21st May 2020, Periods 2, 3 & 5, Class 12, Engineering Graphics, Machine Parts - Practical

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
3. Gib Head Taper Key
4. Double headed feather key

2. Wood ruff Key

Wood ruff key is a special sunk key. Its looks like a segment of a circular disc. The seat of the key is semi circular in shape. The top of the key way is rectangular. The key way is smaller than the key seat. The advantage of the wood ruff key is that it can be easily adjusted in the recess. It is largely used in machine tools and automobiles.




Exercise

Q 1. Sketch freehand the FV, TV and Side View of a wood ruff key, suitable for a shaft of diameter 40 mm. Give standard dimensions.