Page 171 - CITS - ED - Mechanical

ENGINEERING DRAWING - CITS

Special keys and keys not as per BIS

There are some keys in use though not as per BIS viz
– Dove tail key
– Peg key
– Single head key with screw
– Double head key.

Dove tail key: The rectangular part of the key is fitted into the shaft and dove tail part into the hub. They are driven
into their position by using soft hammers. (Fig 1)
Peg key: Hub which takes the peg key has a suitable hole in the slot. The key is first mounted on to the hub
hole. The shaft is then aligned to the hub. Key is comparatively longer than those used with taper keys. (Fig 2)

Fig 1 Fig 2

Single headed key: After driving into the key way, it is fastened to the hub with a counter sunk screw. (Fig 3a)
Key seat on the shaft to take double headed key is from one end of the shaft. The key is first fitted to the hub and
then the key seat of the shaft is aligned and fixed. (Fig 3b) The key, in all these cases cannot get loosened from
its position of the hub. It allows the hub to slide if required along the axis to some extent.

Cone keys: These are segments of a truncated cone with cylindrical hole, on the axis, when they are mounted on
a shaft, they can take up tapered hollow hub of different dia meters or shafts of varying diameter. (Fig 4)

Fig 3 Fig 4

Tangential keys: two sets of pair of taper keys are used tangential to the shaft. They are used on shaft for dia 60
mm above upto 500 mm (IS:2291)

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CITS :Engineering Drawing (Mechanical) - Exercise 8