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How It’s Made? – Screws

How It’s Made? – Screws
By Bill Dickson January 18, 2016 14168 Views

Photo Courtesy of The Benjamin

It’s a tool that has been used since the dawn of time. Whether you’re a carpenter, wood worker, DIYer, machinist or you’re just looking to fix up your house, the screw is one of the most important pieces you need to repair any aspect of a project you’re looking for. The question needs to asked though…where did they come from and how are they made. Let’s take a look in ToolPartsDirect.com’s newest feature, How’s It Made?

What exactly are screws and how are they used?

Screws are threaded fasteners and are apart of the same family as bolts and studs. This also includes wood screws and automotive screws as well. The threads (grooves) can run right handed or left handed. There are also two types of screws, machine or wood screws. The machine screw has a constant diameter and joins nuts together while wood screws are tapered and grips to a wooden surface much better.

Brief History

Photo Courtesy of PBS

While the early concepts of screws have been around since 200 BCE, no one knows who first came up with the idea of the screw. Screws did not become popularized until the Renaissance. Those screws were handmade and no one screw was ever the same. It was a time consuming process and mass production of screws was impossible at that time.

Eventually in 1760, Job and William Wyatt, two brothers from England, filed a patent for the first automatic screw-cutting device. Their machine could cut 10 screws per minute and revolutionized the construction industry at that time.

During the 19th century, Englishman Henry Maudslay helped come up with a new method that is still used by global manufacturers today. Maudslay’s machine was the first power-driver screw-cutting lathe. In the US at that same time, David Wilkinson built a screw-cutting lathe and was awarded the American screw patent. New innovations followed and screws continued to be mass produced into and after the American Civil War. Today, most screws are manufactured by thread rolling.

What they are made of?

The most common materials screws are made of today are composed of low-medium carbon steel wire. Other materials used include brass, stainless steel, nickel alloy or aluminum. Steel can be plated with zinc, nickel, chromium or other plating materials. Other screws have extra finish materials for extra protection and those must be compatible with the raw materials the screw is made from.

How are screws designed and formed?

Photo Courtesy of Made How

While it is possible to create unique or custom screws, almost all manufacturers use the threading process to make all modern screws. The machining process is exact, but takes a lot of time, costs a lot of money and is considered a waste of materials.

When first creating a screw, the manufacturers first start with a process called Cold heading. Wire is fed from a mechanical coil through a pre-straightening machine. The wire flows directly into a machine that automatically cuts the wire at its designated point and also cuts the head of the screw blank into its desired shape.

The heading machine uses either an open or closed die that requires on or two punches to create the screw head. The closed die creates an accurate screw blank. On average, the cold heading machine produces 100-500 screw blanks per minute.

Once the screw is cold headed, the blanks are automatically fed to the thread-cutting dies from a vibrating hopper. The hopper guides the screw blanks down a chute to the dies while making sure the screw are in the correct position to be fed into the machine.

Photo Courtesy of Made How

The blank is then cut using one of three screw-making techniques. In the reciprocating die, two flat dies are used to cut the screw thread. One die remains still, while the other moves in a reciprocating manner. The blank is rolled between the two. When the cylindrical die is used, the screw blank is rolled between the two or three round dies to finish the thread. The final stage of thread rolling is the planetary rotary die process. This process holds the screw in place while several cutting machines roll around the blank to create the finished product.

These methods create higher quality screws and retain better durability. This is because the thread is not cut, but impressed into the blank. No material is lost and weakness in the metal is avoided. The threads are positioned precisely and thread-rolling techniques allow more screws to be repeated…up to 2000, parts per minute.

The finished product.

Quality Control

As more companies began to produce screws, standards were needed to increase interchangeability. In 1928, the National Screw Thread Commission was created for that purpose. A unified screw thread system was adopted in 1948 that focused on the number of threads per inch, the pic as well as thread and diameter sizes. In 1966, the International Standards Organization helped create universal restriction on metric and inch size ranges. These standards were eventually accepted as the global standard.

Nov 20, 2015 10:24:11 PM

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