bore for support and its shape.
drawn steel cup and no inner ring needle bearing
Needle bearings are similar to cylindrical rollers, except that they are ________ to ________ times as long as their diameter.
2.5 to 10 times
Why do needle bearings have a high capacity?
their extended length (long contact area)
What type of bearing would be used where the was very little radial space?
a needle bearing
On a single row tapered roller bearing, the inner ring is called the 1.__________ and the outer ring is called the 2.__________.
- cone
- cup
With a tapered roller bearing, the cage, cone, and roller combine to form one assembly, called the:
cone assembly
What are the 3 functions of the cage in a tapered roller bearing?
- space the rollers so they don’t rub against each other
- align the rollers
- push the roller through the unleaded zone
Can a tapered roller bearing be used to support a purely radial load?
no
How are the internal axial and radial clearances set on a tapered roller bearing?
by moving the cup and cone axially closer or further apart
What are the 2 types of cages found on tapered roller bearings?
- pressed steel cage
- pin cage
This type of tapered roller bearing cage allows closer roller spacing for more rollers with rolling elements that are usually hollow.
pin cage
Identify the following double row tapered roller bearing arrangement:
Face-to-face arrangement
(Thin to thin)
Identify the following double row tapered roller bearing arrangement:
Back-to-back arrangement
(Thick to thick)
True or false:
Double row taper roller bearings are matched pre-set assemblies, and are not interchangeable.
true
A double row taper roller bearing with a face-to-face assembly is also known as:
a double cone assembly
A double row taper roller bearing with a back-to-back assembly is also known as:
a double cup assembly
Which type of double row taper roller bearing requires the use of a cone spacer?
the double cup assembly
True or false:
The single row design of a spherical roller bearing has very high axial thrust capacity but very little radial thrust capacity.
false;
it has very high radial and very low axial
Which double row taper roller bearing arrangement is more rigid: back-to-back or face-to-face?
back-to-back
This type of bearing is radially compact like a needle bearing but has some misalignment capacity of a spherical roller bearing.
CARB bearing
What does CARB bearing stand for?
compact aligning roller bearings
This type of bearing handles more axial displacement than any other type of bearing.
CARB
How much displacement can a CARB bearing handle?
up to 20% of the bearing width
What is the ISO design code for a double row cylindrical roller bearing?
NNU
ISO bearing standards apply to what 3 components of a bearing?
- bearing type
- boundary dimensions
- some additional features (not all)
What kind of bearing will have a 4 digit ISO code?
a ball bearing
- because a sphere only has one measurement value
On a 5 digit ISO bearing code, X21XX, what do the second and third digit represent?
the dimension code
2 = width
1 = OD
On a 5 digit ISO bearing code, XXX08, what do the last two digits refer to?
the nominal bearing bore
- in this case you take 08 and multiply by 5
For and ISO bearing code of a bearing over _________mm, the actual diameter of the bearing is often given after a backslash (/).
500mm
What size bore would a bearing have if the ISO dimensioning series was 00?
10mm
What size bore would a bearing have if the ISO dimensioning series was 01?
12mm
What size bore would a bearing have if the ISO dimensioning series was 02?
15mm
What size bore would a bearing have if the ISO dimensions series was 03?
17mm
What does C indicate on an ISO bearing code suffix?
clearance
C1 to C5, with CN for normal
Which ISO bearing code clearance is the tightest?
C1
Which ISO bearing code clearance is the loosest?
C5
What ISO bearing code refers to normal clearance?
CN
*often not included on the bearing
Where does CN fall on the ISO bearing code clearance scale?
between C2 and C3
C2.5
What does K designate on an ISO bearing code?
taper;
K = 1:12 taper
What does K30 designate on an ISO bearing code?
taper;
K30 = 1:30 taper
What does RS designate on an ISO bearing code?
intergral rubbing seal
What does Z designate on an ISO bearing code?
intergral shield
What are 4 common types of linear anti-friction bearings?
- ball bushing
- linear ball or roller
- caged needle
- cam follower
Which type of bearing shield can handle faster speeds: RS or Z?
Z
This type of linear ball bearing is made up a sleeve with pockets on the inside for a ball to sit in.
ball bushing
- Is a linear ball bushing a recirculating or non-circulating bearing?
- What does the above mean?
- non-circulating
- the balls are always in contact with the shaft and bushing pocket
- What is a recirculating linear ball bearing?
- What issue does this design overcome?
- a bearing where the balls travel along a groove track that allows a new ball to replace one that has rolled out of the way
- that the ball is travelling at a slower speed than the surface it touches, which will cause the ball to fall behind
True or false:
Linear or roller bearings can run on a flat, triangular, or rectangular shaped track.
true
The ______________ is the moving component that carries the load in a linear ball bearing assembly.
carriage
What is the main advantage of the caged needle linear roller bearing?
it has a high load capacity
The term _________ commonly describes an eccentric designed wheel or lobe shape.
cam
True or false:
The correct fit of a bearing ensures that the rings do not spin in their seats.
true
What 2 things can happen to the rolling elements if there is not proper fit between an anti-friction bearing and the housing/shaft?
- the elements can bind (too little clearance)
- the elements can skid in the raceway (too much clearance)
The _______________ for any dimension is the total permissible variation in its size.
tolerance
_________ is the term for the range of permissible tightness or looseness of mating parts.
Fit
What are the 3 types of fit?
- clearance
- transition
- interference
A(n) ______________ fit results in a shaft that is always smaller than the bearing bore or the bearing is always smaller than the housing bore.
clearance
A(n) _______________ fit results in a shaft and bore sizes that the combination of their tolerances can produce a tight fit, a loose fit, or something they are the same size.
transition
A(n) _______________ fit results in a shaft that is larger than the bearing bore or that the outside diameter of the bearing is larger than the housing bore.
interference
What does an upper case letter in a tolerance code indicate?
tolerance for a hole size (housing bore)
What does a lower case letter in a tolerance code indicate?
tolerance of the shaft
What is the tolerance position of a tolerance code?
whether the tolerances result in a clearance, transition, or interference fit
What 3 pieces of information are required to interpret fit tables?
- operating conditions
- bearing type and size
- type of ring loading
What are the 3 types of ring loading?
- rotating load
- stationary load
- indeterminate load
What is the most common type of ring loading?
stationary load
This type of ring loading occurs when the load is stationary and the ring it acts on is rotating, such as on the outer ring of the bearings inside a conveyor roller.
rotating load
This type of ring loading occurs when the ring is stationary and the load rotates, such as on the inner ring of the connecting rod bearings in a roller bearing crank case.
rotating load
True or false:
The ring with a rotating load requires an interference fit.
true
This type of ring loading occurs when the load and the ring it acts on are both stationary, such as a bearing supporting the weight of the rotor in an electric motor.
stationary load
This type of ring loading occurs when the load and the ring both rotate together, such as on the outer ring of the bearings on a roller bearing crank.
stationary load
True or false:
A ring subject to a stationary load has a looser fit than for the rotating ring load unless the direction of the load varies.
true
This type of ring loading occurs when the direction of the load might reverse at any time.
indeterminate loading
What type of fit does an indeterminate ring load require?
interference or transition on both rings
On an fit code, what does the letter L mean?
loose
- clearance fit
On an fit code, what does the letter T mean?
tight
- interference fit
What feature on linear anti-friction bearings is used to increase the efficiency by reducing sliding friction?
recirculation of the balls or rollers
True or false:
If a compact aligning roller bearing is subject to a thrust load, it prevents that load from moving the shaft axially.
false;
- it allows for some displacement.
What is another name for a cam follower linear bearing?
track roller
Why are the rollers in a spherical roller bearing shaped like barrels?
to allow angularity on the inner ring
What type of linear anti-friction bearing is made in modular lengths so it can be assembled to meet the requirements of the machine?
caged needle
True or false:
The components of a double row taper roller bearing are interchangeable with another bearing of the same type as long as they are from the same manufacturer.
false
Which type of single row angular contact ball bearing and tapered roller bearing arrangements handle reversing axial loads?
face-to-face and back-to-back arrangements
Which type of single row angular contact ball bearing and tapered roller bearing arrangements handle the most radial load but handles axial load in the direction towards the high should on the outer ring?
tandem arrangements
Which type of single row angular contact ball bearing and tapered roller bearing arrangements handle is the most rigid?
back-to-back
What is the purpose of preloading a bearing arrangement that supports either side of a shaft, such as a gearbox?
to prevent any axial movement of the shaft
What two types of bearings are used in arrangements that require preload?
- tapered roller bearing
- angular contact ball bearings
Which type of bearing is used as the floating bearing in a fixed and floating arrangement?
single row cylindrical roller radial roller bearing
ISO Code N
True or false:
Anti-friction roller bearings use the principle of elasto-hydrodynamic lubrication
true
This type of bearing has no integral seals.
open bearing
True or false:
Integral seal or shield bearings have grease installed in the bearing during manufacturing.
true
What is an oil slinger?
a disc attached to the shaft that rotates with the shaft and splashes oil onto the bearing
True or false:
An oil slinger is considered a splash type lubrication system.
true
What is another name for an oil slinger?
an oil thrower
This type of mechanical oil system consist of a partially submerged ring that rest atop the shaft.
oil pick-up ring
True or false:
Grease retains contaminants.
true
True or false:
Grease acts as a better sealant than oil.
true
How frequently does a sealed bearing require re-lubrication?
never;
it’s sealed, so no new grease can enter
Why are oil pick-up rings often made from bronze?
it does not corrode and softer than the shaft material (sacrificial)
An increase in the loaded zone results in the load being distributed over more rolling elements. How can this be achieved?
by reducing the internal clearance through preload
What are 3 types of specialty bearings?
- ceramic
- cartridge
- split ring
If a bearing is likely to encounter moisture, what materials should it be made from?
stainless steel and brass
How are bearings made so they are quieter than standard bearings?
with closer tolerances
This type of full fill hydrodynamic lubrication is where high loads on small surface areas or high speeds cause the lubricant viscosity to increase to a point where it is almost solid. This causes the surfaces applying the force on the fluid to slightly deform and the layer of lubricant to maintain a thickness of 0.25 to 3 microns.
elasto-hydrodynamic lubrication
Identify the following linear roller bearing:
Flat ball cage linear bearing
Identify the following roller bearing:
Caged needle linear bearing
Identify the following fits:
A = clearance
B = transition
C = interference
Identify the following types of ring loading:
A = rotating load
B = stationary load
C = indeterminate load
Identify the following single row angular contact ball bearing arrangement:
Face-to-face
Identify the following single row angular contact ball arrangement:
Back-to-back
Identify the following single row angular contact ball bearing arrangement:
Tandem
What is the benefit of an internally self-aligning ball bearing?
It accommodates misalignment due to shaft deflection (“wobble”)
What is the benefit of an externally self-aligning ball bearing?
It accommodates misalignment in the mounting arrangement
What must cylindrical roller bearings be equipped with to prevent displacement?
an angled ring
True or false:
Cylindrical roller bearings that are separable in both directions are able to displace when subject to axial loads.
true
What feature of ball thrust bearings (and most roller thrust bearings in general) limits their maximum speed to about half that of a radial bearing?
the centrifugal force spins the balls out of the raceways
- in these types of bearings, it is the cage that holds the elements from leaving due to centrifugal force, while with radial bearings it is the raceway.
