Final answer:
A center punch is used to indent metal before drilling a hole, driving pins, or aligning holes. It marks the workpiece to guide precise actions and helps manufacture parts that fit tightly.
Step-by-step explanation:
To indent metal before you drill a hole, to drive pins, or to align holes in two parts that are mates, you would use a center punch. A center punch is a tool with a pointed end that is used to make a small dent in a workpiece. This small dent or dimple serves as a guide for drilling and helps to prevent the drill bit from wandering. When driving pins or aligning holes, the center punch marks provide precise locations for these actions. In manufacturing, it is essential to have tight fitting components; using a center punch helps ensure the precision required for such fits.
In the context of getting a tight fit of a metal peg in a hole in a metal block, the peg would typically be manufactured to a very specific tolerance that is either the same size or slightly larger than the hole it is meant to fit into. This precise sizing facilitates a snug fit, which is often critical in ensuring the structural integrity and functionality of machine parts. Sometimes, a technique known as an interference fit (also known as a press fit) is used, meaning the peg is intentionally made slightly larger than the hole to create a very tight fit without the need for additional fasteners.