Which type of thread should be chosen for applications requiring high strength over difficult conditions?

For applications that require high strength in challenging conditions, coarse threads are the preferred choice. Coarse threads have a larger pitch and deeper crests, which provide greater surface area for load distribution. This characteristic enhances their tensile strength, making them more resistant to stripping and breaking under stress.

Further, coarse threads are better suited for use in materials with lower tensile strength, as they are less likely to cause localized stress concentrations compared to finer threads. In scenarios where vibration or shock loads are present, coarse threads also tend to hold their grip better and are easier to assemble and disassemble, which is beneficial in adjusting or maintaining equipment under difficult conditions.

In contrast, fine threads, while offering greater precision and the ability to provide a tighter fit, are typically more susceptible to stripping and are not ideal in high-strength applications. Unified threads and Acme threads serve specific functions such as standardization in manufacturing or linear motion applications, rather than being optimized for high strength in adverse conditions.