| 28) Conversational topic “Dimensions” should include:
• Key dimensions of circles and pipes
The outside edge of a tyre or pipe forms a circle. The outer circle is the outside of the tyre or pipe, and the inner circle - the circle with the smaller diameter. And, clearly, the inner circle is right in the middle of the outer circle - it's exactly in the centre. So because it's central, that means the inside and outside of the tyre form concentric circles. And as the tyre is circular, simple geometry tells us that measurements of the radius, taken from the centre of the circle to different points on its edge are equal. In other words, the tyre has a constant radius. We can say inner diameter and outside diameter about circles and pipes.
• Dimensional accuracy (Precision and tolerance)
When one component goes through another, such as a shaft or a bolt going through a hole, the two must fit together. There are two main types of fit:
• A clearance fit allows a component to slide or turn freely, by leaving clearance (a gap) between itself and the sides of the hole. This distance must be quite precise.
• An interference fit is a very tight fit which does not allow a component to move freely inside a hole. This type of fit can be achieved by forcing the component into the hole.
• Precision and tolerance
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