🔍 Key Concepts

• wrist pin (gudgeon pin) function and movement inside the piston • How the wrist pin is axially retained so it cannot slide sideways and hit the cylinder wall • Typical small, removable mechanical retainers used in piston pin bores

💭 Think About

• Think about which option is commonly used to keep a pin from sliding side-to-side in a round bore. • Ask yourself: which choice is a device specifically designed to fit into a groove and hold a pin or shaft in place? • Consider which options are normally used for wear surfaces versus positive locking of a pin.

✅ Before You Answer

• Identify which choice is normally used as a locking retainer for pins in machinery. • Eliminate any items that are primarily used for lubrication or bearing surfaces, not for locking. • Picture a piston pin installed: what is placed in a groove at each end of the pin bore to stop the pin from moving outward?