Cross screwdriver - the hard history of her invention
A screwdriver is a hand-held tool for screwing and unscrewing threaded fasteners, most often screws and screws, on the head of which there is a slot (groove). Usually it is a metal rod with a tip and a handle (plastic or wooden).
Phillips screwdriver - an indispensable attribute of any set of tools for your father or any workshop. But the story of its invention in the 1930s was not accepted by the community immediately.
The first appearance of classic screws under the screwdriver with a “flat” tip dates back to about the 16th century; they existed almost unchanged until the beginning of the 20th century. By this time, the slotted screws were already causing a lot of complaints, but were out of competition due to their low cost. The drawbacks of the “classic” screws were especially pronounced during mass assembly, in particular, in the automotive industry. First, the sting was not centered, because of this, mechanical screwdrivers often slipped, leaving scratches on the lacquered body parts. Secondly, when tightening the screws and screws often “overtighten”, turning the head or damaging the fasteners. It was these limitations that the American inventor John Thompson was going to overcome, in 1933, having patented a screwdriver with a cross-shaped sting and a screw with the corresponding head. However, an attempt to sell the invention to hardware manufacturers was not crowned with success. In 1934, Thompson met with the engineer Henry Phillips and outlined to him the essence of his invention. Phillips liked the idea, he bought the rights to the Thompson patent and organized the company Phillips Screw Company (it still exists). In 1936, he improved the technology and developed a method for mass production of screws. The cross screws automatically centered the screwdriver and also did not allow “overtightening” - the sting of the tool simply slipped.
However, Phillips was waiting for rejections everywhere. Finally, he managed to interest Eugene Clark, president of the American Screw Company, the largest manufacturer of hardware in the United States. Although the company's engineers objected, Clark so captured the idea that he threatened to “dismiss everyone who says that this is impossible to accomplish.” The threat had an effect, and the company, having invested half a million dollars in organizing the production, began producing screws under the “cross”. In 1937, GM used these screws for the first time in the production of Cadillac models. The results were so brilliant that by 1940 all American automakers switched to the use of crosshead screws, and manufacturers of hardware dozens lined up to purchase a license. During World War II, manufacturers of military equipment, such as tanks and aircraft, also switched to using these screws.
Since then, many different screws have been invented - both for polyhedrons and for sprockets of various shapes. But despite this, the cross screws and screws (in English sources, they are called by the name of the inventor - Phillips) still remain the standard, and the cross screwdriver is the basis of any set of tools.
The simplest screwdriver is usually a rod with a tip, which is inserted into the slot when working, the other end of the rod is equipped with a wooden, plastic or rubber handle. The material of the handle and its shape is chosen for reasons of increasing the adhesion with the hand.
The diameter of the handle is usually in the range from 10 to 40 mm. Since the relationship between the diameter of the handle and the torque delivered to the part is straight, the diameter is usually larger as the size of the parts, the slotted screwdriver, is larger. Therefore, screwdrivers designed for small parts are supplied with thin handles in order to avoid disruption of the slot or thread or break of the part. Some screwdrivers have a hole in the handle that allows you to increase the torque when using a lever that is threaded into this hole, or is used to fasten a safety cord.
The tip of the screwdriver wears out due to the action of significant mechanical stresses during operation. To increase the service life of the tip it is made of special wear-resistant and durable alloys, for example, chromium-vanadium-molybdenum steels.
Types of tips
Depending on the type of slot on the head of the part, screwdrivers with different types of tips are used.
Standard - Received the ubiquitous.
- The straight slot (slotted) is the simplest and historically first type of slot.
- Phillips - self-pushing cruciform. Currently outdated, but continues to be widely used in instrument making, as it is a de facto standard and takes up little space in the head.
- Pozidriv is an upgraded version of the Phillips slot, non-self-pushing. Because of the large depth of the slot is used only where the screws are forced to have large heads: in the furniture industry and construction. However, it is in these industries need a large torque, fundamentally impossible for Phillips.
- Hex slot - allows you to get a large torque.
- Torx (star-shaped six-beam) - allows you to get a large torque, used in the manufacture of household appliances, mechanical engineering.
Special - If special requirements are imposed on the screw, such as beauty, anti-twist protection or a huge tightening force in the compact head, special slots are used.
- Tri-Wing (three-bladed) - used in the aerospace industry and in the manufacture of electronic devices.
- Torq-Set (asymmetrical cross) - used only in the aerospace industry.
- One-way - not provided for unscrewing.
- Two-pin (Spanner) - used in elevators and other places where beauty and vandal protection are required at the same time.
- Slots with a slot-like spanner, used in electrical appliances, power supplies, where amateur intervention is undesirable.
- Torx with pin (Torx Tamper Resistant) - a star-shaped six-ray with a hole in the middle, which includes a pin in the middle of the six-ray groove of the screw.