-Cutting (Edited from Wikipedia)

SUMMARY

A screw-cutting lathe is a machine (specifically, a lathe) capable of cutting very accurate screw threads. It uses a process of guiding the linear motion of the tool bit in a precisely known rate to the rotating motion of the workpiece.

The name "screw-cutting lathe" carries a qualification on its use—it is a term of historical classification rather than one of current commercial terminology. Early , many centuries ago, were not adapted to screw-cutting. Later, from the Late Middle Ages until the early nineteenth century, some lathes were distinguishable as "screw-cutting lathes" because of the screw-cutting ability specially built into them. Since then, most metalworking lathes have this ability built in, but they are not called "screw-cutting lathes" in modern language.

HISTORY

The screw has been known for millennia. Archimedes devised the water screw, a system for raising water. as mechanical fasteners date to the first century BCE. Although screws were tremendously useful, the difficulty in making them prevented any widespread adoption.

The earliest screws tended to be made of wood, and they were whittled by hand, with or without the help of turning on a lathe with hand-controlled turning tools (, knives, gouges), as accurately as the whittler could manage. It is likely that sometimes the wood blanks that they started from were tree branches that had been shaped by a vine wrapped helically around them while they grew. (In fact, various Romance words for "screw" come from the word root referring to vines.) Walking sticks twisted by vines show how suggestive such sticks are of a screw.

Early machine screws of metal, and early wood screws [screws made of metal for use in wood], were made by hand, with files used to cut the threads. One method for making fairly accurate threads was to score a rod using an inclined knife with a wrap half way around the rod, the knife being precisely angled for the proper pitch.

1 This was one of the methods Maudslay used to make his early leadscrews. This made the screw slow and expensive to make, and its quality highly dependent on the skill of the maker. A process for automating the manufacture of screws and improving the accuracy and consistency of the thread was needed.

The first truly modern screw-cutting lathe was likely constructed by Jesse Ramsden in 1775. His device included a leadscrew, slide rest, and change-gear mechanism. These form the elements of a modern lathe and are in use to this day. Ramsden was able to use his first screw-cutting lathe to make even more accurate lathes. With these, he was able to make an exceptionally accurate dividing engine and in turn, some of the finest astronomical, surveying, and navigational instruments of the 18th century.

Others followed. Examples were a French mechanic surnamed Senot, who in 1795 created a screw-cutting lathe capable of industrial-level production, and David Wilkinson of Vermont, who employed a slide rest in 1798.

However, these inventors were soon overshadowed by Henry Maudslay, who in 1800 created a screw-cutting lathe that is frequently cited as the first. Clearly, his was not the first; however, his did become the best known, spreading to the rest of the world the winning combination of leadscrew, slide-rest, and change gears, in an arrangement practical to use and robust enough for cutting metal.

These late-18th-century screw-cutting lathes represented the breakthrough development of the technology. They permitted the large-scale, industrial production of screws that were interchangeable. of threads (including thread angle, pitches, major diameters, pitch diameters, etc.) began immediately inside companies, and by the end of the 19th century, it had been carried to the international level.

MAUDSLAY

Henry Maudslay (pronunciation and spelling) (22 August 1771 – 14 February 1831) was a British machine tool innovator, , and inventor. He is considered a founding father of machine tool technology. His inventions, such as the first industrially practical screw-cutting lathe in 1800 which standardized sizes for the first time which in turn allowed the application of (a prerequisite for ), were an important foundation for the .

Maudslay began work at the age of 12 as a "powder monkey", one of the boys employed in filling cartridges at the Arsenal. After two years, he was transferred to a carpenter’s shop followed by a ’s forge, where at the age of fifteen he began training as

2 a blacksmith. He seems to have specialized in the lighter, more complex kind of forge work. During his time at the Arsenal, Maudslay also worked at the Royal Foundry.

Maudslay acquired such a good reputation that , a famous lockmaker, called for his services on the recommendation of one of his employees. Bramah was surprised that he was only eighteen, but Maudslay demonstrated his ability and started work at Bramah’s workshop in .

In 1797, after having worked for Bramah for eight years, Maudslay was refused a wage increase to 30s a week so he decided to set up his own business. In 1798 he obtained a small shop and smithy in Wells Street, off Oxford Street but in 1800 he moved to larger premises in Margaret Street, Cavendish Square.

It was in 1800 when he built his screw-cutting lathe.

By 1810 Maudslay was employing eighty workers and running out of room at his workshop, so he moved to larger premises. Maudslay also recruited a promising young Admiralty draughtsman, Joshua Field, who proved to be so talented that Maudslay took him into partnership. The company later became Maudslay, Sons and Field when Maudslay’s sons became partners.

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