Types of Shaft Keys:
Definition, Use, Function,
Advantages & Disadvantages
Shaft Keys
What is Shaft Key?
Types of Shaft Keys: Definition, Use, Function, Advantages &
Disadvantages :- Shaft key can be defined as the piece of metal
which is used for connecting the rotating machine element with
shaft. It is generally used for the prevention of relative rotation
between two parts and they are able in transmission of torque to
take place. The rotating element (such as pulley, gear) and the
shaft should have a key seat and a keyway for the proper
functioning of a shaft key. A pre-cut slot is present in shaft in
which one part of shaft key can fit and the other part of shaft key
fit into a keyway which is a slot provided in the hub. The overall
system is known as keyed joint and is able to provide relative
axial movement between two parts.
Shaft key can be made up of a number of materials, most
commonly from steel. These keys are also available in various
shapes and sizes. Tapered or rectangular are the most common
shape of shaft key.
They keyway which is a slot provided in hub of a gear,
sprocket, pulley and various rotating power devices which can
receive key. The slot in hub is cut on key seating machines
by milling, shaping, broaching, slotting and planning.
The overall system which is called as keyed joint is a essential
part of elements which can transmit mechanical power where
they ensure connection is transmitting the power, load and
rotation in accuracy without slipping according to the design
requirement.
Types of Shaft Keys
Following are the types of shaft key:
1. Parallel Keys: ( Types of Shaft Keys )
These keys can be square or rectangular with regular in thickness
and width all over. They are taper less and can be used at the
place where gear, pulley and other mating part are needed to
slide beside shaft. They are commonly used in automotive
engineering and mechanical engineering due to their ease of
installation and availability.
Parallel keys are generally used for transmitting the unidirectional
torques which have light initial loads and at the place which need
sliding of hub or periodic clearance.
2. Sunk Keys: ( Types of Shaft Keys )
Sunk key is a type of key which can fit into the keyways in both
the member in machinery as well as in the shaft. To the half of
the thickness of the shaft sunk keys are sunk and from the side
of the key measurement are taken. Sunk keys are of several of
types such as Woodruff key, Gib head key, Feather key, Parallel
sunk key, Square sunk key, Rectangular sunk key.
3. Rectangular and Square Sunk Keys:
( Types of Shaft Keys )
These keys are usual proportion of width and thickness of key
and diameter of hole in hub or the diameter of the shaft. They are
installed in shaft for transmitting gear from shaft to shaft and
other element. Machine keys are made up of same material but
are generally tougher and harder than other components as well
as shafts with which they are to be used but sometimes soft keys
are chosen so that it will turn off at the time of excessive force
therefore prevent the damage of expensive equipment.
One of the major difference between square sunk key and the
rectangular sunk key is that in case of a square sunk key the
width and the thickness are equal. Square sunk keys are
generally used for shafts with their diameter between 0.635 cm
to 2.54 cm but there are some larger keys of diameter about 6.5
inch are available for the shafts.
4. Feather Keys: ( Types of Shaft Keys )
These are rectangular keys which is used for connecting the
shaft’s keyway and hub of pulley or gear and can be fastened by
one keyway and are free for sliding from other therefore the hub
are driven by shaft at different positions with it.
Feather keys are drive key which can used for transmitting the
torque from shaft to the driven component. Shaft’s mating slot is
machined with end mill which matches with the design of shaft
key radius. When the key is installed they are contained in
machined pocket and are not able to move axially.
These keys are parallel key and can be rectangular and square.
The shaft’s mating key slot are mechanized with the end mill
cutting tool with same length of wing key and the oval shape
restrict the axial motion and hold the key in shaft.
Feather keys have various benefits over the
tradition keys:
The assembly is simplified and the keys are inserted easily in
the shaft. Radius helps in aligning the key in the slot of the
shaft.
The keys are completely contained and the keys cannot come
out of assembly.
Reforms and disassembly of the feather key is trouble free.
Feather key cannot come out of the shaft and results in
damaging the nearby machines, generally in case of loose key
damage and injury take place.
Feather key do not require any cutting, measuring, fitting or
filling because they can be undone to same length.
Feather key after installing cannot run axially which results in
adjusting the position of component which is mounted along
the shaft.
5. Splines Keys: ( Types of Shaft Keys )
Splines keys are generally formed with shaft inseparably and they
can fit with keyway which is fitted to hub and these shafts are
also called splendid shafts. Splines keys have generally sixteen,
ten, six or four partitions. In comparison with single keyway
shafts, peeled shafts are stronger.
For force transmission in sliding gear transmission and
automobile transmission spoiled shafts are used. With the use of
split shafts, we can have a positive drive as well as axial
movement.
6. Gib Head Keys: ( Types of Shaft Keys )
These keys are notched machine keys which are tapered and are
used for power transmission in keyed shaft for holding the gears
and pulleys tightly on the shaft. The head of the key reduce the
effect of hammering and prevent the damage to the shaft. The
axial position is controlled by the depth in slot in shaft as well as
the component.
More keyway depth or key slot enable to slide the key into the
slot and therefore came in contact with component face.
Therefore we cannot rely on the gib head key and can expect it to
be failed.
7. Woodruff Key: ( Types of Shaft Keys )
These keys are shaft key which are made in segment form of disk
and can be used with the shaft of less than 6.35 cm diameter.
These keys left a flat end protruding after being placed. The
keyway have semi circular pocket which set in the shaft, and the
pockets are set by the help of a cutter for setting the dimensions.
These keys are used for the improvement of concentricity of shaft
for the operations of high speed. The major advantages of using
these keys are to eliminating making of keyway around the place
which has stress. Material used for woodruff keys are generally
stainless steel.
8. Tangent Keys: ( Types of Shaft Keys )
These keys are generally used for heavy duty equipment.
Tangent key are a pair, and the pair of keys are kept at a right
angles with each other and are tangent with the shaft’s surface.
Each of the pair key can resist torsion in only one direction.
Keyway is almost same to parallel key but the only difference is
that it can exits tangent to inner shaft from the outer shaft. For
shaft’s reversible motion one more key is required with the
tangent to opposite direction. The tangent keys can be of any
shape such as rectangular, square or wedge. However the most
commonly used tangent keys are rectangular double taper keys.
9. Circular or Round Keys: ( Types of Shaft
Keys )
These keys have circular section and are partially drilled in the
holes of hub and partially in shaft. The major advantage using
round key is that their key drills are performed again after
assembling the mating part. They are best suited for generally
low power drives.
10. Saddle Keys: ( Types of Shaft Keys )
These keys are used to secure a member with the machine shaft
which can fits with the machine shaft which can fits with the
keyway in member and they are concave so that they can grip
the shaft with friction. As compared with sunk keys, these keys
cannot sunk in shaft and hub, they can sunk in the hub only.
Saddle key generally sit on circumference or a flat of shaft.
Transmission of power is done by the friction in between the key
and the shaft.
Generally Saddle Keys are of Two Types:
A) Flat Saddle Key
These are taper key which is fit in the keyway provided in hub
and they lie flat on shaft. They are usually used for light loads.
B) Hollow Saddle Key
These are taper keys which can fit in the keyway provided in hub.
These key are gripped with friction and they are usually used for
light loads and are used for temporary fastening in case of fixing
and installation of cams, eccentrics etc.
Advantages of Shaft Keys
Their construction cost is less.
Used for high to medium transmission.
They are easily dismantled as well as reusable.
Disadvantages of Shaft Keys
They need stop lock for transmitting axial force.
They can result in imbalance in shaft.
For shaking and alternating directional loads they are not
suitable.
After long time, it is difficult to eliminate the joint.
