22nd May 2020, Period 3, Class 12, Engineering Graphics, Machine Parts - Keys

Dear Students,

Good Morning and a warm welcome to today's class.

It feels really nice to meet up for yet another class this morning.

Recall that in our last class, we had learnt about the RIVETS.

Let us now proceed further and learn about another machine part called as KEYS.


What is a KEY?

A key is a piece of metal which is used to fasten two parts together. More specifically, a key is used to join or tighten two circular moving parts together. For example, moving parts such as pulleys and flywheels are joined to the shaft by means of a key. A key prevents relative motion between the two parts so that these can rotate as one composite part. The key can be unfastened and removed. Therefore it is a temporary fastener.

There is a groove cut out on the shaft as well as the pulley, within which a key is seated. The groove is called as the key way.

Types of Keys

1. Rectangular Sunk Key
2. Wood ruff Key

Feather Keys

3. Gib Head Taper Key
4. Double headed with Gib Head



3. Gib Head Taper Key

A Taper key is uniform in width but tapered in height. The bottom surface of the key is straight and the top surface is tapered. Sometimes, taper keys also have a gib head for easier removal of the key during disassembly. The gib head prevents relative motion between the hub and the shaft.   

   

4. Double headed feather key with Gib Head

A feather key is a kind of sunk parallel key. In parallel key, the thickness of the key remains the same throughout the length of the key. A key that has gib head at both the ends is called as the Double headed feather key with Gib Head. The hub is gripped between its gib heads.




Exercise

Q 1. Sketch freehand the FV, TV and Side View of a double headed gib key, suitable for a shaft of diameter 60 mm. Give standard dimensions.