Ww-thread

What is a WW thread?

The WW thread (Whitworth thread) is a British thread standard developed by engineer Joseph Whitworth in 1841. It was the first standardized threading system widely used in machine shops and machining. The Whitworth thread is characterized by its 55-degree thread angle, which distinguishes it from the later metric ISO thread that features a 60-degree angle.

Use of WW thread in the machine shop industry

WW thread was the standard for a long time, particularly in the UK and internationally, before shifting to the metric system. Even though its usage has decreased, it can still be found in older machines, equipment, and spare parts, making knowledge of it important for machinists and machine shops. This type of threading is also often used in the restoration of steam engines, steam boilers, and other historic equipment.

Features and dimensions of the WW thread

The WW thread is based on imperial measurements, and its thread pitch is specified as the number of threads per inch (TPI, Threads Per Inch). The most common sizes range from 1/16” to 2 ½”. The thread profile is symmetrical, with rounded crests and roots, which helps to reduce stress concentrations and improve durability.

WW thread vs. other thread types

While WW thread is still used for certain applications, most machine shops today use metric ISO threads or other standards such as UNC and UNF threads. However, Whitworth threads can still be found in older machines, so identifying and working with them is important, especially for machinists dealing with traditional systems.

Summary

The WW thread, or Whitworth thread, is a historical British threading system that is still used in older machines and specialized applications. It is based on imperial measurements and differs from metric threads especially in its thread angle and sizing. While it is less commonly used in modern machining, understanding it remains valuable in the machine shop industry.