Trepanning is performed for producing a large hole without drilling.

Introduction:
Trepanning is a machining process used to produce large holes in solid materials, such as metals or plastics. It involves removing a core or plug from the workpiece, leaving behind a large hole with a specific shape and size. This process is commonly used in various industries, including automotive, aerospace, and manufacturing.

Explanation:
Trepanning is performed for the purpose of producing a large hole without drilling. Let's understand why this is the correct answer:

1. Finishing a drilled hole:
Trepanning is not typically used for finishing a drilled hole. Finishing processes such as reaming or honing are commonly employed to achieve the desired surface finish and dimensional accuracy of a drilled hole.

2. Truing a hole for alignment:
Truing a hole for alignment refers to the process of ensuring that a hole is properly aligned with other features or components. This is usually done using alignment tools or fixtures and does not involve the removal of material from the workpiece, which is the primary objective of trepanning.

3. Enlarging a drilled hole:
While trepanning can be used to enlarge a drilled hole, it is not the primary purpose of this machining process. Enlarging a hole can be achieved through other methods such as boring or reaming, which are specifically designed for this purpose.

4. Producing a large hole without drilling:
Producing a large hole without drilling is the main objective of trepanning. This process involves using a trepanning tool, which is a specialized cutting tool with a hollow cylindrical shape. The tool is guided into the workpiece, and the central core or plug is gradually removed, leaving behind a large hole with the desired shape and size. Trepanning is particularly useful when drilling is not feasible or when a larger hole is required than what can be achieved through conventional drilling methods.

In conclusion, trepanning is performed for the purpose of producing a large hole without drilling. This process is an effective solution when a larger hole size is required or when drilling is not suitable for the material or application.