Hexagonal slot

The head of the fastener is usually cylindrical in shape with a hexagonal recess. To work with slots of this type, a hex key (in-key key) or a bit with a corresponding tip is used.

The nominal size of the slot and the key is the distance between opposite parallel faces of the hexagon, which is expressed in millimeters (in this case, for the key measurement method and tolerances, see GOST 8560-78) or fractions of an inch .

The hexagonal slot should be distinguished from other similar types, for example, in the form of a six-pointed star (English TORX ). Hex keys and socket wrenches with an internal hexagon ^[1] (in the form of a hex tube) are also distinguished. The latter are designed to work with nuts, and ordinary hexagon head screws and bolts .

Inbus Key

INBUS (read - inbus ) is a registered trademark of Acument Global Technologies ^[2] , indicating the shape of the Allen key and the corresponding recess in the fastener. It is usually made in the form of a L-shaped curved hexagonal rod, and is often called a hex wrench .

Title History

The name inbus is an abbreviation of it. In nensechskantschraube B auer u nd S chaurte - Bauer & Schaurte hexagon socket head screw. In 1936, Bauer & Schaurte from Neuss in Germany (today owned by Textron ) used a new type of hexagon socket screw, which made it possible to increase the torque by about 10 times compared with a cross-shaped hole. .

Allen's Key

It is believed that hex keys were invented independently in different countries. For example, in the USA, hex keys are called Allen keys. It is believed that in the years 1860-1890 several patents were registered for different types of splines ^[3] , among which also a hex key was used ^[4] , while it was noted that the keys were not produced due to limitations of existing technologies. In 1908, Peter Robertson was the first to patent the method of manufacturing square keys, and already in 1910, William Allen patented the manufacture of hex keys, which were produced by his company Allen Manufacturing Company of Hartford ^[5] . In addition, Sir Howard Gallowell sets forth another version of events ^[6] , according to which the Standard Pressed Steel Company (SPS), founded by him in 1911, independently developed a method for manufacturing keys and began their production, having encountered difficulties in manufacturing Robertson square slot fasteners .

Wrenches and screwdrivers are measured by the distance between parallel faces. Modern metric key labeling contains only the key size in millimeters . Sometimes keys are marked with the letter "M", for example, M4 or M6.

Standard metric dimensions are defined in ISO 2936: 2001, “Assembly tools for screws and nuts — Hexagon socket screw keys” (also known as DIN 911), and, when measured in millimeters, are the following values:

• 0.7; 0.9; 1.0; 1.25; 1.3 and 1.5
• 2 to 6 increments of 0.5 mm
• from 7 to 22 in increments of 1 mm
• 24, 25, 27, 30, 32, 36, 42 and 46 mm.

In addition to metric, inch sizes are also used, which are defined in the ANSI / ASME B18.3-1998 standard “Socket Cap, Shoulder, and Set Screws (Inch Series)”. A good example is that Harley Davidson motorcycles are traditionally made only in an inch gauge system, both in terms of threaded connections and key sizes.

Inch keys may be marked SW with a slot size in fractions of an inch. The standard defines dimensions without limiting the appearance of new ones. The table shows the common sizes, in bold those that are defined by the standard are highlighted.

It must be clarified that the use of metric keys in inch fasteners and vice versa leads to the destruction of a slot or tool, by the way, as well as the use of an incorrect key size (the key must fit tightly into the hole on the fastener). The only exceptions are sizes 5/32 and 5/16 for metric keys 4 mm and 8 mm, respectively - they are practically exactly suitable, therefore they are considered preferable for use in products, for example, requiring self-assembly, due to the fact that you can find an inch key in Russia or some European countries can only be in specialized stores.

There is a version of keys with a hole called anti-vandal. The bottom line is that there is a pin in the center of the fastener hole that prevents the use of conventional keys. Suitable keys have a corresponding hole in the center, are not made in the form of a L-shaped key, and are less often sold. As a rule, they are made in the form of a screwdriver-insert for a tool that works with inserts. TORX keys also have this option.

To work at an angle, the long end of the L-shaped key can be made in the form of a ball, which allows you to tighten the screws at an angle to the axis of the thread. This type of key was invented by Bondhus Corporation in 1964 ^[7] . Usually, the screw is only screwed on to this end, and tightened by the short end, because, firstly, the ball joint is weaker, and, secondly, the long end has a larger lever.

In the American TV series “ Escape, ” the main character Michael Scofield made a hex screwdriver (similar to Allen’s key) from a bolt and, using it, unscrewed the screws that secured the toilet in the cell.

• Wrench
• Torx
• Square (spline connection)

• Burton, Walter E. (February 1946), Hold Everything , vol. 148, New York, NY, USA , < https://books.google.com/books?id=2yADAAAAMBAJ&pg=PA149#v=onepage&f=true >  
• Hallowell, Howard Thomas, Sr (1951), How a Farm Boy Built a Successful Corporation: An Autobiography , Jenkintown, Pennsylvania, USA: Standard Pressed Steel Company, OCLC 521866  

• ISO 2936: 2001 (unspecified) (inaccessible reference) (June 21, 2007). - Assembly tools for screws and nuts - Hexagon socket screw keys. Date of treatment March 6, 2010. Archived March 4, 2016.
• GOST 11737-93 ( unopened ) (inaccessible link) (07/01/1995). - Keys for hexagon socket screws. Technical conditions Date of treatment March 6, 2010. Archived March 4, 2016.