Analysis and Avoidance Guide for Common Misconceptions in Fastener Selection
Fasteners, though small in size, play a crucial role in various industrial fields such as machinery manufacturing, construction engineering, and electronic device assembly. They serve as essential components for connecting and fixing parts, ensuring the stable operation of equipment and the safety and reliability of structures. However, in the actual process of fastener selection, due to insufficient understanding of technical specifications, improper cost considerations, and the influence of empiricism, there are often some misunderstandings. These misunderstandings can, at best, lead to a decline in equipment performance and an increase in maintenance costs, and at worst, trigger safety accidents, causing immeasurable losses. This article will deeply analyze the common misunderstandings in the fastener selection process and provide scientific and reasonable solutions to help practitioners improve the accuracy and reliability of fastener selection.
I. Neglecting the Requirements of the Usage Environment and Working Conditions
(1) Inadequate Understanding of Environmental Factors
When selecting fasteners, many people often only focus on the basic specifications and prices of the products, while ignoring the impact of the usage environment on the performance of fasteners. For example, in a humid, high-salt fog marine environment or a chemical corrosion environment, if ordinary carbon steel fasteners are selected, due to their poor corrosion resistance, they will quickly rust, resulting in a decrease in connection strength and even structural failure. In high-temperature environments, ordinary metal fasteners may experience problems such as thermal expansion and creep, reducing the fastening effect; in low-temperature environments, some materials become brittle and are prone to fracture.
(2) Incomplete Consideration of Working Conditions
In addition to environmental factors, working conditions are equally important. For parts subjected to vibration and impact loads, if the selected fasteners have poor anti-loosening performance, they may loosen under long-term vibration, causing equipment failures. In high-speed rotating equipment, if the dynamic balance performance of the fasteners does not meet the standards, it will exacerbate equipment vibration and affect the service life and operating accuracy of the equipment. Moreover, for occasions with fatigue load requirements, if fasteners with good fatigue performance are not selected, fatigue fractures may occur in a relatively short period.
II. One-sided Pursuit of Low Cost
(1) Quality Risks of Low-priced Products
Cost is an important consideration in the procurement of fasteners. However, some purchasers overly pursue low prices and choose products that do not meet quality standards. Low-priced fasteners often cut corners in materials, manufacturing processes, surface treatments, etc. For example, inferior steel is used, and its chemical composition and mechanical properties cannot meet the standard requirements; simple and rough manufacturing processes are adopted, resulting in poor thread accuracy and large dimensional deviations; the surface treatment process is not standardized, with insufficient thickness and poor adhesion of the protective layer, unable to effectively protect the fasteners. These quality problems make the fasteners more likely to be damaged during use, increasing equipment maintenance and replacement costs. In the long run, it actually causes greater economic losses.
(2) Ignoring the Life Cycle Cost
The one-sided pursuit of low cost is also reflected in only focusing on the procurement cost of fasteners while ignoring their life cycle cost. The life cycle cost includes procurement cost, installation cost, maintenance cost, and replacement cost, etc. Although high-quality and reliable fasteners have a higher procurement price, due to their stable performance and long service life, they can reduce installation and debugging time, lower maintenance frequency and replacement times, thereby reducing the overall cost. On the contrary, low-priced and inferior fasteners may require frequent maintenance and replacement, not only increasing labor costs and downtime costs but also possibly affecting production progress due to equipment failures, bringing greater indirect losses.
III. Selection Based Solely on Experience without Scientific Basis
(1) Limitations of Empiricism
When selecting fasteners, some practitioners overly rely on past experience, believing that if a certain type of fastener worked well in the past, it can be directly applied in new projects. However, different projects may vary in design requirements, usage conditions, manufacturing processes, etc. Fasteners that were suitable in the past may not be appropriate in new situations. For example, with the continuous development of new materials and processes, the structural and performance requirements of equipment are also constantly increasing. If fasteners are still selected according to traditional experience, it may be unable to meet the high-precision and high-reliability requirements of new equipment.
(2) Failure to Refer to Standard Specifications and Technical Documents
National standards and industry specifications provide scientific guidance and basis for fastener selection. However, some people do not fully refer to these materials during the selection process. For example, they do not understand the strength grade standards of fasteners and randomly choose low-strength grade fasteners to replace high-strength grade ones, resulting in the connection parts being unable to withstand the designed load; they are not familiar with thread specifications, tolerance fits, and other standards, causing improper matching between fasteners and connected components, affecting the connection effect. In addition, ignoring information about usage conditions and installation requirements in product technical documents is also likely to lead to selection errors.
IV. Misinterpretation of Fastener Performance Parameters
(1) Ambiguous Understanding of Strength Grades
The strength grade of fasteners is an important indicator to measure their load-bearing capacity. However, many people do not clearly understand the concept and meaning of strength grades. For example, they confuse the tensile strength and yield strength of bolts and mistakenly believe that bolts with high tensile strength can meet the requirements of all working conditions. In fact, in some occasions where preventing plastic deformation is required, the yield strength is more crucial. Moreover, the representation methods and meanings of strength grades under different standard systems may vary. If not distinguished, it is also easy to lead to selection errors.
(2) Neglecting Other Performance Parameters
In addition to strength grades, fasteners have many other important performance parameters, such as hardness, toughness, corrosion resistance, anti-loosening performance, etc. In actual selection, these parameters are often ignored. For example, in occasions requiring wear resistance, the hardness requirements of fasteners are not considered; in parts subjected to impact loads, the toughness of fasteners is not paid attention to; in structures with anti-loosening requirements, appropriate anti-loosening fasteners are not selected, or effective anti-loosening measures are not taken, thus affecting the normal operation and safety of the equipment.
V. Unreasonable Selection and Matching
(1) Mismatch between Fasteners and Connected Components
The selection of fasteners must match the materials, structures, and dimensions of the connected components. If the selected fasteners are too large or too small, it will cause difficulties in installation and fail to achieve the ideal fastening effect; if the materials of the fasteners do not match those of the connected components, electrochemical corrosion may occur. For example, using carbon steel fasteners on aluminum alloy connected components, due to the different electrode potentials of the two materials, electrochemical corrosion is likely to occur in a humid environment, accelerating the damage of the fasteners and connected components.
(2) Incompatibility among Fastener Components
For some fastener systems composed of multiple parts, such as bolt connection sets (bolts, nuts, washers, etc.), the components must be matched with each other. If parts from different manufacturers or batches are randomly combined, problems such as inconsistent dimensional tolerances and mechanical properties may occur. For example, if the thread accuracy of the nut does not match that of the bolt, it will lead to unstable tightening torque and affect the connection strength; if the hardness and size of the washer are inappropriate, it cannot effectively distribute the pressure, possibly causing damage to the surface of the connected component.
VI. Solutions to Avoid Misconceptions in Fastener Selection
(1) Comprehensive Assessment of the Usage Environment and Working Conditions
Before selecting fasteners, a comprehensive and detailed assessment of the usage environment and working conditions must be carried out. Thoroughly understand factors such as the temperature, humidity, pH value, and salt fog concentration of the environment, as well as the load types (static load, dynamic load, fatigue load, etc.), load magnitude, vibration frequency, rotational speed, and other working conditions during equipment operation. Based on the assessment results, select fastener materials and types with corresponding performance. For example, in a marine environment, give priority to selecting corrosion-resistant materials such as stainless steel and hot-dip galvanized fasteners; in high-temperature environments, choose high-temperature alloy material fasteners; for parts subjected to vibration loads, use fasteners with good anti-loosening performance, such as nylon lock nuts and spring washers.
(2) Comprehensive Consideration of Cost Factors
Abandon the concept of one-sidedly pursuing low cost and adopt the life cycle cost analysis method to evaluate the economy of fasteners. When purchasing, not only compare the product prices of different suppliers but also pay attention to factors such as product quality, performance, and after-sales service. Select high-quality and cost-effective fasteners. Although the initial procurement cost may be higher, in the long run, it can reduce equipment maintenance costs and downtime losses and improve production efficiency. In addition, by optimizing the design and reasonably selecting the specifications and quantities of fasteners, costs can also be reduced while ensuring performance.
(3) Scientific Selection Based on Standard Specifications and Technical Documents
Strictly follow national standards, industry specifications, and product technical documents for fastener selection. Be familiar with the standards and technical requirements of various fasteners and master the application ranges of different strength grades, specifications, dimensions, and performance parameters. In the design stage, refer to relevant design manuals and technical materials, and reasonably determine the types, specifications, and quantities of fasteners according to specific usage requirements. For complex or special working conditions, you can also consult professional fastener manufacturers or technicians to obtain more accurate selection suggestions.
(4) Accurate Understanding and Grasp of Performance Parameters
Deeply study and understand various performance parameters of fasteners and clarify the importance of different performance parameters under different working conditions. During the selection process, comprehensively consider parameters such as strength grade, hardness, toughness, corrosion resistance, and anti-loosening performance according to actual needs. For example, for bolt connections subjected to large tensile forces, give priority to selecting bolts whose tensile strength and yield strength meet the requirements; for fasteners that need to work in harsh environments, focus on their corrosion resistance; for occasions with anti-loosening requirements, select appropriate anti-loosening methods and anti-loosening fasteners.
(5) Ensure Reasonable Selection and Matching
During the selection process, fully consider the matching between fasteners and connected components as well as among fastener components. According to the materials, structures, and dimensions of the connected components, select fasteners of appropriate specifications and types to ensure a good connection and fastening between the fasteners and the connected components. For fastener components, try to select products from the same manufacturer and batch to ensure that the dimensional tolerances and mechanical properties of each part match. Before installation, carefully check the quality and dimensions of the fasteners to ensure a smooth installation process and achieve the ideal fastening effect.
Fastener selection is a seemingly simple but crucial task. Any small misunderstanding may lead to serious consequences. Only by fully recognizing the common selection misunderstandings, adopting scientific and reasonable solutions, and comprehensively and accurately selecting fasteners can we ensure the safe and reliable operation of equipment and structures, reduce costs, and improve production efficiency. In practical work, practitioners should continuously learn and accumulate experience, pay attention to industry trends and the development of new technologies, and continuously improve their professional level in fastener selection.
