When tightening male threads on fasteners, how many threads should protrude beyond the top of the nut?

When tightening male threads on fasteners, the goal is to ensure proper engagement and to avoid potential failure or stripping of the threads. Allowing at least one thread length to protrude beyond the top of the nut provides several benefits. It helps ensure that the load on the fastener is distributed properly and that the joint is secure and stable. This protrusion also enables a visual indicator that the fastener is adequately engaged; if the threads are completely recessed within the nut, it could suggest insufficient tightening or engagement.

In contrast, not allowing any threads to protrude can lead to a weak connection. If there are only half a thread or less protruding, the fastener may not be securely fastened, risking it loosening under load or vibration. This engagement principle is essential in mechanical systems, where maintaining strength and integrity in fastened connections is crucial for operational safety and effectiveness.