What type of nipple would likely be used to connect two threaded pipes?

The type of nipple that is typically used to connect two threaded pipes is known as a shoulder nipple. A shoulder nipple features a shoulder at one or both ends, which allows for a secure connection and provides a stop for the fitting or pipe to tighten against. This design ensures that the connection can handle the stresses of fluid movement and maintains a tight seal, which is crucial for preventing leaks.

These nipples are particularly useful in applications where fittings need to be connected at a specific angle or alignment because the shoulder assists in aligning the components correctly. The shoulder design also adds strength, making it resistant to damage or failure in high-pressure systems.

In contrast, a hex nipple has a hexagonal shape for easy gripping and tightening with a wrench but lacks the shoulder feature that adds stability to the connection. A cross nipple is used to connect four pipes at a central point, making it unsuitable for two-pipe connections. A tapered nipple, while useful in certain contexts, features a taper that generally allows for a tight seal as the thread engages but does not provide the same support as a shoulder nipple when joining two threaded pipes.