Sleeve or Muff Couplings

This is the simplest of all couplings. It consists of a sleeve called muff, generally made of cast iron, which is fitted over the ends of the shafts to be connected. After properly aligning the keyways in the shafts and sleeve, a sunk key is driven-in; thus making the coupling. Instead of a single key running the entire length of the sleeve, it is desirable to use two keys, which may be inserted from the outer ends of the sleeve; thus overcoming the possible misalignment between the keyways. The following are the types of muff couplings along with their animation videos.

1.  BUTT MUFF COUPLING: In this, the ends of the two shafts to be coupled butt against each other, with the sleeve keyed to them, as discussed above.

2. HALF-LAP MUFF COUPLING: In this, the ends of the shafts overlap each other for a short length. The taper provided in the overlap prevents the axial movement of the shafts. Here too, after placing the muff over the overlapping ends of the shafts, a saddle key(s) is(are) used to make the coupling.



3. SPLIT MUFF COUPLING: In this, the muff is split into two halves and are recessed. A number of bolts and nuts are used to connect the muff halves and the recesses provided accommodate the bolt heads and nuts. For making the coupling, a sunk key is first placed in position and then the muff halves are joined by bolts and nuts. This type of coupling is used for heavy duty work, since both the key and friction grip transmit the power (torque).


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