A brief history of threading

Introduction:

It has been 22 centuries since the idea of Archimedes: he was ingenious enough to design a helical profile capable to transform radial forces into axial ones in order to move water upward. Who could have thought that an invention born to solve a small practical problem would have had such an important role in the modern industry?
Today, "screws hold the world together": the term fasteners comes indeed from the verb "to fasten", which means "to fix, to attach, to connect". And we can say that there are virtually no complex industrial products that do not use fastening systems for their assembly.
Let's retrace together the history of their evolution through the centuries.

Origins:

Attempts and applications of "pivots with helical grooves" can be found in (supposedly) Greek and Egyptian writings dating back to 2500 years ago. However, the true forerunner of modern fasteners is known to be the famous “Archimedes’ screw”, which was invented around 200 BC.

Since then, and for many centuries, the helical groove has slowly evolved, gradually transforming into its current form—a thread.
Its field of application expanded when it was understood that – in addition to moving objects axially – it was possible to join two or more components in a stable and resistant way.
However, its use remained marginal because of the difficulties of screw manufacturing, still very much linked to the skill of the craftsman.
Screw-making was not easy, and it was even more difficult to ensure fasteners worked as required. It was almost impossible to guarantee they were identical.
Everything that was assembled using screws was one of a kind. To be repaired or replaced, components had to be adapted through difficult and expensive operations. The first solutions to this problem began to be seen only after many years, many attempts, many ideas, and many tests.

The first lathe:

Around 1750, Antoine Thiout first built a hand-fed lathe with a nut screw capable of producing threaded parts in a repeatable way.
20 years later, Jesse Ramsden further improved this machine, allowing the manufacture of screws precise enough to be used for the construction of the first control instruments (gauges), which could replicate measurements with acceptable tolerances.

In 1760, given the growing demand for threaded parts, William Wyatt made the first step toward their industrial manufacturing by patenting a machine to batch-produce them.
The first requests of the industry gave a great boost to their use but created also confusion because the shapes, sizes, and profiles of the threads were left to the inventiveness of the designer.

The first standards:

In 1841, Joseph Whitworth gathered information about the most commonly used threaded products. In 1860, he first set what would have been the thread standard for many years to come: a triangular profile with a 55-degree angle.

In 1864, William Sellers developed and proposed a standard thread with a 60-degree triangular profile with various pitch lengths. This became over time the American UNC and UNF standard.

In 1898, Swiss, French, and German scholars began proposing 60-degrees triangular profile metric screws. However, the market shifted toward metric profiles deriving from the Sellers’ model, which was standardized by then.

In 1947, the International Standard Organization (ISO) standardized the metric screws (M) and the BSP threads (R, G) for pipes. Instead, the American screws found a first standardization in the ASME and SAE standard tables and a second one in the Unified Threads Standard (UTS) of 1949.

Since 1950, the market has been demanding multiple thread forms depending on their application: SDS (self-drilling), for drywall, for chipboard, Taptite, Try-lobe, and so on. In turn, installation tools and equipment made their appearance together with special head recesses. From the simple screwdriver slot to more complex shapes, such as Phillips (Type 1), Pozi-Drive (Type 1A), Hexalobate (Torx), and 12Pt, as well as hexagonal recesses, both internal and external.

Today, the most common standards refer to shared regulations with indications of shape, size, precision levels, and materials. They are recognized and accepted by all, both users and manufacturers.

There still exist – and are locally used – national standards (AFNOR for France, UNI for Italy, DIN for Germany, and so on). Among these, the German DIN standard seems to be predominant, but nowadays more and more players tend to adopt ISO standards (to which DINs refer anyway).

The market globalization and the growing demand of the automotive industry have pushed to use new materials for better results: fasteners have evolved at the same pace.

Weight:

Fasteners allow the industry to produce complex parts in ever-increasing quantities. Thanks to screws and bolts, complex parts can be assembled quickly and easily, while offering the same features of a monobloc item. Since they account for a significant part of the total weight of many subassemblies (for example of an automotive engine), manufacturers are always looking for lighter solutions and innovative materials.

Sometimes, less is more.
This may seem like a paradox, but in reality, it is the challenge of the future. The industry is called upon to produce

fewer shapes and sizes in higher numbers, using fewer and lighter raw materials with better technical characteristics and at a lower cost.

Engineers and researchers are constantly engaged in studying new profiles able to guarantee better fastening properties; new head shapes or recesses able to apply higher and higher tightening torques; new, lighter, more resistant yet less expensive materials.

These are the future challenges for an industry – the fasteners one – and an invention – the thread – which have thousands of years of history behind them but still have much to tell.


Literature

• Bhandari, V B (2007), Design of Machine Elements,
• Tata McGraw-Hill, ISBN 978-0-07-061141-2.
• Degarmo, E. Paul; Black, J T.; Kohser, Ronald A. (2003), Materials and Processes in Manufacturing (9th ed.), Wiley, ISBN 0-471-65653-4. 
• Oberg, Erik; Jones, Franklin D.; Horton, Holbrook L.; Ryffel, Henry H. (1996), Green, Robert E.; McCauley, Christopher J. (eds.), Machinery's Handbook (25th ed.), New York, NY, USA: Industrial Press, ISBN 978-0-8311-2575-2, OCLC 473691581.
• Roe, Joseph Wickham (1916), English and American Tool Builders, New Haven, Connecticut: Yale University Press, LCCN 16011753. Reprinted by McGraw-Hill, New York and London, 1926 (LCCN 27-24075); and by Lindsay Publications, Inc., Bradley, Illinois, (ISBN 978-0-917914-73-7).
• Wilson, Bruce A. (2004), Design Dimensioning and Tolerancing (4th ed.), Goodheart-Wilcox, ISBN 1-59070-328-6.
• International Thread Standards
• ModelFixings – Thread Data 
• NASA RP-1228 Fastener Design Manual
Video:
Screws - The Early Years
Brief history of the screws
Giovanni Stagni
Fasteners Area Consultant
Editor's note: for comments and feedback on this article, please write to [email protected].