Rybczynski describes a flurry of patents for alternative drive types in the s to the s in the US,  which are confirmed to include internal-wrenching square and triangle types that is, square and triangular sockets U. As patents expired and awareness of their advantages spread, Robertson fasteners have become popular in woodworking and in general construction.
Published advertisements for the "Allen safety set screw" by the Allen Manufacturing Company of Hartford, Connecticut, exist from At the least, the design or methods of manufacturing it was patented in various countries by various patentees, and its name varies.
Linear broaching to cut corners into a drilled hole similar to the action of a mortising machine for woodworking has also been used less commonly over the decades. The name derives from overlaying three equal squares to form such a pattern with 12 right-angled protrusions a pointed star. The synonym zeta key or wrench refers to the sixth letter of the Greek alphabet.
Allen patented a method of cold-forming screw heads around a hexagonal die U. The design is similar to that of the double-square —in both cases, the idea being that it resembles a square Robertson but can be engaged at more frequent angles by the driver bit. In —, William G. The book does not mention which method—cold forming gratis blackjack oefenen linear broaching—was used by SPS in these earliest years.
Robertsonof MiltonOntarioCanadafirst commercialized the square socket inhaving perfected and patented a manufacturing method cold-forming, using the right material and the right die design. The headless set screws would be less likely to catch the clothing of workers and pull them into injurious contact with the running shaft. Many of us will have more than one hex socket key in our toolboxes, and indeed it is a good idea to keep hold of the Allen keys which come with our flat pack furniture; screws can benefit from being tightened once in a while to maintain the stability of furniture, particularly chairs and tables, which are subject to the forces of weight and movement together.
Robertson had licensed the screw design to a maker in England, but the party that he was dealing with intentionally drove the licensee company into bankruptcy and purchased the rights at a reduced price from the trustee, thus circumventing the original agreement.
This account from Hallowell does not mention the Allen patent ofnor the Allen safety set screw product line. There is another name in Italian brugolastemming from the name Officine Egidio Brugola, a company who first commercialized Allen's products in Italy. Its use probably increased enormously during World War II. This makes for a much more attractive display as well as being more practical; narrow gaps between pieces of furniture are displeasing to the eye and attract dust and small objects.
The term hex-head is sometimes used to refer to this type of drive, but this use is not consistent with its more conventional use referring to external-wrenching hexagons.
Hallowell said that acceptance of the internal-wrenching hexagon drive was slow at first painfully slow for SPS's salesbut that it eventually caught on quite strongly. This is just one example of how flat pack furniture can work with the individuality of a space to maximise its beauty and usefulness.
This cost problem drove SPS to purchase its first screw machine and make its screws in-house, which soon led to SPS's foray into fastener sales for which it later became well known within the metalworking industries. Originally to make the manufacture of the screws practical using cold forming of the heads, : A hex key should not be used where a key of square cross-section is the correct fit. When Henry Ford tried out the Robertson screws, he found that they saved considerable time in Model T production, but when Robertson refused to license the screw design, Ford realized that the supply of screws would not be guaranteed and chose to limit their use in production to Ford's Canadian division.
Then we decided to incorporate a hexagon socket into the screw […].
Hallowell does describe, however, the same inspiration also mentioned in connection with Allen for a wave of adoption of the hex socket head, beginning with set screws and followed by cap screws.
The restriction of licensing of Robertson's internal-wrenching square may have sped the development of the internal-wrenching hexagonalthough documentation of this is limited.
The design is similar to a square drive Robertsonbut can be engaged at more frequent angles by the driver bit. The beauty of the hex socket screw is its simplicity. Robertson screwdrivers are easy to use one-handed, because the tapered socket tends to retain the screw, even if it is shaken.
SPS at the time was a prominent maker of shaft hangers and collarsthe latter of which were set in place with set screws.
Using a hex wrench on a socket that is too large may result in damage to the fastener or the tool. There are some exceptions to that. Patent, but he explains that these were patented but not manufactured due to the difficulties and expense of doing so at the time. An earlier patent covering both square-socket- and triangle-socket -drive wood screws, U. These screws can be driven with standard Robertson bits.