What is always true about interference fit?

• A. It allows for sliding movement between parts
• B. There is an interference between the axle and the opening
• C. It depends on the alignment of the parts
• D. It only applies to plastic parts

Answer: (B)

In the context of interference fit, it is always true that there is an interference between the axle and the opening. An interference fit, by definition, is a type of fit where the size of the parts is such that they must be forcibly assembled together, causing one part to interfere with the other. This is achieved by designing the external dimension of one part to be larger than the internal dimension of the other part, resulting in a tight, frictional connection that does not allow them to move relative to each other once assembled.

This type of fit is essential for applications requiring high strength and stability, such as in mechanical assemblies where parts must maintain their position under load without the risk of slippage. Understanding the nature of this interference is crucial in engineering applications to ensure proper assembly and functionality of mechanical systems.

Other options do not accurately describe the nature of interference fit: it does not allow for sliding movement, it is not solely dependent on the alignment of parts, and it is not limited to plastic parts – it can apply to a variety of materials, including metals.