Friday, December 5, 2014

8 Little Known Facts about the History of the Screw


Many of the workman’s tools we use today were invented during the Roman Age or even before.

Rybczynski explores the histories of several other tools such as the saw, the plane, the chisel, and the level. He discovers that all of these tools were invented during the Roman age if not before. The chisel, for example, dates from the Bronze Age.

2) The threading on a screw forms the shape of a helix, not a spiral.

This is a common mistake. Rybczynski writes, “A spiral is a curve that winds around a fixed point with a continuously increasing radius…A helix…is a three-dimensional curve that twists around a cylinder at a constant inclined angle” (111). Spiral staircases form helixes, not spirals.

3) The screw firsts appears in machinery during the time of the Ancient Greeks, when screws were used in presses of various kinds.

Screws were first used in olive presses and grape presses. In the Middle Ages, this mechanism was adapted for use in the printing press and the paper press. The screw mechanism allows for tremendous force to be exerted on the object being pressed with minimal effort. For example, imagine a press whose large screw has a pitch of one inch and which is turned by means of a handspike three feet long. A pressure of only 40 pounds on the handspike will exert a pressure of more than nine thousand pounds on the olives or grapes.

4) Some of the earliest screws to be used as fasteners were used in military weapons.

For example, screws were widely used in putting firearms together in the early 16thcentury. The threads provided a snugger fit that could survive the vibrations from the firing gun. Screws were also widely used in assembly armor. When screws are inserted into metal their threads must be fairly accurate in order to fit properly into the receiving threads. These screws were created by first hammering out a head and shank and then cutting the thread using a die called a screw plate.

5) Screws were originally used as fasteners for fixing two relatively thin pieces of material together.

Nails are more effective when they are longer. Even a tiny screw when properly installed will remain permanently fixed. To remove a screw without a screwdriver, one actually has to cut away the surrounding material.

6) Although screws were in use as fasteners by the mid-fifteenth century, factory production of screws didn’t start until the mid-1700’s.

As a screw manufacturer, it’s hard to imagine screws being carved by hand. Whole families literally worked day and night to file threads and cut slots in the heads of the screws. In England, blacksmiths delivered large quantities of nails formed with heads to families who then cut a slot in the head and laboriously filed the threading by hand. Not surprisingly, this tedious labor produced poor results-the screws were uneven with shallow threads. The cost of producing screws in this manner was so high that screws were sold individually.

7) The first screw factory was a financial failure.

In 1760 England, Job and William Wyatt patented a design for a machine that could produce screws automatically. It took them 16 years to raise the capital to open a factory. The Wyatt’s machine made a labor of several minutes into one of six or seven seconds while producing a much higher quality product. For some reason, the Wyatt brothers’ business was not successful. Their successors, however, were able to make their business profitable and produced 16,000 screws a day with a team of 30 people.

8) A machine for producing tapered threads was not invented until 1842.

At the time, the lathes that produced screws were incapable of producing the tapered threading visible on a modern screw. Without tapering, the thread could not continue until the tip of the screw. This meant that a hole needed to be drilled before a screw could be installed. In the 1840’s, several American manufacturers received patents for machines that could produce a tapered thread. This technological innovation helped the United States become the most important screw manufacturer in the world.

Overall, a very engaging read. Make sure to check out Rybczynski's book to learn more about the history of hand tools and machinery.

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