Deck screws are bugle head screws with spaced threads, extra sharp points and a dacrotized finish. They are used for joining pieces of pressure treated lumber.
Drywall screws are bugle head screws with spaced threads and extra sharp points. They are used for attaching drywall to wood studs or to 25 gauge metal studs.
Machine screws are straight shank parts designed to bind metal to metal by going through an opening pre-tapped to form the same configuration as the threads of the machine screw. The thread runs the entire length of the shaft. Most machine screws do not have a point, although a header point model does exist.
Self-drilling screws (also known as tek screws) drill their own hole in thin sheet metal, heavier gauge metals and other materials; then form close mating threads in the hole.
Self-drilling screws are ideal for automated assembly and reduce or eliminate the need for drill bits or taps. Once the hole is drilled, self drilling screws tap the hole in the same way as thread forming or thread cutting screws do in a pre-drilled hole. They are also designed to eliminate paint build-up, weld flash, or foreign material that may occur in pre-drilled or pre-punched holes.
Self-piercing screws have the ability to self-pierce metallic material, form a sleeve by extruding metallic material, and tap their own mating threads when driven. Self-piercing screws are high-strength, one-piece, one-side-installation fasteners, with sharp point angles of 25 to 30 degrees.
Sems are machine screws and freely-rotating, captive washers manufactured as one assembly. Sems are usually used as locking screws, with the washer providing the locking action. Machine pre-assembly of these two parts may provide cost savings to the end user, especially in high-volume applications for machine screws.
Set screws are a type of screw generally used to secure an object within another object and is generally fully threaded.
Slotted set screws are tightened with a screwdriver; square head set screws are tightened with a wrench.
Tapping screws (also known as sheet metal screws) are threaded fasteners with the unique ability to “tap” their own mating internal thread when driven into preformed holes in metallic and non-metallic materials.
Because they form or cut their own mating thread, there is unusually good thread fit which enhances resistance to their loosening in service. Tapping screws can be disassembled and are generally reusable.
Thread cutting screws are tapping screws that have cutting flutes or edges at their point so that when driven into a preformed hole the screw acts as a tap and actually cuts its own mating thread. This, therefore, removes material as it is driven.
Thread rolling screws are tapping screws that form their mating internal thread by displacing material adjacent to the hole and pushing it outwards into the open spaces between the threads of the screw.
Thread rolling screws are best used in fairly thin sections of malleable materials, such as plastic or wood. Unlike thread cutting screws, thread rolling screws do not contain cutting slots and do not produce chips.