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Screw-cutting lathe
A screw-cutting lathe is a machine (specifically, a lathe) capable of cutting very accurate screw threads via single-point screw-cutting, which is the process of guiding the linear motion of the tool bit in a precisely known ratio to the rotating motion of the workpiece. This is accomplished by gearing the leadscrew (which drives the tool bit's movement) to the spindle with a certain gear ratio for each thread pitch. Every degree of spindle rotation is matched by a certain distance of linear tool travel, depending on the desired thread pitch (English or metric, fine or coarse, etc.).
The name "screw-cutting lathe" carries a taxonomic qualification on its use—it is a term of historical classification rather than one of current commercial machine tool terminology. Early lathes, 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 taxonomy.
The screw has been known for thousands of years. Archimedes described the water screw, a system for raising water. Screws as mechanical fasteners date to the first century BC. Although screws were tremendously useful, the difficulty in making them prevented any widespread adoption. The designers of screw-cutting lathes aimed to solve this problem with their machines in such a manner that would enable the production of screws cheaply and efficiently. It would be these qualities of screw production that enabled the utilization of screws in an industrializing world.
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 (chisels, knives, gouges), as accurately as the whittler could manage. It is likely that sometimes the wood blanks that they started from were tree branches (or juvenile trunks) 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 halfway around the rod, the knife being precisely angled for the proper pitch. 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.
Lathes have been around since ancient times. Adapting them to screw-cutting is an obvious choice, but the problem of how to guide the cutting tool through the correct path was an obstacle for many centuries. Not until the late Middle Ages and early modern period did breakthroughs occur in this area; the earliest of which evidence exists today happened in the 15th century and is documented in the Mittelalterliche Hausbuch. It incorporates slide rests and a leadscrew. Roughly contemporarily, Leonardo da Vinci drew sketches showing various screw-cutting lathes and machines, one with two leadscrews. Leonardo also shows change-gears in some of these sketches.
In the succeeding three centuries, many other designs followed, especially among ornamental turners and clockmakers. These included various important concepts and impressive cleverness, but few were significantly accurate and practical to use. For example, Woodbury discusses Jacques Besson and others. They made impressive contributions to turning, but the context in which they tended to work (turning as a fine art for rich people) did not channel their contributions toward industrial uses.
Henry Hindley designed and constructed a screw-cutting lathe circa 1739. It featured a plate guiding the tool and power supplied by a hand-cranked series of gears. By changing the gears, he could cut screws with different pitch. Removing a gear permitted him to make left-handed threads.
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Screw-cutting lathe AI simulator
(@Screw-cutting lathe_simulator)
Screw-cutting lathe
A screw-cutting lathe is a machine (specifically, a lathe) capable of cutting very accurate screw threads via single-point screw-cutting, which is the process of guiding the linear motion of the tool bit in a precisely known ratio to the rotating motion of the workpiece. This is accomplished by gearing the leadscrew (which drives the tool bit's movement) to the spindle with a certain gear ratio for each thread pitch. Every degree of spindle rotation is matched by a certain distance of linear tool travel, depending on the desired thread pitch (English or metric, fine or coarse, etc.).
The name "screw-cutting lathe" carries a taxonomic qualification on its use—it is a term of historical classification rather than one of current commercial machine tool terminology. Early lathes, 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 taxonomy.
The screw has been known for thousands of years. Archimedes described the water screw, a system for raising water. Screws as mechanical fasteners date to the first century BC. Although screws were tremendously useful, the difficulty in making them prevented any widespread adoption. The designers of screw-cutting lathes aimed to solve this problem with their machines in such a manner that would enable the production of screws cheaply and efficiently. It would be these qualities of screw production that enabled the utilization of screws in an industrializing world.
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 (chisels, knives, gouges), as accurately as the whittler could manage. It is likely that sometimes the wood blanks that they started from were tree branches (or juvenile trunks) 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 halfway around the rod, the knife being precisely angled for the proper pitch. 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.
Lathes have been around since ancient times. Adapting them to screw-cutting is an obvious choice, but the problem of how to guide the cutting tool through the correct path was an obstacle for many centuries. Not until the late Middle Ages and early modern period did breakthroughs occur in this area; the earliest of which evidence exists today happened in the 15th century and is documented in the Mittelalterliche Hausbuch. It incorporates slide rests and a leadscrew. Roughly contemporarily, Leonardo da Vinci drew sketches showing various screw-cutting lathes and machines, one with two leadscrews. Leonardo also shows change-gears in some of these sketches.
In the succeeding three centuries, many other designs followed, especially among ornamental turners and clockmakers. These included various important concepts and impressive cleverness, but few were significantly accurate and practical to use. For example, Woodbury discusses Jacques Besson and others. They made impressive contributions to turning, but the context in which they tended to work (turning as a fine art for rich people) did not channel their contributions toward industrial uses.
Henry Hindley designed and constructed a screw-cutting lathe circa 1739. It featured a plate guiding the tool and power supplied by a hand-cranked series of gears. By changing the gears, he could cut screws with different pitch. Removing a gear permitted him to make left-handed threads.