Which component aids in the assembly of rotating parts in machinery?

The key, specifically the woodruff key, is an essential component that aids in the assembly of rotating parts in machinery by ensuring a secure connection between the shaft and the component it drives, such as a gear or pulley. The woodruff key is a semicircular piece of metal that is inserted into a slot on the shaft, allowing it to engage with a corresponding slot in the rotating part. This arrangement prevents slippage and ensures that the rotational force is effectively transmitted.

In machinery, accurate alignment and secure attachment are critical for the smooth operation and longevity of rotating components. The woodruff key is designed to fit into the keyway of both the shaft and the attached equipment, preventing relative motion between them and ensuring proper functioning. This method of coupling is widely used in mechanical assemblies, where precision and reliability are paramount, making the woodruff key a fundamental element in rotating machinery.

The other options—square iron, door lock, and drawer lock—do not serve this specific mechanical purpose. Square iron might refer to metal sometimes used in framing or construction, while door locks and drawer locks are designed for securing access and do not contribute to the assembly or function of rotating machinery.