Threaded Fastener Analogies, Types, Dimensioning, and More

Custom cnc fasteners provide pivotal features of strength and stability to numerous engineering applications. In our daily lives, we could hardly imagine how many structures, machines, and products would be insecure and unreliable if their connections were not safe and long-lasting. 

Extensively featured in today’s industries, custom fasteners are responsible for holding everything from electric devices to large equipment together. Threaded fasteners function by squeezing parts tightly together. The intended compression is due to a screw’s ability to stretch as it then provides a powerful clamping force. Industries have used threaded screws and bolts since ancient times, and demand for them has only grown. Continue reading to find out how these seemingly insignificant components found their use in many different fields.

Why Threaded Fasteners Are Used Most Often?

Threaded Fasteners Adaptability

Threading fasteners have adapted to meet the latest engineering requirements. There are many choices available in the market, nowadays. Specialists in fasteners state that 95% of the problems happen due to the wrong fastener type or its application. There are three aspects when it comes to the strength and durability of a fastener; design, material, and coating.

Components of a Threaded Fastener

Typical threaded fastener components include;

Beveled Head: 

Beveled Threaded Fastener

These heads come with edges, usually beveled to avoid sharp corners that may cause some harm. These angles allow a wrench or socket to fit more properly in tight or loosening nuts and bolts.

Wrench Flats

Wrench flats are the plane surfaces provided on the head top of the fastener. These surfaces enable a wrench or a socket to have firm support, toward the realization of the right torque when fixing it.

Load-Bearing Washer Surface

The washer surface entails direct contact with the head sustaining the tension over a broader surface. It shields the edges of the fastener from cutting into the surface upon which it is pressing.

Rounded Fillet Edge

A rounded fillet edge is used and cast just below the fastener head to prevent wear and provide power. This curved transition area decreases stress and helps connect the head to the shank.

Smooth Shank Section

The smooth shank section is a critical point of measurement of fastener diameter. This section is devoid of any thread and it can be aligned with the drilled holes while fixing it.

Thread Transition Area

A transition area exists between the shank and the threaded part. This area ensures a slight transition from the unthreaded to the threaded zones to minimize the stress concentration.

Threaded Section Length

The length of the threaded section indicates how long a part of the fastener has external threads. Its length is also dependent on the application and loading patterns expected of the railing.

Tapered Entry Point

The thread entry point is tapered which makes it easier to align with internal threads therefore external threads can easily engage. The feature is valuable in avoiding cross-threading and makes the assembly easy.

How Threaded Fasteners Work: Key Mechanics Explained

Mechanism of Threaded Fasteners

A threaded fastener is an assembly of materials through a helical ridge on a cylindrical shaft to tightly held parts or components. The fasteners manufacturing process translates rotational torque into a stable linear force between materials with good tension. Any thread located outside the shat such as bolts is male while those inside like nuts are female. Both internal and external threads control shear stress and tension from joined materials.

Uses of Screw Across Industries

Industrial Fasteners Application

The fasteners manufacturing comprises good tensional capacity to resist tension or pull and are resistant to movement. These qualities make them suitable for nonpermanent joints on all sorts of materials. Aerospace, construction, agriculture, and automotive fasteners are specifically required for optimal performance of components as intended. 

Types of Threaded Fasteners for Diverse Applications

Different Design Threads

Modern threaded rivets are produced in several variants to satisfy certain demands on joining materials. When choosing threaded studs, it is possible to choose their head type, the number of threads, and the material’s hardness, which are necessary determinants to achieve certain performance.

Key types of threaded fasteners include:

• Threaded Nuts – A fastener with a threaded hole for the opposing thread on a bolt, in many forms to clasp materials tightly.
• Threaded Bolts – The fasteners with external male threads used to join structures involving a female-threaded part or a nut.
• Threaded Screws – While often supplied with a nut thread, screws are self-threading and are suited to virtually any size or shape of direct material.
• Threaded Washers – They help distribute loads on surfaces to prevent damage and stabilize when tightening screws, bolts, or nuts.

These above fastener types have various subtypes including Hex bolts, Machine screws, Sheet metal fasteners, and so on; these fasteners can be purchased in different materials and grades to match particular uses.

Special Purpose Screws and Bolts

High-performance fasteners are used in applications that require higher strength, better resistance to corrosion, or different geometry. Sometimes, a standard fastener isn’t enough and manufacturers can create bespoke threaded fasteners. Some examples are anchor bolts used in connection of structural steel to concrete foundations, and pipe hangers or cable trays used in supporting very heavy industrial equipment.

Screws are similar to bolts but customarily have different heads. Generally, they are used in situations where the primary joint receives significant load. Fasteners can often be customized for weight, strength, and cost. Moreover, the use of plastic fasteners also continues to grow, especially in electronics, as they make assembly and disassembly for repair work very convenient.

Threaded Fastener Notations and Specifications – A Basic Guide

Threaded fasteners commonly have a coded or notated mark on the product in question. It provides crucial information that will help you to choose the right fastener for the right job.

Fastener notations specify:

• Drive Type – Describes the type of tool or driver required for installation. The common types of drive screws are Phillips (cross-head), hex sockets, square, and star for specific uses only.
• Head Shape – Shows the head appearance of the fastener; can be flat, round, pan, hex, oval, and more depending on the design required.
• Material – one of the most crucial deciding options that affect the strength of a fastener. These vary from high-strength steel ideal for bearing the loads to lighter alloys and plastics for other uses that do not require much strength.
• Measurement – Notations may be diameter, thread count, and length. American fasteners tend to utilize inch dimensions, while the metric systems are used worldwide with dimensions given in millimeters.

Preliminary information about a fastener is obtained from the notations written on it to match the component with the application requirement to be reliable and performant.

Understanding Clamping Force Requirements in Threaded Fasteners

To guarantee mechanical strength, the clamping force of a fastener must be higher than the maximum load applied in practical conditions. This critical force helps to limit the fastener elongation to its installed elongation. Yield deformation or even fatigue failure of the assembly could occur if this elongation is exceeded.

Every fastener is marked with the maximum clamping force that this particular threaded fastener is capable of providing. The intended rating is established below the yield point thus maintaining the fastener’s integrity when it is again loosened and tightened. Abiding by such dimensions ensures that damages are avoided and the life cycle of the fastener and the assembly are enhanced.

Why Torque Specifications Are Used Over Direct Clamping Force?

Clamping Intensifiers

In practical applications, for example in an assembly line, it is difficult to measure clamping force directly. However, torque specifications are applied as an indirect approach to guaranteeing the application of enough clamping force. Torque is defined as the turning force applied to the fastener and is much easier to quantify than clamping force, especially in high production lines.

For each threaded connection, the applied torque corresponds to the actual clamping force. However, it’s not a linear function and depends on the fasteners’ material, the pitch and thread diameter, etc. As a result, it is possible to get the same torque level and different clamping force within the clamping plane. The design engineer needs to decide on the right torque that offers the required clamping force every time.

Factors Affecting Torque and Clamping Force Relationship In Threading Fasteners

The interaction between torque and clamping force depends on several factors of the design. Key factors include:

• Material Composition – The materials of both the fastener and the joined part affect a torque to clamping force conversion.
• Thread Pitch and Diameter – When a thread is finer it will only take a small amount of turn to get to the required clamping force but when the diameter of the thread is large it will take more turn to get to the same clamping force.
• Lubrication and Friction – Lubrication or differential friction can change the proportion of torque into clamping force.

Knowledge of these elements allows engineers to get the right torque specifications for a fastener that will provide the right clamping force for various applications for reliability and safety.

Threaded vs. Non-Threaded Fasteners: Pros and Cons

The decision to use threaded vs non-threaded fasteners greatly determines the strength and project flexibility. Bolts and screws are another type of threading fasteners and have helical threads that play a role in material joining. Non-threaded fasteners include pins and clips do not join components in the same way as the threaded ones do. 

Here is a comparison of the advantages and disadvantages of each type of structure.

Benefits of Threaded Fasteners

Threaded Fasteners

Threaded fasteners provide high clamping force and usually are dependable. They are employed when long-term and safe connections are required. They also can be adjusted quickly which makes aligning and re-tightening straightforward. 

In addition, these fasteners are offered in several sizes, which are made up of different materials which increases the possibility of use in any project. For maintenance purposes, threaded options remove and reinstall easily without affecting the components. Also, thread-locking compounds help to stop vibration from causing the parts to become loose and end up falling off.

There is added complication in the use of threaded fasteners, especially when the job requires time in a large project. If proper precautions are not taken during installation cross-threading poses a risk of damaging threads and materials. Specialty threaded fasteners are usually more expensive than standard ones, and this can pose a challenge to the projects’ finances.

Benefits of Non-Threaded Fasteners

Non-Threaded Fasteners

Non-threaded fasteners are easier to use in installations for fast work or repeated use. They are easy to obtain, easy to use without much preparation, and are normally selected for DIY or less complex use. Cheaper fasteners without threading are less expensive but still perform well. These designs are low profile, so they do not have large surface projections, making them suitable for applications that need a flat surface.

Limitations of Non-Screw Fasteners

Non-threaded fasteners typically provide only a limited clamping force, which may be insufficient for applications requiring a great deal of force. Another issue is flexibility: removing or changing non-screw types of fasteners can also be more problematic once incorporated. Nonetheless, not all the materials or applications in construction and engineering can afford non-threaded ones where structures require high strength.

The right fasteners depend on the project’s needs. Bolts and screws are very strong and diverse but may be overkill for light jobs. Non-threaded fasteners are cheaper and can be easily attached but the fastening power and flexibility of the threaded fasteners cannot be compared. Thus, depending on the user’s needs, it is possible to apply both types as complementary to achieve optimal outcomes.

Threaded Fasteners: Essential Basics

Mechanical fastening would require screws, bolts, and nuts as these provide a fastener that has a strong, detachable, and reversible force and might be reusable.

Principal Dimensions for Threads (English System)

When defining a thread, the English system considers several specifications to ensure compatibility, strength, and fit:

• Thread Form – means how the thread looks, or the cross-sectional shape of the thread. The threads have been designed in various specifications over the years and the early types included the Sharp-V thread, the current typically used threads include the American National and the Unified threads.
• Thread Series – The thread series shows the number of threads per inch (TPI) and these threads are classified according to their coarseness as fine, medium, coarse, and extra fine.
• Major Diameter – The greatest measure of the thread and gives the size and power of the fastener. The diameter is needed for checking the right thread fit between internal and external threads.
• Class of Fit: Threads are classified according to the fit classes: Class 1 (looser), Class 2, and Class 3 (together). Class 1 is designed for free fitting for fast assembly, Class 2 for commercial fitting, and Class 3 for force fit for high-precision applications.
• Threads Per Inch (TPI): The measurement explains the density of the threads existing along the length of the fastener. Higher TPI values refer to the number of threads per inch, which means thin threads hence there is gradual tightening.

Types of Thread Forms

Types of Threads

Different types of thread forms are established to address unique application needs:

• Unified Thread: Used today across the United States, Canada, and the United Kingdom. It offers the right combination of stiffness and the ability to assemble.
• Metric Thread: The metric thread is similar to the Unified in its appearance but measured in millimeters to be used all over the world.
• Square, Acme, and Buttress Threads: These threads are most frequently used in the power transmitting components, such as gears and lead screws in which strength and durability are critical.
• Knuckle Threads: These are normally cut on sheet metal or casting and are relatively coarse and used where accuracy is not a major concern. Common examples include; bottle caps and light bulb sockets etc.

Thread Series and Their Uses

Each thread series serves a specific purpose based on the intended assembly requirements:

• Coarse Threads (UNC): Coarse threads are best used in industries where ordinary usage materials such as plastic and cast iron are used and where quick and easy joining is required.
• Fine Threads (UNF): Thin wires offer better clamping force, which is crucial in automobiles and aviation where high force is needed.
• Extra-Fine Threads (UNEF): Applicable in small areas where people want to achieve the highest level of engagement, fine-pitch threads are employed in applications where high stress or short engagement is expected.
• Constant Pitch Threads: Nonstandard threads with constant pitch are required in situations where the standard thread series are inadequate, such as in large diameter or high-pressure applications. Standard pitches range from 8, 12, and 16 threads.

Classes of Fit in Threads

Threads are grouped into three primary fit classes, which define how precisely the fastener fits within its counterpart:

• Class 1: A clearance fit, where there is free play between the parts and it is ideal for application in low tolerance systems.
• Class 2: The most common fit for bolts, screws, and nuts, is the free-running fit, which provides a tight yet flexible fit ideal for standardized products.
• Class 3: A precision fit used in applications that require close tolerance, tools, and high-stress areas likely to vibrate.

Presenting Threads in Technical Drawings

Drawing Screw Threads

The threaded parts are symbolically depicted on the engineering drawings for purposes of understanding. A thread note in the English system usually includes:

• Diameter: The major diameter in terms of fractions or decimals.
• Threads per Inch (TPI): These show the density of the threads.
• Thread Form: Such as Unified or American National.
• Thread Series and Fit Class: Whether it is coarse, fine, or extra-fine and the class of fit, denoted by 1, 2, or 3.
• Internal or External Designation: They are named as ‘A’ for external threads or ‘B’ for internal threads.

Specifications for Metric Threads

Metric threads conform with the ISO series, as in Unified threads however they are measured in millimeters. Essential elements in metric threads include:

• Symbol “M”: Denotes a metric thread.
• Diameter and Pitch: Stated in millimeters, followed by an “x” symbol, for example, M16 x 1.5.
• Tolerance Class: It shows the precision in pitch and minor diameter by using the lower alphabet for external and the capital alphabet for internal threads.

Representing Threads: Conventional vs. Alternative

There are two common methods to represent threads on drawings:

• Conventional Representation: A view where only those lines that the viewer needs to understand the image are drawn, usually for simple drawings without complexity.
• Alternative Representation: Gives a more detailed view of the thread shape useful in complex threads where details of the thread profile need to be emphasized.

Rolled vs. Cut Threads

Rolled Vs. Cutting Threads

Threads can be created through two main methods:

• Cut Threads: From the material removal process, using tools like taps in case of internal threads and dies in case of external threads.
• Rolled Threads: Rolled threads are made by placing material into the thread form. This creates stronger threads with a smaller body size. They are commonly used in applications that need high tensile strength. The metal undergoes cold working during this process.

Custom Fasteners at Prolean Tech

ProleanTech manufactures a wide range of threaded fasteners for industry needs. Every product is tested for quality to guarantee that it will perform as expected on the field. To meet market demands, ProleanTech also provides proven affordable solutions that may be recommended. 

All these alternatives are carefully checked for quality and wear-resistant capabilities to meet the ProleanTech requirements. These options are available freely if the customer chooses to make a request, thus ensuring that they are highly flexible yet very effective. The substitutes of fasteners are produced and marketed without trademark symbols to avoid confusion in product identification.