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The Different Types of Thread Terminology

Fasteners are the nuts, bolts, screws, and other small components that maintain the integrity of machinery and components. Numerous fasteners function through the use of threads (left-hand thread and right-hand thread), which allow nuts and bolts to effectively attach together.


On cylindrical fasteners, threads are continuous helical ridges. For parts such as screws, the ridges are located on the exterior, whereas nuts have ridges on the interior of their cylindrical bodies.

Below, we define a number of common terms used to characterise various aspects of threads.

  • Internal threads: Threads that run along the inside of a fastener.

  • External threads: Threads that wind around the exterior of a fastener’s shaft.

  • Pitch: The distance between a point on one thread to a point on another thread.

  • Axis: Longitudinal lines used to measure the length of the fastener.

  • Minor diameter: The smallest internal or external thread diameter.

  • Major diameter: The largest internal or external thread diameter.

Avlock International is a leading manufacturer and distributor of specialised fastening systems to both the domestic market and other global destinations. For an obligation-free quote or demonstration, contact Avlock today.

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