Anti Friction Bearings Flashcards
Three advantages of anti friction bearings are: (3)
- Versatility
- Low friction
- Can be packed to avoid frequent lubrication
The basic parts of an anti friction bearing are: (3)
- Two hardened steel rings (races)
- Hardened balls or rollers (rolling elements)
- separator
If there is no inner ring, the bearings fit directly on the:
Hardened shaft
Bearings may have other parts, such as a snap ring to set:
axial location
Rolling elements are classified into these 3 basic styles: (3)
- Ball
- Roller
- Needle
Roller bearings can be sub-divided into these 3 styles: (3)
- Cylindrical
- Tapered
- Spherical
Ball bearings can be used as a guide for axial shaft measurement using:
recirculating ball bushings
Many bearings use shields and seals to prevent:
Unwanted material from entering the housing
Regarding seals, you would use this type of bearing when lubricant is expected to work through the bearing from one side to the other
Open bearing
Regarding seals, you would use this type of bearing when you want solids kept out but not fluids
Shielded bearing
Regarding seals, you would use this type of bearing when you want both solids and fluids kept out
sealed bearing
Regarding seals, you would use this type of bearing when conditions are very dirty and abrasive
Shielded and sealed bearing
Ball bearings have a low to ____ load capacity
medium
roller bearings usually have a low to ____ load capacity
high
What are the three types of loads that can be applied to anti friction bearings? (3)
- Radial load
- Thrust (axial) load
- Combination radial thrust load (aka angular load)
Ball bearings are generally suited to high speed applications, up to ______ RPM
40, 000 RPM
Roller bearings are generally suited to lower speed applications, up to _____ RPM
20, 000 RPM
Normal range is 2000-20 000 RPM
As the load capacity of a bearing increases, the bore stays the same, but:
The outer diameter increases and the width and thickness of the rings increases
Regarding bearing service weight, 00 refers to:
Ultra light
Regarding bearing service weight, 100 refers to:
Extra light
Regarding bearing service weight, 200 refers to:
Light
Regarding bearing service weight, 300 refers to:
Medium
Regarding bearing service weight, 400 refers to:
Heavy duty
Roller bearings may have either a _____ or _____ bore
straight or tapered
The bearing bore size is indicated by the _______ digits of the bearing number
last two
From 20mm to 480mm, the bearing bore diameter is is found by multiplying the last two digits of the bearing number by:
5
Above 480mm, the bearing bore diameter is
directly included in the bearing number
a non separable bearing is one that:
cannot be separated easily
a separable bearing is one that:
can easily be taken apart
non aligning bearings are used in machines where:
bearings are held in alignment by the bores in the housing
self aligning bearings may be internal or external. In an internal self aligning bearing, the inside of the outer ring is:
concave
self aligning bearings may be internal or external. In an external self aligning bearing, the outside of the outer ring is:
convex
Most bearing codes give 3 pieces of information: (3)
- Type of rolling element
- Service weight
- Diameter of bore in mm
in most cases, the orientation of a bearing won’t matter, but it’s good practice to face the bearing code numbers towards the end of the shaft because:
It’s easier and quicker to identify the bearing
On a bearing code, the letter K identifies:
A tapered bore, 1:12 taper
Initial clearance is the:
Clearance in a bearing before it is installed on the shaft
Installed clearance is the clearance left in the bearing after installing it, or:
Or the clearance left in a taper bore bearing that has been forced up the taper
Running clearance is the:
Clearance left in a bearing when the machine is at operating temperature and has lubricant supplied
Bearings may have one of two fits: (2)
- Push fit
- Interference fit
Be careful when using an emery cloth to improve the shaft surface, be careful to:
Not remove interference deliberately machined in the shaft
When installing a bearing, after checking a shaft, wipe it clean and coat it with a light oil. With a press fit, you may need to use a:
Anti seize compound
Push fit means:
Bearing is installed by hand without mechanical aids
Used when the bearing is held in place by mechanical aids, such as snap rings
___ is the very slow rotation of a push fit bearing race. One rotation of the ring is equal to several million revolutions of the rest of the bearing.
Creep
Creep changes the contact area on a raceway and:
Extends the life of the bearing
The amount of interference in the shaft and bearing ring is exactly equal to the______ in the bearings after installation
Clearance reduction
To achieve interference fits, bearings can be installed using: (2)
- Press or shrink fits
- Tapered adapter sleeve
In regards to bearing fits, the usual bearing installation has:
One ring interference fit, one ring push fit
On a straight bore bearing, which bearing ring has the press fit?
Rotating ring
Non rotating is a push fit
Press fits are common on small bore bearings. To press fit a bearing, use a ____ to distribute force evenly
tube
When pressing a bearing onto a shaft, ensure it is square to the shaft, and apply a light coat of:
oil to reduce friction
As you press a bearing onto a shaft, rotate the outer ring by hand to check:
Clearance. If clearance is lost, do not press the bearing the rest of the way
When pressing a shaft through a bearing, ensure your support blocks touch:
Both the inner and outer races, but most importantly, the inner race,
When heating a bearing, it is usually heated to ____ °C above ambient temperatures
45-50C
Note: No higher than 120C
To chill a bearing, you can use: (2)
- Liquid air
- Dry ice and alcohol
To heat a bearing, some common methods are to use: (4)
- Heat lamps
- Oven
- Induction heater
- Oil bath
____ method of heating a bearing is slow and can be used for small bearings.
heat lamp
____ method of heating a bearing is relatively safe, as the temperature can be controlled
Oven
____ method of heating a bearing is quick and quiet. Temperatures are monitored with a wax crayon or by measuring the bore
Induction heater
When using _____ method of heating a bearing, it is important to remember to keep the bearings suspended with wire
oil bath
When installing a hot bearing on a shaft, move it:
quickly to its final position
Press or shrink fitting will reduce the:
Internal clearance on the bearing.
A replacement bearing such as a tapered roller or angular contact bearing has the end float controlled by:
shims
An outer ring can be installed in either a bored (solid, one piece) housing or a:
split housing
Positive keeping is to:
use a device to hold position
In tapered roller bearings, the inner race is called the:
cone
In tapered roller bearings, the outer race is called the:
Cup
The end caps on a bearing can be used for:
positive positioning (axial)
note: can be with or without shims
To prevent end float:
One bearing on any assembly should be fixed axially in the housing
Note: called the held or fixed bearing
It is generally better to locate the fixed bearing on the:
drive end of the shaft
A bearing that is not fixed axially is called a:
Free or floating bearing
Having floating bearings allows:
the shaft to expand and contract
The floating bearing is usually where within the pillow block?
center, never up against a shoulder
Tapered roller and angular contact bearings are mounted so the end float of a shaft between two bearings is:
held to a required minimum
Thrust adjustment on a bearing may be made in two ways. When the outer race, or cup, is fixed in the housing:
adjust the inner race or cone
Thrust adjustment on a bearing may be made in two ways. When the inner race, or cone, is fixed on the shaft:
adjust the outer race or cup
In most applications, the outer race is adjusted by means of:
end cover and shims
Angular contact bearings are bought and installed as a matched pair. What are the three basic arrangements? (3)
- Back to back
- Face to face
- Tandem
Note: which one you use depends on load, speed, direction and the amount of thrust
The use of a tapered sleeve adapter allows you to:
mount bearings at any place along a standard shaft
When tapered adapter mountings are used, take care that the bearing is not tight internally, because:
the clearance will be eliminated
What is being described?
- Swivel the outer race while tightening
- you will feel light drag when clearance is reduced
- stop tightening at this point and lock in place
mounting ball bearings with a tapered adapter sleeve
Note: the general procedure
Dismounting a bearing hydraulically gives a:
Abrupt release
When installing tapered bore spherical roller bearings, the most practical method for checking clearance is to:
use feeler gauges
When mounting tapered bore bearings, it can be helpful to oil:
Outside and threads of the sleeve
You can assemble smaller tapered bore bearings with the tab washer in position, but it is not recommended for larger bore bearings because:
you could shear the tab
when mounting tapered bore spherical roller bearings, you should tighten the adapter nut with a spanner wrench until it is snug. Drive against the nut with a hammer and soft steel bar, tighten, check for clearance, repeat drive/tighten, until :
final clearance is reached.
For standard clearance, spherical roller bearings where no tables are available, a rule of thumb is to reduce the initial clearance by roughly:
50%
note: another rule of thumb is to convert the last two digits of a bearing number into thousandths of an inch and reduce the bearing clearance by that much.
The best way to pull off a bearing with a minimum amount of damage to the bearing or shaft is with a: (2)
- press
- pullers
When pressing a bearing off a shaft, ensure that:
no load goes through the rolling elements. Press on inner race.
When removing a bearing from a shaft, if you need to pull on the outer race, you should:
Guard the outer ring to prevent injury from debris if the bearing explodes/fractures
Note: especially important when hydraulically pulling
You can remove bearing cups from a housing with a:
Cup puller aka Inside puller
The big differences in a withdrawal sleeve vs an adapter sleeve is the withdrawal sleeve: (3)
- Used in a solid bored housing
- Sleeve slides under the bearing
- Bearing is held by a shoulder against inner ring
When installing a withdrawal sleeve, the installation order is bearing then sleeve. When installing an adapter sleeve, the order is:
Sleeve then bearing
Both the adapter sleeve and the withdrawal sleeve use the same routines to check the:
Initial clearance
The tool used to remove a tapered withdrawal sleeve is called a:
Withdrawal nut
Bearing cups are frequently set in seats with no room to use a set of pullers. In such a case, the cup can be removed by:
Welding a bead on the face of the raceway. This will shrink the race as it cools
Hydraulic dismounting (removal) uses the force developed by the oil or grease pressure to:
expand the inner ring of the bearing
For hydraulic dismounting, oil injection can be done with: (2)
- Grease gun (capable of developing 1000PSI)
- Hand operated pump for a portable jack (using SAE 40 or heavier oil)
When hydraulically dismounting a bearing from a tapered sleeve, what should you do to ensure safety?
Leave the locknut on the threads and keep it close to the bearing. The press fit will be immediately and abruptly released.
Pillow blocks come in two main groups: (2)
- One piece
- Split
One piece pillow block housings are pre assembled. The unit is slipped over a smooth shaft and bolted into position. Common designs are: (3)
- Single groove ball bearings
- double taper roller bearings
- spherical or concave rollers
Note: these bearings are externally self aligning. Shape of the outer ring rocks/pivots in the housing.
Two common methods of securing a one piece bearing housing to a shaft are: (2)
- Eccentric collar
- two set screws
A pillow block is mounted with its base:
Parallel to the shaft
When mounting pillow blocks with one piece housings, tighten them on the base before:
locking the inner ring in position on the shaft.
Note: allows the bearing to align to the shaft
A flange bearing has its base at:
90° to the shaft
The inner/outer rings and rolling elements of flange bearings are easily replaceable and supplied as one unit called a:
cartridge
One common type of needle bearing has no separators or inner ring only an outer ring and rolling elements. To keep the the needles in place before mounting, the bearing is fitted with a:
temporary sleeve
Note: it is possible to coat smaller roller bearings in grease so they stay in position while installing
Thrust bearings, because of centrifugal force, are limited in:
The speed they can be used at
Tread bearings with one side shielded like:
bearings without a shield
Do not wash bearings with seals on both sides, instead:
wipe them with a clean rag
Note: to prevent dirt from working inside
When washing a bearing in solvent, use two washes. Do the second wash in:
clean solvent
When using an air hose to clean a bearing, don’t:
spin the bearing.
Some solvents remove all traces of lube, leaving a dry bearing, which can do what when checking for wear?
give false readings
When storing bearings, coat them lightly in oil. Store them in a special, :
acid free bearing wrapper (oil impregnated paper)
Store bearings in a clean, dry place until needed, away from:
vibrations
What are 3 symptoms of bearing failure: (3)
- Temperature rise
- Increased vibration
- Unusual noise
The most common cause of anti-friction bearing failure is:
contamination
Fill a housing 1/3 to 1/2 with grease. For oil lubrication, fill the case up to:
halfway up the lowest rolling element
Cooper bearings are:
Split bearings, used where bearing location is not easily accessible.
