overthreading

Overthreading is a term used to describe the act of intentionally or unintentionally creating a screw thread that is larger in diameter than the specified nominal size for a particular fastener or hole. This can occur during the manufacturing process of screws, bolts, or nuts, or when a fastener is inserted into a pre-tapped hole.

In manufacturing, overthreading can result from worn tooling, improper calibration of machinery, or incorrect material feed rates. When a screw is manufactured with an oversized thread, it may not properly engage with the intended mating thread, leading to a loose or weak connection. Similarly, if a tap used to create threads in a hole is worn or improperly used, it can produce an over-tapped hole.

When a fastener is inserted into a hole, overthreading can happen if excessive force is applied, especially if the thread pitch is slightly mismatched or if debris is present. This can strip the existing threads in the hole or deform the threads on the fastener, effectively making them oversized. The result is often a connection that cannot be fully tightened or that feels loose even when torqued.

The consequences of overthreading can range from minor inconveniences, such as a fastener not seating properly, to significant structural failures, depending on the application. In critical engineering applications, such as in aerospace or automotive industries, overthreading is meticulously avoided through strict quality control measures and precise manufacturing techniques. Detecting overthreading typically involves visual inspection and, more reliably, the use of go/no-go gauges to verify thread dimensions.