Industrial screws are available in a wide variety of head styles, whether the head style serves a functional purpose or it's purely decorative. The primary difference in head styles is whether the head is countersunk, where the head mounts flush into the substrate, or non-countersunk, where the head remains visible after installation.
Bugle Head Screws
Bugle head screws are a variation of countersunk screw heads, but the underside of the head is curved, like a bugle. This feature reduces damage to plasterboard substrate, which is why bugle head screws are commonly used in drywall applications.
Flat Head Screws
Flat head screws are designed so that the screw in countersunk and sits flush with the surface being fixed, in order to assure that the head will not catch.
Undercut Flat Head Screws
Differing from the conical underside of the head that tapers down to the shank in standard flat head screws, undercut flat head screws feature a flat bottom under the head. An undercut flat head screw has 100% contact with the countersunk hole, and will sit slightly more flush than a standard flat head screw.
Hex Washer Head Screws
Often seen in sheet metal screws and lag bolts, hex washer heads feature a standard hex head with an integrated, immovable washer for larger bearing surface. Hex wash heads are sometimes slotted so that they can be installed with either a wrench or a flat bladed screw driver.
Oval Head Screws
Oval head screws are a combination of a countersunk head and a domed head. Largely used as a decorative feature, the screw is countersunk but the top of the head still protrudes above the surface.
Undercut Oval Head Screws
Like in undercut flat head screws, undercut oval head screws feature a flat bottom under the head, instead of the conical underside of the head that tapers down to the shank in standard oval head screws, which allows the screw head to have 100% contact with the countersunk hole.
Pan Head Screws
One of the most common types of screws heads, pan head screws provide a larger bearing surface, making them ideal for applications where the screw head does not need to be flush to the surface of the substrate.
Round Head Screws
Round head screws are similar to pan head screws, with the exception of the straight sidewall part of the head. In round head screws, the entire surface of the screw head is domed.
Round Washer Head Screws
Round washer head screws feature a built-in, immovable washer to create a much larger bearing surface and better resist pull-out problems. These screws usually have a phillips drive, but can be sourced with other drive styles if necessary.
Truss Head Screws
Also known as oven head, stove head, and oval binding head, truss head screws feature wide, low profile heads that can cover larger diameter clearance holes in applications when additional play in assembly is required.
The screw's thread is the uniform helix-shaped ridge on the external surface of the cylinder, a sloping plane curled around a cylinder. Different thread types are generally specified per substrate or application, and can depend on different factors, such as thread pitch, thread angles and thread cutting.
Type A Thread Screws
Type A thread screws are thread forming screws used with drilled, punched or nested holes in thin metal.
Type AB Thread Screws
Type AB thread forming screws combine the locating point of Type A threads with thread size and pitch of Type B threads. These screws are subject to the standard limitations of Type B screws.
Type B Thread Screws
Unlike Type A thread screws, Type B thread screws are for use in heavier metal, usually between .050 and .200 thick. Featuring a larger root diameter and a finer thread pitch, Type B screws are used in heavy sheet metal, plastics and more.
Machine Screws
Machine screw thread features more threads per length than any other thread type, creating superior fastening strength between a machine screw and it's mating partner, usually a nut.
Tri-Lobe Thread Screws
In tri-lobe thread screws, three vertexes perform a roll-forming process to form mating threads. This creates better thread forming properties than Type C or Type CA screws, plus drives with less torque.
Self-Drilling Thread Screws
Self-drilling screws create mating threads as they are drilled, and can come in either fine or coarse threads. Self-drilling screws are also self-tapping screws (meaning they "tap" a thread as they drill), but not all self-tapping screws are self-drilling screws.
Type 17 Thread Cutting Screws
Type 17 thread cutting screws are used in wood and feature a coarse tapping screw thread with an especially long, sharp point that has been fluted to capture chips.
Type 25 Thread Cutting Screws
Similar to Type 23 but instead with coarse threads, Type 25 thread cutting screws are used in plastics and other soft materials with large chip clearing and cutting surfaces.
Type F Thread Cutting Screws
Type F thread cutting screws feature machine screw threads and a blunt tapered point, making them ideal for heavy gauge sheet metal, cast iron, brass and plastic.
Type 23 Thread Cutting Screws
Type 23 thread cutting screws are in the fine thread series and offer maximum thread cutting area and excellent chip clearing, all with minimum tightening torques.
A screw drive is a system of shaped cavities and protrusions on the screw head that allows torque to be applied to it. Generally, the screw drive also requires a matching mating tool like a screwdriver to turn it.
Slotted Drive Screws
Slotted drive screws have a single slot in the fastener head and is driven by a flat-head screwdriver. These were the first type of screws ever invented, and for a long time were the most common and cheapest to make.
One-Way Drive Screws
One-way drive screws can only be turned in one direction. Often used in applications where security is of high importance, they can be installed with a standard flat-blade screwdriver, but cannot be easily removed using standard tools.
Phillips Drive Screws
Phillips drive screws were developed as a solution to the problems with slotted screws; easy cam out, precise alignment required to avoid slippage and damage to driver, fastener, and adjacent surfaces, and difficulty of driving with powered tools.
Phillips Slotted Drive Screws
Phillips slotted drive screws are "combination screws", meaning they can be used with either a Phillips head screwdriver or a flat head screw driver.
Square Phillips (Quadrex(R)) Drive Screws
Square Phillips drive screws are also known as Quadrex screws, and feature a combination of the Phillips and Robertson (Square) screw drives. While either a standard Phillips or square tool can be used, the dedicated square phillips tool increases the surface area between the tool and the fastener so it can handle more torque.
Square Drive Screws
Square drive screws, also known as Robertson screws, have a square-shaped socket in the screw head and a square protrusion on the tool, both of which have a slight taper.
6 Lobe (Torx(R)) Drive Screws
Torx(R), star or 6 lobe drive screws feature a star-shaped recess with six rounded points. Due to the shape of the 6 lobe socket, Torx(R) drive screws can withstand high torque tension without camming out, making them ideal for use in electronics and automotive applications.
Hex Socket Drive Screws
Hex socket drive screws have a hexagonal recess in the head and can be driven by an Allen wrench or by a hex screwdriver bit. Tamper-resistant versions with a pin in the recess are available for applications where security is a concern.
Hex Drive Screws
A hex drive screw, also known as a hex cap screw, features a six-sided head and can be turned with and adjustable wrench, a combination wrench, or a hex driver bit.
Spanner Drive Screws
Spanner drive screws, also known as Snake-EyesTM screws, have a drive uses two round holes opposite each other in order to to prevent tampering. These screws are commonly used in restroom partitions and elevators, but are also sometimes found in solar panel installations or other settings where theft may be an issue.