Threads and Applications

What is thread?

In mechanical engineering, a thread refers to a helical ridge or groove on the surface of a cylindrical object, such as a screw, bolt, or stud. Threads are designed to interact with a complementary thread on another object, like a nut or a threaded hole, creating a fastening mechanism. This interlocking action allows for the controlled application of force to hold objects together.

Here are some key terms related to threads in the mechanical context:

Thread Terminology

Thread Pitch:

The thread pitch is the distance between corresponding points on adjacent threads, measured parallel to the axis. It is commonly expressed in millimeters (mm) or threads per inch (TPI).

Thread Angle:

The thread angle is the angle formed by the helix of the thread with a plane perpendicular to the axis. The most common thread angles are 60 degrees for metric threads and 60 or 55 degrees for unified threads.

Major Diameter:

The major diameter is the largest diameter of a thread, measured from crest to crest (outer diameter).

Minor Diameter:

The minor diameter is the smallest diameter of a thread, measured from root to root (inner diameter).

Crest:

The crest is the top surface of a thread.

Root:

The root is the bottom surface between two adjacent threads.

Threads can be classified into various types based on their shape and intended application. Some common types include:

Type of Thread

• Unified Thread Standard (UN/UNR): Used in the United States and many other countries for bolts, nuts, and threaded holes.
• Metric Threads (ISO Metric): Widely used in Europe and other parts of the world, based on the metric system. For standard assemblies that need to be bolted
• Acme Threads: Trapezoidal-shaped threads commonly used for power screws.for controlled moment on machine tools.
• Square Threads: Square-shaped threads used in certain applications requiring high efficiency and strength. As the pitch angle is small, it has low friction and high frequency transmission.

The design of threads in mechanical engineering involves considerations such as strength, ease of manufacturing, and compatibility between mating threads to ensure reliable and efficient fastening. Additionally, threads can be internal (tapped holes) or external (screws, bolts), and they play a crucial role in various applications across industries.

Hope you found all information about threads