Definition and Classification of Keys
Definition of Key:
Key is a part of a machine or equipment
where it is used to connect the rotating machine element (Hub/Pulley) to the
shaft and enables the torque transmission. The key will have a provision in
both the shaft and therefore the machine element which needed to be connected.
This is called Keyway.
Types of Keys:
Following are the different types of
keys:
1. Sunk Keys
i.
Rectangular Sunk key
ii. Square Sunk Key
iii. Parallel Sunk Key
iv.
Gib Headed Sunk Key
v.
Feather Sunk Key
2. Saddle Keys
i.
Flat saddle key
ii.
Hallow saddle Key
3. Tangent Keys
4. Round Keys
5. Splines
1. Sunk Keys:
When a key is provided with the half
portion in the shaft and the other half portion in the hub, then the key is
known as the Sunk Key.
There are different varieties in the
sunk key.
The rectangular sunk key's nothing but
having the oblong cross-section. The size of the key will be based on the diameter
(d) of the shaft (Or the diameter of the Bore in the hub).
ii) Square Sunk Key:
The Square sunk key is nothing but having the
Square cross-section.
iii) Parallel Sunk Key:
When a square sunk key or the oblong sunk key
having the uniform cross-section with none taper then it are often called as
“the parallel sunk key”. But in the above mentioned the Square sunk key or the
Rectangular sunk key they will be having the taper along the length of the key.
iv) Gib Head Key:
Simply a rectangular sunk key with a
head to facilitate the easy removal is known as the Gib-headed key. as simple
as that.
v) Feather Sunk Key:
A feather key's a parallel key which
is fastened to at least one part (Hub/shaft) with help of the screws called the
feather key. Sometimes a double gib-head key are often a fether key by locking
it the one part (hub/shaft).
vi) Woodruff Key:
The woodruff key's during a piece from
the cylindrical disc as shown within the Figure, and its main advantage is that
it are often adjustable, tilt within the keyway or keyseat.
2. Saddle Keys:
These sort of keys are rarely used
because these cannot transmit the high torque. Saddle won’t have the supply
within the shaft; instead, it holds the shaft by friction. Saddle key has two
variants.
i) Flat saddle key:
A flat saddle key is taper key and
having a provision in the hub only and will be floated on the shaft and hold
the shaft by means of the friction. So it can be used for light loads. It used
for temporary fastening only.
ii) Hallow saddle Key:
A Hallow saddle key is also a taper
key here also it will have the provision in the hub only, but the contact
portion of the key with the shat will be shaped into a curvature to get the
full grip on the shaft for better friction.
3. Tangent Keys:
Tangent keys are used in heavy-duty
equipment. Tangent keys are actually a pair. These pair of keys are placed right
angles to each other and tangent to the surface of the shaft as shown in the
figure. Each key will withstand the torsion in one direction only.
4. Round Keys:
Round keys are circular in section and
fit into the holes. The round keys will be placed half portion hole in the
shaft and the other half portion hole in the hub as shown in the fig. These
sort of shaft keys are usually prepared for the low power drives.
5. Splines:
All the above-mentioned keys are
individual parts. What happens when the keys are integral parts of the shaft or
hub? That what we called as the Splined shafts. These are utilized in the
special applications like where we've to transmit the torque larger in portion
than the shaft size.
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