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This is a slotted head screw.

The slot screw drive has a single slot in the fastener head and is driven by a “common blade” or flat-bladed screwdriver. It was also the first type of screw drive to be developed, and for centuries it was the simplest and cheapest to make. The slotted screw is common in simple woodworking applications, but is not often seen in applications where a power tool would be used because a power driver tends to slip out of the head, potentially damaging the surrounding material. The tool used to drive a slot is called a common blade, standard, flat-blade, slot-head, flat-tip or flat-head / flathead screwdriver.

Slotted head screws are more cheaper and easy to make, and they’re a good choice for applications that require the screws to be turned by hand. Cabinetry and furniture making are two areas where slotted head screw drives can be commonly found.

But unfortunately, slotted head screws aren’t very useful when it comes to electric screwdrivers. With so much power from the electric screwdriver, the screwdriver will slip right out.

 

This is a Philips head screw.

The main point of the Phillips head was to provide a better contact with the screwdriver than the original flat head, because the flat headed screw driver often tended to cam-out cause damage to the screw head, The Phillips head was designed to solve this problem by changing the design from a single groove to a simple cross to improve contact and torque, the design was then patented in 1930’s. The design of the head was actually designed to also improve cam-out to stop the aluminium threads stripping from the screw when assembling aluminium aircrafts as assemblers often excessively tightened the screws so tight that the threads of the screws stripped off. The design off the screw head was to accept a driver that had a 57 degree point with tapered wings that came to a sharper point, this enabled the driver to be released from the screw when excessive torque was applied.

 

The Pozi-drive was invented to further improve on the torque and cam-out of the Phillips head. To do this there was a second cross added on to the first cross. This will not only help when distinguishing between the two head types, it also further improved the contact of the driver to the screw. A different screwdriver is needed for use with each screw. The new screwdriver for use with a pozi-drive screw has a blunt point rather than a sharp point and the angle of the blades are sharper by 45 degrees. The driver doesn’t have rounded corners like the Phillips driver has. The design was patented in the 1960’s by the American Screw Company and the Phillips Screw Company as a joint venture and the name is thought have come from an abbreviation of “Positive Drive”.

One of the most common problems with the screws are that to the untrained eye both recesses look the same. A Phillips Driver will fit into a Pozi screw head but a Pozi driver will not fit into the Phillips screw head, it is not recommended to use a Phillips driver with a Pozi screw as it will eventually round off the recess of the head causing damage to the screw and making it unusable.

 

This image is a sample colour of Zinc Plated

Corrosion Protective Coatings –

Zinc Plated

The most economic and common fastener finish, comprising a thin coating of zinc applied either by electroplating or mechanically. A shiny silver grey appearance, it will normally be enhanced by a chemical chromate passivation conversion which applies a harder surface film. This can be clear (bluish tinge), or iridescent yellow which is thicker and gives marginally better protection.

Clear is referred to as zinc, zinc clear, blue zinc.

Yellow is referred to as zinc plate gold (ZPG), zinc yellow chromate (ZYC), zinc di-chromate, zinc yellow pass.

Sample colour of Cadmium Plated

Cadmium Plated

Formerly a popular electroplated or mechanically applied finish, looking like but giving slightly better protection than zinc and providing increased lubricity; also chromate converted. Very seldom used today due to its toxicity and environmental non-acceptability. If specified, it is usually through habit, error or ignorance and possible confusion with zinc.

 

Sample colour of Galvanised

 

Galvanised

A very heavy coating of zinc applied by hot dipping in a bath of molten zinc, then centrifuge spinning for even distribution and removal of the excess, or mechanically cold welding a zinc powder in a barrel rumbling process. The hot dip finish is rougher and duller than electroplated finishes but because of the thickness achieved, gives considerably enhanced protection. Often it is wax coated to provide assembly lubrication.

 

Reference & Image:

Decks.com. 2018. New and Interesting Finds On Amazon. [ONLINE] Available at: https://www.amazon.com/Stainless-Machine-Binding-Slotted-Threads/dp/B00DD4FTP6. [Accessed 22 March 2018].

Decks.com. 2018. Industrial Fasteners & Components. [ONLINE] Available at: http://www.fastenercomponents.com/news/screw-head-screw-drive-types/. [Accessed 22 March 2018].

BSFixings.uk. 2018. The difference between Phillips and Pozi screw heads. [ONLINE] Available at: https://bsfixings.uk/the-difference-between-phillips-and-pozi-screw. [Accessed 22 March 2018].

www.jamesglen.com. 2018. Finishes and Coatings. [ONLINE] Available at: http://www.jamesglen.com.au/finishes-and-coatings/. [Accessed 22 March 2018].

[ONLINE] Available at: https://yechime.en.taiwantrade.com/product/zinc-coated-steel-sheet-galvannealed-zinc-iron-alloy-669793.html. [Accessed 22 March 2018].

www.jamesglen.com. 2018. Finishes and Coatings. [ONLINE] Available at: http://www.jamesglen.com.au/finishes-and-coatings/. [Accessed 22 March 2018].

OVERLAND METRIC. 2018. Full Kit | Gold Cadmium Plated | FJ40. [ONLINE] Available at: https://www.overlandmetric.com/products/full-kit-gold-cadmium-plated-fj40. [Accessed 22 March 2018].

www.jamesglen.com. 2018. Finishes and Coatings. [ONLINE] Available at: http://www.jamesglen.com.au/finishes-and-coatings/. [Accessed 22 March 2018].

Mindiamart. 2018. Mark as Favourite Galvanized Steel Sheets. [ONLINE] Available at: https://www.indiamart.com/proddetail/galvanized-steel-sheets-4437611291.html. [Accessed 22 March 2018].

 

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