What is the difference between fastener strength grades and markings, and how can they be correctly understood? Let’s delve into the fascinating world of fasteners to uncover these crucial distinctions and their importance.

Why are strength grades and markings important for fasteners? Strength grades indicate the mechanical properties of fasteners, such as tensile strength and yield strength, which are critical for ensuring the reliability and safety of assemblies. Markings, on the other hand, provide a quick reference to identify these properties and verify compliance with standards.

What do the different strength grades mean? Fastener strength grades are often denoted by numbers and letters, which vary depending on the standard (e.g., ISO, ASTM, SAE). For example, an ISO 8.8 grade bolt has a minimum tensile strength of 800 MPa and a yield strength of 640 MPa. Understanding these grades helps in selecting the right fastener for specific applications.

How are fastener markings interpreted? Markings typically include the manufacturer’s identification and the strength grade. For instance, a bolt marked “8.8” and “XYZ” indicates it has an ISO 8.8 strength grade and was manufactured by XYZ company. These markings ensure traceability and guarantee that the fastener meets the required specifications.

What is the significance of understanding these distinctions? Correctly interpreting strength grades and markings ensures that the selected fasteners are capable of withstanding the mechanical demands of their application, preventing potential failures and enhancing the longevity and safety of the assembly.

In summary, understanding the difference between fastener strength grades and markings is crucial for selecting the right fasteners and ensuring the reliability and safety of various applications. By paying attention to these details, engineers and technicians can make informed decisions that enhance the performance and durability of their projects.

Why does the shape of fastener heads play a significant role in the ease of installation? Let’s explore the fascinating reasons behind this phenomenon and its implications for various applications.

What are the different shapes of fastener heads? Fastener heads come in various shapes, including hexagonal, Phillips, slotted, Torx, and more. Each shape serves a specific purpose and offers unique advantages in terms of installation and functionality.

How does the shape of fastener heads affect installation difficulty? The shape of the fastener head determines the type of tool required for installation and the ease of access to the fastening point. For example, hexagonal heads provide greater torque transmission and are less prone to stripping, while Phillips heads allow for quick and easy installation with a screwdriver.

What are the implications for different applications? In applications where space is limited or access is restricted, fasteners with low-profile or specialized heads may be preferred. Conversely, in high-torque applications, fasteners with robust and easily accessible heads are desirable to ensure secure and efficient installation.

In summary, the shape of fastener heads significantly influences the ease of installation and overall performance in various applications. Understanding the advantages of different head shapes can help in selecting the most suitable fasteners for specific needs, ultimately enhancing efficiency and reliability.

What are the challenges faced by fasteners in different environments?

Fasteners are subjected to a wide range of environmental factors, including temperature fluctuations, humidity, corrosion, and chemical exposure. These factors can impact the performance and longevity of fasteners if not properly addressed.

How do testing and certification address these challenges?

Testing procedures, such as salt spray testing, thermal cycling tests, and corrosion resistance testing, evaluate the performance of fasteners under specific environmental conditions. Certification ensures that fasteners meet industry standards and regulatory requirements for reliability and safety.

Why is testing and certification important for customers?

By investing in tested and certified fasteners, customers can have confidence in the reliability and performance of the products they use. This helps prevent potential failures, costly downtime, and safety hazards in various applications.

In conclusion, testing and certification of fasteners in different environments are essential steps to ensure their reliability, safety, and performance. By undergoing rigorous testing and obtaining certifications, fasteners can meet the diverse demands of various industries and applications with confidence.

Why do fasteners often loosen and corrode in engineering projects? Let’s explore the reasons.

What causes fastener loosening? Vibrations, thermal expansion, and inadequate tightening torque are common causes of fastener loosening. Over time, these factors can lead to compromised integrity and functionality of connections.

How does corrosion affect fasteners? Corrosion, often caused by exposure to moisture and environmental contaminants, weakens fasteners and undermines their structural integrity, leading to potential failure and safety hazards.

What measures can be taken to prevent fastener loosening and corrosion? Firstly, using thread-locking adhesives or mechanical locking devices can prevent fasteners from loosening due to vibrations. Secondly, selecting corrosion-resistant materials and coatings can protect fasteners from environmental damage.

Additionally, applying lubricants and anti-corrosion compounds during installation can reduce friction and protect fasteners from corrosion. Regular inspection and maintenance procedures should also be implemented to detect and address any issues before they escalate.

By understanding the factors contributing to fastener loosening and corrosion and implementing preventive measures, engineering projects can maintain the integrity and reliability of connections, ensuring safety and longevity.

Why do flat washers deform easily during assembly, affecting fastening integrity? Let’s uncover the reasons behind this phenomenon and explore effective prevention methods.

What causes flat washers to deform? Flat washers are often subjected to high pressure and stress during assembly, leading to plastic deformation, especially when excessive torque is applied during tightening.

How does deformation affect fastening integrity? Deformed flat washers may lose their ability to evenly distribute the load and maintain proper tension, resulting in uneven clamping force and potential loosening of connections over time.

What measures can be taken to prevent deformation? Firstly, selecting high-quality flat washers made from durable materials can reduce the risk of deformation. Secondly, controlling the tightening torque to within the specified range can prevent excessive stress on the washers. Additionally, using lubricants or anti-seize compounds during assembly can reduce friction and minimize the risk of deformation.

By understanding the factors that contribute to flat washer deformation and implementing preventive measures, we can ensure the integrity and reliability of connections in various applications.

Remember, the next time you assemble components with flat washers, consider the importance of proper installation techniques and material selection to prevent deformation and ensure secure connections.

Why are special treatments necessary for fasteners in high-temperature environments? Let’s explore the intriguing reasons behind this requirement.

What challenges do fasteners face in high-temperature conditions? Excessive heat can lead to thermal expansion, oxidation, and loss of mechanical properties in fasteners, compromising their integrity and performance.

How can special treatments address these challenges? Heat-resistant coatings and materials, such as ceramic or heat-resistant alloys, can be applied to fasteners to enhance their temperature resistance and prevent oxidation.

What are the benefits of specialized treatments for fasteners? Enhanced heat resistance ensures the reliability and longevity of fasteners in high-temperature applications, reducing the risk of premature failure and costly downtime.

In summary, special treatments for fasteners in high-temperature environments are essential to maintain their performance and integrity. By investing in these treatments, companies can ensure the reliability of their products in challenging operating conditions.

Whether it’s securing components in aerospace applications or industrial machinery in high-temperature environments, properly treated fasteners play a crucial role in ensuring safety, reliability, and efficiency.

Why do aerospace engineers seek out ultralight materials for fasteners?

It’s not just about shedding ounces; it’s about maximizing efficiency and performance. In the weight-sensitive realm of aerospace, every gram saved translates into enhanced fuel efficiency and increased payload capacity. But how do these ultralight materials maintain strength and durability amidst the rigors of flight? Let’s delve into the fascinating realm where innovation meets necessity, exploring the critical role of ultralight fasteners in pushing the boundaries of aerospace engineering.

How are Ultralight Fasteners Engineered to Meet Aerospace Standards?

Designing ultralight fasteners for aerospace applications is no small feat. Engineers employ advanced materials like titanium alloys and composite materials, balancing weight reduction with structural integrity. But it’s not just about the materials; precision engineering and stringent quality control ensure that these fasteners meet the rigorous demands of aerospace standards. From aerodynamic shapes to specialized coatings, every aspect is meticulously crafted to withstand the extreme conditions of flight while minimizing weight. Join us on a journey into the realm of aerospace innovation, where every gram counts and every fastener plays a crucial role.

What are the Advantages of Ultralight Fasteners in Aerospace Applications?

The benefits of ultralight fasteners in aerospace applications are manifold. Beyond weight savings, these fasteners contribute to increased fuel efficiency, extended range, and enhanced maneuverability. Their high strength-to-weight ratio allows for the construction of lighter, yet robust structures, pushing the boundaries of aircraft design. Moreover, reduced weight translates into lower operational costs and environmental impact, aligning with the industry’s sustainability goals. In the dynamic world of aerospace, where innovation is paramount, ultralight fasteners are indispensable for soaring to new heights.

Why do Fasteners Have Different Head Designs?

Ever pondered over the myriad head designs of fasteners? It’s not merely a matter of aesthetics; each design serves a distinct purpose, profoundly impacting functionality. The diversity in head designs reflects the complex needs of various applications, from distributing loads effectively to facilitating tool engagement. But why the variation? Let’s delve deeper into the intriguing world of fastener head designs to uncover the secrets behind their diversity.

How do various head designs impact fastener functionality?

The head of a fastener is not just a mere appendage; it’s a crucial element that dictates its performance. Different head designs offer distinct advantages, from providing increased torque resistance to enabling flush installations. For instance, a hexagonal head offers superior grip and torque transmission, ideal for heavy-duty applications, while a countersunk head sits flush with the surface, ensuring a sleek finish. Understanding the nuances of head designs is paramount in selecting the right fastener for your specific needs.

What are the factors influencing the choice of head design for fasteners?

The selection of a fastener’s head design is influenced by a myriad of factors, ranging from the application’s structural requirements to aesthetic preferences. Factors such as load distribution, accessibility for tooling, and environmental considerations play pivotal roles in determining the most suitable head design. Additionally, industry standards and regulations often dictate specific head designs for certain applications, ensuring compliance and safety. By carefully considering these factors, one can optimize the performance and longevity of their fastening solutions.

Why should fasteners undergo waterproof treatment? Let’s explore the intriguing reasons behind this necessity.

What challenges do unprotected fasteners face? Exposure to moisture and water can lead to corrosion, weakening the structural integrity and compromising the functionality of fasteners.

How does waterproof treatment enhance fastener performance? It creates a protective barrier that shields fasteners from moisture, preventing rust and corrosion. Additionally, waterproof coatings can improve longevity and durability, especially in outdoor or marine environments.

What happens without waterproof treatment? Unprotected fasteners are susceptible to rust, corrosion, and ultimately, failure. This can lead to safety hazards, structural damage, and costly repairs or replacements.

So, why invest in waterproof treatment for fasteners? It’s a proactive measure to ensure longevity, reliability, and safety in various applications, from construction to marine industries.

Remember, the next time you secure something with a fastener, it’s not just about holding things together; it’s about ensuring they withstand the test of time and the elements.

Why do certain fasteners require special materials? Let’s embark on an exploration to uncover the fascinating reasons behind this necessity.

What distinguishes these materials from the rest? They boast unique characteristics meticulously tailored to address specific challenges, whether it’s extreme temperatures, corrosive environments, or high-pressure conditions.

How do these materials elevate the performance of fasteners? Titanium alloys offer remarkable strength-to-weight ratios, ensuring durability without adding excessive weight. Stainless steel, on the other hand, exhibits excellent corrosion resistance, making it ideal for harsh environments.

Why is it crucial to use these specialized fasteners? Without them, structures would weaken over time, machinery would fail prematurely, and safety would be compromised. Specialized materials ensure reliability, longevity, and safety in critical applications.

So, the next time you marvel at the performance of a fastener, remember, it’s not just about nuts and bolts; it’s about the innovative materials that keep everything together.

Why do fasteners demand our attention even after they’ve done their job? Let’s unravel the mystery!

What lurks beneath the surface might surprise you. Corrosion, fatigue, and loosening silently threaten the integrity of connections.

Regular inspections act as guardians, detecting these threats before they escalate. Tightening loose fasteners and replacing corroded ones can save you from catastrophic failures.

How do you ensure the longevity of your connections? It’s simple: diligence and care. Implementing a maintenance schedule and using quality fasteners go a long way in preserving structural integrity.

So, next time you overlook the humble fastener, remember, it’s the silent hero holding your world together!

Why do fasteners adhere to standardized sizes? Let’s unlock the mystery behind this crucial aspect.

What chaos would ensue without standardized sizes? Imagine a world where every bolt, nut, and screw marched to the beat of its own drum.

How do standardized sizes simplify our lives? They provide uniformity, compatibility, and ease of replacement, ensuring seamless assembly and repair.

Think about it: no more hunting for elusive, custom-sized fasteners or worrying about mismatched components. Standardization brings order to the fastener universe.

So, the next time you marvel at the simplicity of swapping out a bolt or nut, remember, it’s the result of years of standardization efforts ensuring harmony in the world of fasteners.

Why do some connections thrive while others falter? The secret lies in the art of selecting the perfect fastener for each material.

When fastening materials like wood, choose screws with coarse threads for a secure grip. Metal connections demand bolts or nuts to withstand heavy loads, but be wary of galvanic corrosion when combining different metals.

For delicate materials like plastics, opt for self-tapping screws to prevent cracking. And in the realm of composite materials, adhesive fasteners offer seamless integration without compromising strength.

Understanding material properties and application environments is key. So, next time you embark on a fastening journey, remember, the right fastener is not just a tool; it’s the magic ingredient for a strong and lasting connection.

Why do some fasteners resist corrosion like superheroes while others succumb like mere mortals? Let’s delve into the fascinating world of metallurgy!

It’s all about the materials. Stainless steel fasteners, like guardians of the galaxy, possess a protective shield of chromium oxide that repels corrosion forces. Aluminum fasteners, with their sacrificial nature, willingly corrode to shield their companions. Titanium fasteners, the elite warriors, showcase unparalleled resistance due to their noble composition.

But it’s not just about their innate abilities; surface treatments and environmental factors also play crucial roles. Like alchemists, we manipulate coatings and platings to enhance their resistance. So, next time you wonder why some fasteners outlast the rest, remember, it’s a tale of metallurgical magic and strategic defense.

Have you ever tightened a bolt or a screw, only to find it loosening up over time? As a seasoned professional in the fastener industry, let’s delve into the intriguing world of mechanical relaxation and discover why some fasteners just can’t seem to hold on tight.

Why?

Fasteners, like all mechanical components, experience stress and strain during their lifespan. Over time, this stress can cause them to yield slightly, leading to a phenomenon known as “creep.” It’s like a gentle, imperceptible relaxation that occurs as the fastener settles into its role within the assembly.

How to Prevent the Drift?

But fear not! While some relaxation is inevitable, there are ways to keep your fasteners snug and secure for longer. Choosing high-quality materials, proper torque specifications, and regular maintenance can all help mitigate the effects of mechanical relaxation, ensuring that your constructions remain steadfast and reliable.

So, the next time you encounter a loose fastener, remember – it’s not just about tightening bolts; it’s about understanding the intricate dance of mechanical forces that govern their behavior. Join us in the quest for tighter, more resilient assemblies!

In the fascinating world of fasteners, have you ever stopped to wonder why some bolts and screws seem to sing a squeaky tune? As a seasoned professional in the industry, let’s embark on a journey to demystify this unique phenomenon.

Why?

Fasteners, those unsung heroes of construction, occasionally become the maestros of mechanical melodies. The culprit behind their squeaks is none other than friction – the age-old nemesis of silent assemblies. When metal meets metal under pressure, it’s like a dance where every move creates vibrations that echo as a distinct sound.

How to Silence the Symphony?

Now, you might be wondering, “How do we hush this unexpected musical performance?” Fear not! The key lies in the art of lubrication. By introducing the right lubricants between fastener surfaces, we can create a harmony that drowns out the squeaky notes. It’s the secret sauce to keeping your constructions blissfully quiet.

So, next time you hear your fasteners singing, remember – a touch of lubrication can turn their symphony into a silent masterpiece. Join us in the quest for a quieter, more harmonious world of fasteners!

In the intricate world of fasteners, the thread design stands as a silent orchestrator, shaping the very essence of connections in engineering. With a decade of hands-on experience in the fastener industry, let’s delve into the profound influence that thread design wields over the performance and reliability of fastener connections.

1. The Art of Engagement: Precision in Thread Design

Thread design is more than a winding pattern; it’s an art that governs the engagement between fastener components. Explore the nuances of pitch, depth, and profile, and how precision in thread design ensures optimal load distribution, enhancing the integrity of connections.

2. Strength in Form: Understanding Thread Profiles

Thread profiles, whether triangular, square, or trapezoidal, directly impact the load-bearing capacity of fasteners. Uncover the strengths and weaknesses of various profiles, and how selecting the right one aligns with the specific demands of each application.

3. The Tighter, the Better? Torque and Thread Relationship

Torque application is a delicate dance dictated by thread design. Delve into the correlation between thread geometry and torque requirements, deciphering how an ideal thread design contributes to achieving and maintaining the desired clamping force.

4. Stress and Strain: The Role of Thread Pitch

Thread pitch, often underestimated, plays a pivotal role in managing stress and strain. Explore how varying thread pitches affect the mechanical properties of fasteners, influencing their ability to withstand dynamic loads and vibrations.

5. Beyond Aesthetics: Aesthetic Thread vs. Performance Thread

While aesthetics matter, the aesthetics of thread design are secondary to performance. Unmask the dichotomy between visually appealing threads and those optimized for functionality, ensuring that your fasteners not only look good but perform impeccably.

6. Coordinated Symphony: Thread and Material Compatibility

Thread design must harmonize with the material properties for a seamless connection. Discover how different materials necessitate tailored thread designs, enhancing corrosion resistance, fatigue life, and overall durability.

7. Innovations in Thread Technology: Looking Toward the Future

As technology evolves, so does thread design. Explore emerging innovations in thread technology, from self-locking mechanisms to smart threads, paving the way for enhanced functionality and efficiency in fastener applications.

In conclusion, the impact of thread design on fastener connections is profound and multifaceted. By understanding the intricacies of thread design, engineers and professionals can make informed choices, ensuring that every connection is not just secure but optimized for superior performance. Let’s thread the path of excellence together! 🔩✨

#ThreadDesign #FastenerConnections #EngineeringPrecision

In the ever-evolving landscape of engineering, where extremes are constants, understanding the nuances of fastener performance becomes imperative. Drawing upon a decade of expertise in the fastener industry, let’s explore the intricacies of how fasteners respond to the challenges posed by high and low-temperature environments.

🌡️ The Thermal Tapestry: Impact of Temperature Extremes on Fasteners

Temperature fluctuations, whether soaring or plummeting, create a unique set of challenges for fasteners. How does the performance of these crucial components differ when exposed to the relentless heat of high-temperature environments or the bone-chilling cold of low-temperature surroundings?

🔥 Thriving in the Heat: High-Temperature Performance Considerations

In scenarios where temperatures reach scorching highs, the structural integrity of fasteners is put to the test. Explore with us the specialized alloys and heat-resistant coatings that empower our fasteners to withstand thermal expansion, maintain tensile strength, and resist oxidation, ensuring durability even in the hottest conditions.

❄️ Resilience in the Cold: Navigating Low-Temperature Challenges

As temperatures plummet, fasteners face challenges such as increased brittleness and reduced ductility. Dive into the realm of low-temperature engineering, where our fasteners are crafted with precision using materials engineered to resist embrittlement, ensuring optimal performance in freezing conditions.

🔬 Precision Engineering for Temperature Variability

Behind the scenes, precision engineering takes center stage. Our fasteners undergo rigorous testing and adhere to stringent quality control measures to guarantee performance consistency across a spectrum of temperatures. From cryogenic applications to high-temperature processing, our fasteners stand as a testament to reliability under thermal duress.

🌐 Adapting to Global Climates: Tailored Solutions for Every Environment

Whether your project spans arctic cold or scorching heat, our diverse range of fasteners offers tailored solutions. Explore the adaptability of our products, ensuring that your connections remain steadfast and reliable regardless of the temperature extremities in which they operate.

🛠️ Your Partner in Thermal Mastery: Elevate Your Engineering Standards

Choose a partner with a decade of proven excellence to navigate the complexities of fastener performance in high and low-temperature environments. Together, let’s elevate your engineering standards and conquer the challenges of temperature extremes.

Empower your projects with fasteners that thrive in the face of thermal challenges! 🔩✨

#FastenerPerformance #EngineeringChallenges #TemperatureResilience

Root cause: (1) The gap between the mold cutting edges is too large or too small and uneven. (2) The punch mold’s cutting edges become dull.(3) The displacement of the punch and die occurs due to prolonged production, causing misalignment and resulting in burrs on one side.

Solutions: (1) Ensure the processing accuracy and assembly quality of the punch and die, ensuring the correct gap and firm installation during assembly, and keeping the mold end face parallel to the press’s working surface. (2) The precision of the mold cutting surfaces should be high, and the press should have sufficient punching force. (3)Punching needle  will be replaced every 1200 times. (4) Preparing two inspection tools, one for operator ,the other for inspector, ensure the unqualified product can not been output.

The transverse and longitudinal toughness of steel plates are typically different. This is due to the grain structure formed during the manufacturing process of the steel plates.

During the manufacturing of steel plates, grains are formed through the processing and cooling of the material. In the transverse direction, the grains usually extend along the width of the plate. In the longitudinal direction, the grains extend along the length of the plate. This arrangement of grains determines the performance differences of the steel plate in different directions. Generally, the transverse toughness of the steel plate is relatively higher, while the longitudinal toughness is relatively lower. Transverse toughness mainly refers to the tensile strength and ductility of the steel plate in the transverse direction, meaning it has high tensile strength and good ductility, allowing for some plastic deformation under stress. On the other hand, longitudinal toughness refers to the tensile strength and ductility of the steel plate in the longitudinal direction. This difference in transverse and longitudinal toughness needs to be considered in applications. For example, in certain applications, it is necessary to consider the tensile strength of the steel plate in the longitudinal direction to ensure structural stability. In other cases, the tensile strength and ductility in the transverse direction may be more important, such as in situations that require stamping or bending processes. In conclusion, the transverse and longitudinal toughness of steel plates are typically different due to the arrangement of grains during the manufacturing process. This performance difference needs to be considered and addressed in different applications.

2.Solution:

During bending processes, change the bending direction from parallel to the direction of the metal material fibers to perpendicular to the direction of the metal material fibers. It has been verified that this solution can effectively eliminate the occurrence of cracks.

If you spent time in the fastener industry, you’re aware of the complex technology and engineering behind seemingly basic nuts, bolts, screws, and washers. Mechanical fasteners have been around for centuries, but that does not mean they’re fail-proof.

Fortunately, that’s where training comes in. The experts in the field guide us to better products, installation techniques, and overall application success. 

One such expert was the late Joe Greenslade, an icon in the fastener industry. He taught mechanical fastener technology for 45 years, publishing more than 300 informational articles. He also served eight years as the director of Engineering & Technology at the Industrial Fasteners Institute, a trade organization for North American mechanical fastener manufacturers.

In 2015, Greenslade compiled a list of his most frequently asked fastener questions with answers — including a section dedicated to fastener failure analysis. As he once pointed out, determining the reason for the failure is critical: “It is worthless to propose failure remedies before a definitive ‘root cause’ of the failure is determined. A root cause needs to be discovered before an effective remedy can be proposed.”

Here are a few of the questions he received with his answers to common fastener failures…

When a customer reports a fastener failure, what information should be gathered before trying to remedy the problem?
When a customer reports fastener failures, the information that should be gathered immediately before starting to try to remedy the problem includes:

• The exact part number
• The exact lot number
• The precise description of the failure and/or pictures of the failed parts
• Where the parts are used
• How the parts are driven and how tightening is controlled
• A sample of the broken and unused parts for analysis

When a customer complains about bolts and/or nuts vibrating loose, what is the likely cause?
The most likely cause of bolts and/or nuts vibrating loose is insufficient tightening. The most effective remedy is to use correctly calculated higher tightening torque or better determine the correct tightening value experimentally using extra components.

When a bolt failure has a “necked down” area in the threads, what is the most likely cause of the failure…and the most likely remedy?
When a bolt failure has a “necked down” area in the threads, the most likely cause of the failure is tensile overload due to over-tightening, or the bolt has insufficient strength for the load requirements of the design. The most likely remedy is to reduce torque if the failure occurs during installation or increase bolt strength if failure is during product use. Check the tightening calculation and/or do a tightening experiment.

When the fracture surface of a failed bolt exhibits a “shoreline” pattern, what is the most likely cause?
When the fracture surface of a failed bolt exhibits a “shoreline” pattern, the most likely cause of the failure is fatigue. The most likely remedy is to increase the tightening value.

When a bolt or screw has an intergranular fracture surface immediately under the head or at the first unengaged thread of the bolt or screw, what is the reason?
When a bolt or screw has an intergranular fracture surface within 48 hours of installation, the most likely cause is hydrogen embrittlement (see FTI note below). This can be remedied by baking the parts at 400° F for 14 or more hours. Or better yet, change to a finish not subject to hydrogen embrittlement. 

What if this same failure occurs weeks or months after installation?
When a bolt or screw has an intergranular fracture surface immediately under the head or at the first unengaged thread of the bolt or screw weeks or months after installation, the most likely cause is stress corrosion — also called environmental hydrogen embrittlement failures. 

This can be remedied by using fasteners with a core hardness of less than HRC 39. Otherwise, consider paint, coating, or a method that protects fasteners from the moist environment. For example, redesign the joint to prevent fasteners from being in moisture or avoid the use of dissimilar materials in the joint construction.

  FTI note… Hydrogen embrittlement (HE), is a permanent loss of ductility in a metal or alloy caused by hydrogen in        combination with stress — either applied externally or from internal residual stress. Generally, HE is classified under two broad categories based on the source of hydrogen: internal hydrogen embrittlement (IHE) and environmental hydrogen embrittlement (EHE), according to the “Fundamentals of Hydrogen Embrittlement in Steel Fasteners,” by Salim Brahimi.

What is the critical hardness above which hydrogen-induced failures can occur?
HRC 39 is the critical hardness above which hydrogen-induced failures can occur.

Why should designers avoid applications where dissimilar materials come in contact with one another? And what are the two approaches that can be taken to avoid failures when dissimilar materials must be mated with one another?
Designers should avoid applications where dissimilar materials come in contact with one another to avoid potential galvanic corrosion.

The two approaches that can be taken to avoid failures when dissimilar materials must be mated with one another is to select fastener materials that are closer to the component materials on the “galvanic scale,” and/or coat/paint the joint to keep moisture away from the joint.

  FTI note… Galvanic corrosion refers to corrosion damage induced when two (or more) dissimilar materials are brought into electrical contact under water.

(Article originated from Fastener Training Institute)

The late Joe Greenslade, an icon in the fastener industry, once wrote: “The technology of mechanical fasteners is much more complex and varied than most people understand until they embark on a career where they either supply or specify the use of mechanical fasteners.”

Those with a career in the industry can most certainly attest to the accuracy of this statement. Those who are in the process of training or upgrading their skills can also likely relate to the importance of learning about the different fastener types, materials, tools, and assembly methods available.

After all, these components are responsible for holding or joining applications together. It’s extremely important to specify and choose fasteners wisely and install them correctly.

Greenslade taught mechanical fastener technology for 45 years, publishing more than 300 informational articles. He also served eight years as the director of Engineering & Technology at the Industrial Fasteners Institute, a trade organization for North American mechanical fastener manufacturers.

In 2015, Greenslade compiled a list of his most frequently asked questions with answers that cover the specifying, inspecting, and installing of mechanical fasteners — and more.

Here are a few of his answers that are mostly related to structural bolts, materials, and related standards.

What are the four most commonly used structural bolt material standards and what material strength levels are they associated with?
The most commonly used structural bolt material standards are ASTM A325 and F1852, which are 120 ksi tensile strength, and A490 and F2280, which are 150 ksi tensile strength. These grades are covered in the ASTM F3125.

What is the difference between Type 1 and Type 3 structural bolts?
Type 1 structural fasteners are made from carbon or carbon-alloy steels and require coating and/or painting to avoid rusting. Type 3 structural fasteners are made from “weathering steel” that oxidizes to a point and stops, eliminating the need to coat or paint to avoid further rusting.

What is the dimensional standard covering inch structural bolts?
ASME B18.2.6 is the dimensional standard that covers inch structural bolts.

What are the two styles of structural bolts, and which is the most popular?
The two styles of structural bolts are Heavy Hex and Tension Control (TC). TC is the most popular structural bolt because of faster assembly and visual inspection.

What is the applicable washer standard for structural bolting?
ASTM F436 is the applicable washer standard for structural bolting.

What should be the relationship of an assembled bolt end be to the top surface of a nut in structural bolting?
An assembled bolt end should be at least flush to the top surface of a nut in structural bolting.

The rotational capacity (ROCAP) test: how is it performed and what is its primary purpose?
A “ROCAP” test is performed using exact bolts, nuts, and washers tightened in a Skidmore (hydraulic) tester, tightening the nut to 10% of the target bolt tension. Then, rotate the nut the number of degrees designated in the ASTM F3125 standard. The bolts must not break and once the nut is broken loose, the nut must unscrew by hand.

The primary purpose of a ROCAP test is to determine if adequate nut lubrication is present to enable proper fastener tightening without failure. According to ASTM F3125 (Table 3, Note A), the ROCAP testing of galvanized assemblies is mandatory. Testing may be required by the purchaser by specifying “Supplementary Requirement S.4” at the time of inquiry and order for plain or assemblies having other coatings.

The test must be conducted using the exact lots of bolts, nuts, and washers, if any, that will be used on a job site.

Why should all of the exact fastening components be shipped to the job site by the same supplier?
According to the RCSC standard, when performing a ROCAP test, all of the fastening components should be shipped to the job site by the same supplier to assure the exact mating parts will work on the job site.

What is a pre-installation test and why is it required?
A “pre-installation test” is a test performed on a job site using the exact components and assembly technique specified for the structure.

The pre-installation test is required to demonstrate that the bolts, nuts, and washers on the job site will assemble properly when constructing the structure prior to actual assembly starting. It must be performed and documented by the assembly crew doing the installation.

What is the specification that governs structural steel assembly?
Research Council on Structural Connections (RCSC) is the specification that governs structural steel assembly

What are the three things that can be tried to stop the galling of stainless bolt and nut threads?
Three things that can be tried to stop the galling of stainless bolts and nuts are using a different grade of stainless for the mating components, slow down the installation RPMs, and lubricate the bolt and/or nut with thread lubricant.

(Article originated from Fastener Training Institute)