Couplings are used to connect two shafts for torque transmission. There are two main types of couplings: rigid couplings and flexible couplings. A rigid sleeve coupling consists of a cylindrical cast iron sleeve keyed to the shafts to connect them. It transmits power from one shaft to the other through a key and sleeve.

2.  Couplings are used to connect two shafts for
torque transmission in varied applications.
 Coupling may be rigid or they may provide
flexibility and compensate for misalignment.
 They may also reduce shock loading and
vibration.

3. There are two main types of couplings:
 Rigid couplings
 Flexible couplings
Rigid couplings are used for shafts having no
misalignment while the flexible couplings can
absorb some amount of misalignment in the
shafts to be connected.

4.  One of the simple type of rigid coupling is a
sleeve coupling which consists of a
cylindrical sleeve keyed to the shafts to be
connected.

5.  It is made of cast iron.
 It consists of a hollow cylinder whose inner
diameter is the same as that of the shaft
(sleeve).
 It is fitted over the ends of the two shafts by
means of a gib head key.
 The power is transmitted from one shaft to the
other shaft by means of a key and a sleeve.

6.  The muff or sleeve is made into two
halves and are bolted together.
 The halves of the muff are made of cast
iron.
 The shaft ends are made to a butt each
other.
 A single key is fitted directly in the
keyways of both the shafts.
 One-half of the muff is fixed from below
and the other half is placed from above.

8.  Both the halves are held together by means of
mild steel studs or bolts and nuts.
 The number of bolts may be two, four or six.
 The advantage of this coupling is that the position
of the shafts need not be changed for assembling
or disassembling of the couplings

10. The usual proportions of a cast iron sleeve
coupling are as follows :
Outer diameter of the sleeve, D = 2d + 13 mm
and length of the sleeve, L = 3.5 d
where d is the diameter of the shaft.