What is drilled in the end of a staybolt to warn of corrosion?

The correct answer is that a hole is drilled in the end of a staybolt to warn of corrosion. This small hole serves as an indicator; when corrosion occurs, it compromises the integrity of the staybolt, and the hole allows for the detection of this degradation. If corrosion progresses and metal begins to erode away, the hole can become enlarged or even visible, alerting engineers to potential structural weaknesses before they result in a catastrophic failure.

This practice is essential to maintaining boiler safety and efficiency, as staybolts play a crucial role in holding the boiler structure together under pressure. By proactively monitoring for corrosion through this method, engineers can perform necessary maintenance or replacements, thereby extending the lifespan of the boiler and ensuring safe operation.

In contrast, a notch is typically used to create stress concentration points, which can lead to failure, and a groove could serve various purposes in mechanical assembly but does not specifically indicate corrosion. Threads are important for fastening but do not relate to corrosion detection.