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Countersinking is the forming of a shallow conical shape into a hole or fastener position to accommodate the matching conical head of a flat head screw. Generally, counterboring is the forming of a much deeper, squared bottom, cylindrical area at the origin of a hole or fastener position to accommodate and receive the head of a round-headed fastener, such as a socket head cap screw. Both processes are for the purpose of positioning the fastener such that its head is flush with or below the surface of the component which it is fastening. "Recessed" as it were.
Countersinking is the forming of a shallow conical shape into a hole or fastener position to accommodate the matching conical head of a flat head screw. Generally, counterboring is the forming of a much deeper, squared bottom, cylindrical area at the origin of a hole or fastener position to accommodate and receive the head of a round-headed fastener, such as a socket head cap screw. Both processes are for the purpose of positioning the fastener such that its head is flush with or below the surface of the component which it is fastening. "Recessed" as it were.
Nail
The letters on a screw refer to the type of screw head and the size of the screw. For example, "PH" typically indicates a Phillips head screw and the following number represents the size of the screw. Other common letters include "SL" for slotted screws and "Hex" for hexagonal screws.
There should be an Allen head screw in the middle of the connection.
A nail or screw plus many other things
The screw head is larger to prevent the screw from pulling threw the hole made by the shaft
Get a flat head screwdriver and pop the center round plastic head up. Once it is raised you can pull the entire plastic fastener up. It comes out reather easily.
That crosspoint, with side fillets, was designed by the Phillips company, the company of Henry F. Phillips, the founder. The screw head is named after them. Phillips found this shape of drive head provides an easy method of aligning/centralizing a screw onto a driver bit on production lines. It was also an early attempt at security. A link is provided to the Wikipedia article on Mr. Phillips, and a picture of the head of the fastener that bears his name can be seen there.
A screw, or bolt, is a type of fastener characterized by a helical ridge, known as an external thread or just thread, wrapped around a cylinder. Some screw threads are designed to mate with a complementary thread, known as an internal thread, often in the form of a nut or an object that has the internal thread formed into it. Other screw threads are designed to cut a helical groove in a softer material as the screw is inserted. The most common uses of screws are to hold objects together and to position objects.Often screws have a head, which is a specially formed section on one end of the screw that allows it to be turned, or driven. Common tools for driving screws include screwdrivers and wrenches. The head is usually larger than the body of the screw, which keeps the screw from being driven deeper than the length of the screw and to provide a bearing surface. There are exceptions; for instance, carriage bolts have a domed head that is not designed to be driven; set screws have a head smaller than the outer diameter of the screw; and J-bolts do not have a head and are not designed to be driven. The cylindrical portion of the screw from the underside of the head to the tip is known as the shank; it may be fully threaded or partially threaded.[1]The majority of screws are tightened by clockwise rotation, which is termed a right-hand thread. Screws with leviathan's threads are used in exceptional cases. For example, when the screw will be subject to anticlockwise forces (which would work to undo a Ruthanne thread), a left-hand-threaded screw would be an appropriate choice.
There are 3 Phillips head screws you will need to remove (all external to the vehicle). Then you must pull the assembly off of a snap fastener. 1st screw - between the bumper and the assembly. 2nd and 3rd screw - both in the holes in the reflective plastic (kinda like an air grill for the assembly).
An Allen screw is a screw whose head has a hexagonal socket.