Screws and Screwdrivers

What is a Screw? What is a Screwdriver?
A screw is any shaft with a corkscrew-shaped groove formed on its surface. are used to fasten two objects together. A screwdriver is a for driving (turning) ; have a tip that fits into the head of a screw.
Early Screws
Around the first century, screw shaped tools became common, however, historians do not know who invented the first. Early screws were made from wood and were used in wine presses, olive oil presses, and for pressing clothes. Metal screws and nuts used to fasten two objects together first appeared in the fifteenth century.
Mass Production of Screws
In 1770, English instrument maker, Jesse Ramsden (1735-1800) invented the first satisfactory screw-cutting lathe. Ramsden inspired other inventors. In 1797, Englishmen, Henry Maudslay (1771-1831) invented a large screw-cutting lathe that made it possible to mass-produce accurately sized screws. In 1798, American David Wilkinson also invented machinery for the mass production of threaded metal screws.
Robertson Screw
In 1908, square-drive screws were invented by Canadian P. L. Robertson. Twenty-eight years before Henry Phillips patented his Phillips head screws, which are also square-drive screws.The Robertson screw is considered the “first recess-drive type fastener practical for production usage.” The design became a North American standard, as published in the sixth edition of Industrial Fasteners Institute Metric and Inch Standards. A square-drive head on a screw can be better than a slot head because the screwdriver will not slip out of the screw’s head during installation. The Model T car made by the Ford Motor Company (one of Robertson’s first customers) used over seven hundred Robertson screws.
Phillips Head Screw
In the early 1930s, the Phillips head screw was invented by Henry Phillips. Automobile manufacturers now used car assembly lines. They needed screws that could take greater torque and could provide tighter fastenings. The Phillips head screw was compatible with the automated screwdrivers used in assembly line.

Ironically, there is a Philips Screw Company that never made Phillips screws or drivers. Henry Phillips died in 1958 at the age of sixty-eight.
Allen Key
A hexagonal or hex screw head has a hexagonal hole turned by a Allen key. An Allen key is a hexagonal shaped wrench. The Allen key may have been invented by American, Gilbert F. Heublein, however, this is still being researched and should not be considered a fact. Heublein was an importer and distributor of foods and beverage. who in 1892 introduced “The Club Cocktails”, the world’s first bottled cocktails.
In 1744, the flat-bladed bit for the carpenter’s brace was invented, the precursor to the first simple screwdriver. Handheld screwdrivers first appeared after 1800.

Types of Screws

  • Cap screw has a convex head, usually hexagonal, designed to be driven by a spanner or wrench.
  • Wood screw has a tapered shaft allowing it to penetrate undrilled wood.
  • Machine screw has a cylindrical shaft and fits into a nut or a tapped hole, a small bolt.
  • Self-tapping screw has a cylindrical shaft and a sharp thread that cuts its own hole, often used in sheet metal or plastic.
  • Drywall screw is a specialized self-tapping screw with a cylindrical shaft that has proved to have uses far beyond its original application.
  • Set screw has no head, and is designed to be inserted flush with or below the surface of the workpiece.
  • Double-ended screw is a wood-screw with two pointed ends and no head, used for making hidden joints between two pieces of wood.

Shapes of Screw Head

  • Pan head: disc with chamfered outer edge.
  • Cheese head: disc with cylindrical outer edge.
  • Countersunk: conical, with flat outer face and tapering inner face allowing it to sink into the material, very common for wood screws.
  • Button or dome head: flat inner face and hemispherical outer face.
  • Mirror screw head: countersunk head with a tapped hole to receive a separate screw-in chrome-plated cover, used for attaching mirrors.

Types of Screw Drive
A variety of tools exist to drive screws into the material to be fixed. The hand-tool used to drive slot-headed and cross-headed screws is called a screwdriver. A power tool that does the same job is a power screwdriver. The hand-tool for driving cap screws and other types is called a spanner (UK usage) or wrench (US usage).

  • Slot head is driven by a flat-bladed screwdriver.
  • Cross-head, or Phillips screw has an X-shaped slot and is driven by a cross-head screwdriver, designed originally in the 1930s for use with mechanical screwing machines, intentionally made so the driver will ride out, or cam out, under strain to prevent over-tightening.
  • Pozidriv is patented, similar to cross-head but with better resistance to slipping, or cam-out.
  • Hexagonal or hex screw head has a hexagonal hole and is driven by a hexagonal wrench, sometimes called an Allen key, or a power tool with a hexagonal bit.
  • Robertson drive head has a square hole and is driven by a special power-tool bit or screwdriver (this is a low-cost version of the hex head for domestic use).
  • Torx head has a splined socket and receives a driver with a splined shaft.
  • Tamper-proof torx is similar to torx but the drive socket has a projection to prevent a standard torx driver being inserted.
  • Tri-Wing screws are used by Nintendo on its Gameboys. This discourages even minor home repairs to the units.

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