Did you know that the first known recorded use of screws occurred during the time of the ancient Greeks; they used them in devices to press olives and grapes. From those humble beginnings, screws have become one of the most widely used pieces of hardware manufactured today.
Fastener hardware comes in a wide variety of shapes, sizes, styles, and materials. One of the most important considerations when selecting a fastener for your application is what type of head the screw will have.
Here we give a brief overview of some of the most common screw head types along with their typical applications.
SOCKET HEAD CAP Socket head cap screws are machine screws with a cylindrical barrel shaped head containing a hexagonal socket to fit a wrench for turning rather than a slot or external hexagonal. These properties mean that socket head cap screws are well suited for use within confined spaces. Socket cap heads are smaller; hence, the size of the component parts can be reduced, reducing material costs. Smaller parts cost less to drill and tap, take less energy to drive, and weigh less than alternatives.BUTTON HEAD SOCKET CAP Button head socket cap screws have a rounded, low-profile head containing a hexagonal socket to fit a wrench for turning rather than a slot or external hexagonal. These properties mean that Button head socket cap screws are well suited for use within confined spaces. Due to their flush profile these types of screws are ideal for areas with very little overhead or clearance. They are best used in light duty applications, such as removable panels, however their wider bearing surface and high tensile strength make them a reliable choice for some security applications as well.SOCKET SET SCREW Socket set screws are a type of screw generally used to secure an object within or against another object. The most common examples are securing a pulley or gear to a shaft. Socket set screws are headless, meaning that the screw is fully threaded and has no head projecting past the major diameter of the screw thread. A socket set screw contains a hexagonal socket to fit a wrench for turning rather than a slot or external hexagonal. Fastening for these components requires no external clearance. These properties mean that socket set screws are well suited for use within confined spaces. The socket set screw passes through a threaded hole in the outer object and is tightened against the inner object to prevent it from moving relative to the outer object. It exerts compressional or clamping force through the bottom tip that projects through the hole.FLAT HEAD SOCKET CAP Flat head socket cap feature a low-profile and countersunk head. They are ideal for applications requiring a strong fastener with a flush mount. They are often used in projects that require moving parts to pass over a fastened area. Because of their ability to mount flush with the surface, they are less apt to snag objects moving overhead. Flat head socket cap screws are produced with a socket drive that contains a hexagonal socket to fit a wrench for turning.FLAT HEAD PHILLIPS Flat head Phillips screws feature a low-profile and countersunk head. They are ideal for applications requiring a strong fastener with a flush mount. They are often used in projects that require moving parts to pass over a fastened area. Because of their ability to mount flush with the surface, they are less apt to snag objects moving overhead. Flat head Phillips screws have two partial slots crossed at right angles and are driven by a special screwdriver called a Phillips screwdriver. One of the main advantages of the Phillips system is that the screw and screwdriver together are self-centering. The x-shape of the screwdriver head fits into the similarly shaped slot of the screw and is held in place so the force of the torque is naturally centered, ensuring that the screw is driven straight.FLAT HEAD SLOTTED With a low-profile and countersunk head, flat head slotted screws are ideal for applications requiring a strong fastener with a flush mount. They are often used in projects that require moving parts to pass over a fastened area. Because of their ability to mount flush with the surface, they are less apt to snag objects moving overhead. A flat head slotted screw is manufactured with a slotted head drive. Slot screw heads have a single horizontal indentation, referred to as the slot. The fastener head is driven by a common blade or flat-bladed (flat head) screwdriver. The slot has a flat bottom and are good for low torque low speed applications.PAN HEAD PHILLIPS Pan head Phillips screws take their name from the appearance of their head, which looks similar to an upside-down frying pan. Pan head Phillips screws are a common head type of non-countersunk screw head used in machine screws. They have wide heads, a flat bearing surface, high vertical, chamfered, or curved sides, and a flat or slightly domed top. A pan head Phillips head has two partial slots crossed at right angles, driven by a special screwdriver called a Phillips screwdriver. One of the main advantages of the Phillips system is that the screw and screwdriver together are self-centering. The x-shape of the screwdriver head fits into the similarly shaped slot of the screw and is held in place so the force of the torque is naturally centered, ensuring that the screw is driven straight.PAN HEAD SLOTTED Pan head slotted screws take their name from the appearance of their head, which looks similar to an upside-down frying pan. Pan head slotted screws are a common head type of non-countersunk screw head used in machine screws. They have wide heads, a flat bearing surface, high vertical, chamfered, or curved sides, and a flat or slightly domed top. A pan head slotted screw is manufactured with a slotted head drive. Slotted screw heads have a single horizontal indentation referred to as the slot. The fastener head is driven by a common blade or flat-bladed screwdriver. The slot has a flat bottom and are good for low torque low speed applications.FILLISTER SLOTTED Fillister head slotted screws have a large oversized head and are the preferred head type for counterbored holes. They are similar to a pan head slotted screw but with greater side height. Fillister head slotted screws, also known as raised cheese head slotted screws, are similar to cheese head slotted screws because both have cylindrical sides and a flat mating surface. While the cheese head slotted has a flat top, the fillister slotted screw head has a domed top resulting in an overall deeper head. A fillister head slotted screw is manufactured with a slotted head drive. Slot screw heads have a single horizontal indentation referred to as the slot. The fastener head is driven by a common blade or flat-bladed (flat head) screwdriver. The slot has a flat bottom and are good for low torque low speed applications.CHEESE HEAD SLOTTED Cheese head slotted screws have cylindrical sides with a flat disc top and a flat bearing surface. They are defined by their head type the head height is approximately half of its diameter and features a slot drive. The name cheese head is derived from the similarity in shape and proportion to that of a wheel of cheese. Fillister head slotted screws, also known as raised cheese head slotted screws, are similar to cheese head slotted screws because both have cylindrical sides and a flat mating surface. However, while the cheese head slotted has a flat top, the fillister slotted screw head has a domed top resulting in an overall deeper head. A cheese head slotted screw is manufactured with a slotted head drive. Slot screw heads have a single horizontal indentation referred to as the slot. The fastener head is driven by a common blade or flat-bladed (flat-head) screwdriver. The slot has a flat bottom and are good for low torque low speed applications.HEX HEAD Hex head screws, also known as hex bolts, are bolt fasteners with a six sided hexagon head and externally threaded body. The hexagonal head profile enables easy wrenching while putting enough torque to the bolting joint. Hex bolts are generally used with a washer and hex nut assembly, or a tapped hole. Hex cap screws allow for greater torque than that of traditional screws with a circular head.TWELVE POINT-FLANGE HEAD CAP SCREWS Twelve point flange head cap screws, also known as 12-point bolts, are an alternative head design for hex socket cap screws. The flange diameter and head height are designed to fit a range of applications and counterbored holes designed for standard hex socket cap screws. The 12-point design permits this style bolt to be tightened down with a 12-point socket wrench, which permits higher torque to be applied as compared to a standard internal hex drive socket head cap screw. Another advantage of the 12-point head type is their use in tight spaces. The 12-points have 30° between flats (as opposed to Hex heads which have 60°). This enables increased wrench flexibility (or placement) when manipulating the fastener.What does UC Components, Inc. offer?
As a manufacturer of precision-grade screws we give engineers more flexibility to choose the head type, shoulder length, thread length, and any other variable that would best fit their application. Please download our part and head type identifier document here. Our vented fasteners are available in a wide range of Metric and Inch-measure sizes and lengths. We also offer a variety of finish options to suit any need.
How can fasteners from UC Components, Inc. help you?
UC Components, Inc. has been the world leader in high vacuum hardware since . While the right head type, length, material, coating, plating, or finishing treatment for your fastener application is best defined by your process engineer, we are always here to assist you.
We offer a variety of standard and vented screws, washers, and hex nuts, numerous finish options, along with specialized venting designs, complete custom product development, and Class 100/ISO Class 5 Cleanroom cleaning & packaging. View our parts catalog online to find the components you need, request a quote, or contact us for more assistance or additional information. If you do not see the items that you need listed in our standard products, please give us a call! We may not stock it but we are happy to acquire and manufacture just about any fastener or O-ring that you need.
Whatever your engineering or manufacturing application is, its likely that youre well-acquainted with screws of various types. However, as often as you may have used screws, you may still be unfamiliar with their components.
Understanding key screw components is essential when you have to decide which type of screw to employ for a specific function. And when there are so many options available, that understanding becomes even more important.
This article will help, as it outlines the anatomy of a screw and describes the various types, styles, and functions of each part.
Screws consist of five key components: head, shank, threads, drive, and tip. Below is a diagram that shows where each component is located, followed by descriptions of their core functions.
The head of a screw is its topmost part and serves as the primary contact point for tools during installation. There are many different types of screw heads and drive types (which well cover later in the article).
You can also categorize screw heads by being countersunk or non-countersunk. Countersunk is when the head rests evenly with the material surface after installation. Non-countersunk is when the head protrudes the material surface after installation, leaving the head exposed.
Regardless of which you select, your choice of screw head is critical, as it determines the tool required for installation/removal and impacts efficiency, torque transmission, and installation/removal accessibility.
The shank refers to the main body of the screw, which connects the head to the tip. It has a pivotal role in determining the screws load-bearing capacity and resistance to shear forces. The shanks length and diameter vary depending on the application, ensuring optimal strength while considering space constraints. Additionally, the shank may feature unthreaded portions, known as the shoulder or body, for specialized applications.
Threads are the distinctive ridges spiraling around the shank of a screw, responsible for creating a strong and secure connection. They engage with the mating surface, generating friction and preventing the screw from loosening under load.
There are various standards used to define thread characteristics. In the United States, we most commonly use the Unified Thread Standard (UTS), which is controlled by the American Society of Mechanical Engineers (ASME). UTS dictates standards only for inch threads, not metric.
Some of the most popular UTS thread series are UNC, UNF, and 8-UN. They each have different thicknesses from fine to coarse and, therefore, different performance capabilities.
Want to read more about fastener threads? Jump to this article.
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The drive is what determines which type of screwdriver or fastening tool must be used to install and remove a screw. There are two main types:
require a tool that inserts into the screw head, like a screwdriver. Phillips, slotted, and socket heads are some internal drive examples. Heres a photo of a wood screw with one. We dont manufacture these here, but its a good example of an internal drive:
require a tool that wraps around the screw head, like a wrench. Hex, hex flange, and square heads are some external drive examples. Heres a photo of one:
Located at the opposite end of the head, the tip, or point, initiates contact with the material being fastened. Different point designs cater to specific applications.
For instance, self-drilling tips enable screws to penetrate metal without the need for pre-drilling, saving time and effort. Self-tapping tips create their own threads in materials like wood or plastic. Sharp tips are ideal for precise placement in delicate applications.
Some screws dont have tips or points but rather a blunt end. These are more common in the manufacturing space and are generally used with a pre-tapped hole.
Besides the anatomy of a screw, there are a few other things to keep in mind before deciding what is best for your application.
Its common for people to misunderstand the differences between bolts and screws or not realize that one exists in the first place. But there are differences it just depends on who you ask.
In this previous article of ours, we discuss one government agencys opinion on the matter and give some qualifying criteria that set the fasteners apart.
The key to measuring screws is knowing the key components and measurement terminology. If youve read through this article up until now, youve already familiarized yourself with one set of that information.
Next up is measurement terminology. Heres the most important of it.
The distance from the flat part of the head to the point or blunt end of the screw.
The distance from the crest (top) of the thread on one side to the crest of the thread on the other side.
The distance from the root (bottom) of the thread on one side to the root of the thread on the other side.
The diameter of a theoretical cylinder that exists halfway between the major and minor diameters.
The estimated major diameter. Its just the major diameter, rounded up or down to the nearest whole number.
The distance from a point along one thread to the same point on the next thread.
Learn more about this terminology and how to measure screws in this article.
Looking for a special screw? Were here to help. Check out our custom fastener manufacturing capabilities sheet to see if your screw specifications are in our wheelhouse, then request a quote from us to get your project started.
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