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July 24th, 2026

Proper Maintenance Methods for Stainless Steel Screws and Tips for Extending Their Service Life: “It is stainless steel, so it should not rust”—in manufacturing sites, this misconception ceaselessly invites unexpected troubles and increased costs. Certainly, Stainless Steel possesses excellent corrosion resistance, but in high-temperature, high-humidity environments like Vietnam, or under improper maintenance, corrosion and “galling” occur, directly linking to serious risks such as production line stoppages and product recalls. Particularly in the Vietnam market, where precision equipment and automotive parts manufacturing are accumulated, the reliability of fastening parts is a lifeline that determines the brand value of the final product. In this article, based on the specialized knowledge of fastening parts that Ohta Vietnam has cultivated over many years, we will scientifically reaffirm the characteristics of stainless steel screws and explain correct maintenance methods and secrets for extending service life that can be immediately practiced on-site. We present a concrete roadmap to realize significant reductions in procurement costs and downtime by reducing part replacement frequency through appropriate management. This series of knowledge should become a beneficial asset for all manufacturing industry stakeholders, from management layers to on-site technical personnel. First, let us share the technical basics. The reason stainless steel is hard to rust is that the contained chromium (Cr) bonds with oxygen to form a dense protective film called a “Passive Film” on the surface. The thickness of this film is merely 1 to 3 nanometers (1 nanometer is one-millionth of a millimeter), which is extremely thin, but it possesses a self-repairing function. However, this self-repairing function is not all-powerful. Even with SUS304 (18Cr-8Ni) defined by standards such as JIS G 4303, if iron powder adheres to the surface (“contact rust”) or in the presence of chloride ions (seawater or salty breeze), the film is destroyed, regeneration cannot keep up, and corrosion progresses. In particular, chlorine ions locally destroy the passive film and become the main cause of deep hole-like rust called Pitting Corrosion. Vietnam’s average humidity exceeds approximately 80% throughout the year, and can reach nearly 90% during the rainy season. This high humidity makes it easy for a moisture film to form on metal surfaces, promoting electrochemical corrosion reactions. Furthermore, accompanying rapid industrialization, the atmosphere in factory zones may contain sulfur oxides (SOx) and nitrogen oxides (NOx); these react with moisture to create an acidic environment, becoming factors that accelerate the corrosion of stainless steel screws. Even stainless steel screws that can be expected to have a durability of over 30 ...

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July 17th, 2026

5 ways to prevent screws from loosening that you should know at the manufacturing site: In the manufacturing industry, the risk of a single “screw loosening” causing a serious accident or recall is one of the issues that top management and site managers should be most vigilant about. In fact, according to a cause investigation of screw fastening-related troubles (1977 domestic survey in Japan), tightening defects account for about 43% and loosening accounts for about 20%, and it is considered highly probable that these can be prevented with appropriate knowledge and management. Especially in overseas production bases like Vietnam, environmental factors different from Japan (temperature, humidity, vibration) and quality variations in procured parts amplify the risk of loosening. Overconfidence that “it’s fine because I tightened it with the usual torque” can lead to unexpected line stoppages and increased costs. In this article, for technical staff and procurement managers at manufacturing sites, we will explain “5 loosening countermeasures” that can be implemented immediately, while scientifically unraveling the mechanism of screw loosening. Furthermore, we will touch upon stable procurement in Vietnam and the latest axial force management utilizing IoT, presenting concrete action plans to protect factory safety and productivity. Screw loosening is broadly classified into “loosening accompanied by rotation” and “loosening not accompanied by rotation.” What is frequently overlooked on site is “initial loosening (initial settling),” which is not accompanied by rotation. Immediately after tightening a screw, minute irregularities on the bearing surface of the bolt, the screw threads, and the contact surface of the clamped material are crushed and smoothed by the external load. As a result, the contact surface sinks at a micro level (plastic deformation), and the bolt tension (axial force) decreases. Generally, it is said that the axial force immediately after tightening decreases by several percent to about 10% within a few hours to a few days, and design and retightening considering this are necessary. More serious is “return rotation” caused by vibration or impact. When the frictional force acting between the bolt and nut is momentarily lost due to lateral cyclic loading (such as Junker vibration), the screw begins to rotate in the loosening direction naturally along its own lead angle. Once rotation begins, the axial force rapidly approaches zero, leading to falling off or breakage in the worst case. From here, we will introduce 5 specific countermeasures to consider at manufacturing sites from the viewpoints of cost, workability, and reliability. The basic and ultimate secret of loosening countermeasures is to apply ...

Column
July 10th, 2026

What is a stud bolt? ｜Easy explanation in 3 minutes: In manufacturing sites and plant designs, “Stud Bolts” are indispensable as unsung heroes. Unlike general hexagon bolts, this bolt has the unique shape of “having no head.” Why is it frequently used in flange connections for automotive engines and chemical plants? In conclusion, the biggest reasons for adopting stud bolts are “protection of the base material’s threads” and “ease of repeated disassembly and assembly”. They demonstrate their true value especially in locations requiring frequent maintenance or when fastening with base materials of relatively lower strength, such as aluminum die-cast. In this article, we will explain important points that procurement and technical personnel should know in 3 minutes, ranging from basic knowledge of stud bolts and how to read strength classes based on JIS standards, to procurement strategies in Vietnam which is a key card for cost reduction. We will also present hints to solve your company’s procurement challenges while incorporating the merits of local procurement provided by Ohta Vietnam. A Stud Bolt refers to a “rod-shaped bolt threaded at both ends and having no head”. Generally, it takes a structure where one side is embedded into the base material (engine block or equipment body) and a nut is attached to the other side for tightening. In JIS standards (Japanese Industrial Standards), it is classified as a “stud,” and broadly divided into the following types based on shape. Double end (Type with an implant side and a nut side): It is divided into the side screwed into the base material (implant side) and the side where the nut is tightened (nut side). Full thread (All-thread type): A type where the entire shaft is threaded, mainly used for flange connections, etc. Due to this shape, stud bolts also serve as “positioning guides.” When installing heavy flanges or covers, by planting the stud bolts first, parts can be temporarily placed by passing them through the bolts, significantly improving work efficiency. When compared to hexagon bolts, stud bolts have clear engineering merits. Reduced damage to base material: Repeating attachment and detachment with hexagon bolts wears down the female threads of the base material (especially aluminum or cast iron), and in the worst case, the threads get crushed. With stud bolts, since the base material side remains fixed and only the nut side is operated, expensive component bodies are not damaged. Securing strong axial force: Since it is tightened with nuts from both sides (or ...

Column
July 03rd, 2026

Easy explanation in 3 minutes “What is T-bolt?”: “T-bolts” are indispensable for fixing jigs and assembling aluminum frames at manufacturing and construction sites. As the name suggests, this bolt has a T-shaped head. While it looks like a simple shape at first glance, it is an important fastening part that significantly impacts equipment availability, worker safety, and even procurement costs. For many engineers and purchasing managers, T-bolts are such a familiar presence that there are surprisingly few opportunities to deeply consider the details of their standards, optimal selection criteria, or possibilities for cost reduction. In this article, we will comprehensively explain everything from basic knowledge such as the fundamental definition and mechanism of T-bolts to proper use based on strength class and material, and even the latest procurement strategies utilizing Vietnam, incorporating the perspective of Ota Vietnam. We have condensed hints into content that can be read in just 3 minutes to improve daily operational efficiency and optimize procurement costs. As manufacturing professionals, let’s take the first step in “on-site improvement” by reviewing even a single fastening part from here. The T-bolt (T-Slot Bolt / Hammer Head Bolt) is a special bolt with a head shaped like the letter “T”. This unique shape is designed to be inserted into “T-grooves (T-slots)” provided on machine tool tables and aluminum structural materials (aluminum frames). Unlike general hex bolts, T-bolts can be inserted from any position in the groove and engaged (locked) with the groove wall by rotating them 90 degrees. This allows for firm fixation simply by tightening the nut. For example, when fixing a workpiece (object to be machined) on the bed of a machining center, the ability to flexibly adjust the position of clamp jigs is due to this functionality of the T-bolt. While T-bolts are used in a wide range of fields, they are broadly used for the following two purposes. For Machine Tool & Jig Fixation: They are used to fix vises and clamps using the T-slots on the tables of milling machines, drilling machines, presses, etc. Since high fastening force is required here, high-strength materials such as carbon steel (S45C, etc.) and chromium-molybdenum steel (SCM435) are preferred. For Aluminum Frame Assembly: They are used for assembling structures using aluminum extrusion materials, such as safety fences in factories, workbenches, conveyor lines, and even mounts for solar panels. Here, the advantage of the T-bolt being able to be inserted later (post-installation) is valued in production lines with ...

Column
June 26th, 2026

What is a U-bolt? ｜Easy explanation in 3 minutes: Do you often see “U-shaped bolts” in various places at manufacturing sites, such as fixing pipes in factories or the undercarriage of vehicles? That is the “U-Bolt” we will explain this time. Although it looks like a simple shape, it is actually one of the fasteners with the most ordering mistakes due to the difference between “nominal diameter” and “actual size.” Especially in manufacturing sites in Vietnam, selecting materials compatible with the high-temperature, high-humidity climate and procuring special sizes for sudden equipment maintenance tend to be challenges. In this article, from the perspective of a procurement professional that Ohta Vietnam has cultivated over many years, we will explain the basic knowledge of U-bolts, how to read standards, and selection points suitable for Vietnam’s unique environment in an easy-to-understand manner in 3 minutes. Let’s acquire the correct knowledge and prevent procurement mistakes and on-site troubles before they happen. As the name implies, a U-bolt is a bolt bent into the shape of the alphabet “U”, featuring threads cut on both ends. While a general hex bolt “tightens and joins two members,” a U-bolt is mainly used to “embrace and fix pipe-shaped objects to a mount or wall surface.” It plays an important role not only in physical support capacity but also in preventing pipe displacement or falling off due to vibration, and its uses are diverse. Pipe support: Fixing pipelines for water, air, gas, chemicals, etc., in factories (most common) Vehicle parts: Fixing leaf springs of trucks and trailers Building equipment: Installing ducts and antenna masts Ship rigging: Fixing pipes and cables inside ships When selecting a U-bolt, it is essential to understand the following four dimensional elements. Nominal Diameter (A Call/B Call): The size of the object (pipe) to be fixed. It is expressed as “50A” or “2B”. Thread Nominal (d): The thickness of the thread parts at both ends. M6, M8, M10, etc., are common. Inner Width (W): The width inside the U-shape. This must be slightly larger than the outer diameter of the pipe to fit. Leg Length (L): The length of the straight rising part, including the threaded part. The most common mistake in ordering U-bolts is confusing the pipe’s “Nominal Diameter (A)” with the “Actual Size (mm).” For example, when ordering a “U-bolt for 50A pipe,” the inner width of the U-bolt is not approximately 50mm. The “50A” for carbon steel pipes for ordinary piping in ...

Column
June 19th, 2026

The Key to Reducing Defects: Management Methods for Stabilizing Screw Fastening Quality: In modern manufacturing, screw fastening plays an absolutely fundamental role in ensuring product safety and reliability. It forms the backbone of products across various industries, from automotive, home appliances, and medical devices to aerospace, and is a critical factor influencing their function and performance. However, if a defect occurs in this screw fastening, the impact can be immense. When defective products occur, companies incur not only direct costs such as rework, scrap, and repairs, but also immeasurable losses in the form of product recalls, customer complaint handling, and damage to brand image. According to estimates by the Ministry of Economy, Trade and Industry (METI), the annual loss due to defective products in the manufacturing industry in Japan alone is said to reach several trillion yen (approximately 5 trillion yen annually). Furthermore, fastening components often account for an average of 5% to 15% of product costs, and their quality directly impacts the overall cost and reliability of the product. One study reported that approximately 15% of product recall causes are related to fastening defects, clearly demonstrating their importance. Against this backdrop, stabilizing screw fastening quality is an urgent challenge that goes beyond mere cost reduction, directly enhancing a company’s competitiveness. Ohta Vietnam provides high-precision fastening solutions to address the quality challenges faced by manufacturing sites in Vietnam, strongly supporting our customers in defect reduction and productivity improvement. Screw fastening defects directly lead to problems such as product malfunction, reduced safety, and shortened lifespan. For example, fastening defects in critical safety parts of automobiles can lead to serious accidents. In the case of medical devices, they could potentially cause life-threatening situations for patients. These issues can escalate into recalls and large-scale complaints, severely damaging a company’s credibility and resulting in enormous economic losses. Product accidents caused by fastening defects can amount to hundreds annually in specific industries (e.g., automotive parts). The main causes of screw fastening defects are diverse, but include the following: Insufficient or excessive tightening torque (the force used to turn a screw): Deviating from the specified torque can result in insufficient clamping force or damage to screws and components. Experimental data shows that if tightening torque deviates by ±20% from the specified value, fastening reliability can decrease by more than 50%. Insufficient axial force (the tensile force generated when a screw is tightened): Even if the tightening torque is appropriate, axial force can be insufficient due to variations in ...

Column
June 12th, 2026

Left-Hand Screw Applications and Selection: Enhancing Product Safety and Reliability by Differentiating Usage from Right-Hand Screws: In the manufacturing industry, the selection of fastening components is critically important for ensuring product safety, reliability, and efficiency. Specifically, left-hand screws (also known as reverse-thread or counter-clockwise screws), in contrast to common right-hand screws, play an indispensable role in specific applications due to their unique fastening principle. Incorrect screw selection can lead to significant risks such as reduced product performance, malfunctions, accidents, and even large-scale recalls. In fact, approximately 15% of product accidents are attributed to fastening failures, and despite fastening component costs accounting for only about 3% to 5% of total product costs, selection errors can shorten product lifespan by up to 20% and potentially increase maintenance costs by over 10%. This article provides a detailed explanation of the principles of left-hand screws, their primary applications, effective differentiation from right-hand screws, and crucial considerations for design and procurement. Furthermore, considering the current state of fastening component procurement in Vietnam’s rapidly developing manufacturing sector, we will introduce how Ohta Vietnam can contribute to solving our customers’ challenges. The rotation direction of a screw is a fundamental element of its fastening principle. The most common “right-hand screw” tightens when turned clockwise (to the right) and loosens when turned counter-clockwise (to the left). Its threads are formed with a right-hand helix, which can be likened to the “right-hand rule.” In contrast, a “left-hand screw” exhibits the opposite rotational characteristic: it tightens when turned counter-clockwise and loosens when turned clockwise. Its threads are formed with a left-hand helix, and often, an “LH” (Left Hand) marking is stamped on the screw head or shank to prevent incorrect assembly. Screw fastening is achieved by efficiently converting applied rotational torque into axial load (axial force). This conversion efficiency largely depends on the screw’s lead angle (the angle determined by the axial distance the thread advances in one revolution and the screw’s diameter). For general fastening applications, the lead angle is typically designed within the range of 2 to 5 degrees; if this angle is too small, fastening efficiency decreases, and if it’s too large, self-locking capability may be lost. In Japan, JIS B 0205 (Metric Coarse Threads) boasts a penetration rate of over 90% and is the most widely used standard. For instance, typical tightening torques for M6 metric coarse threads are around 10 N·m, and for M10, around 50 N·m, generating axial forces ranging from several kN to tens of kN. Left-hand screws follow ...

Column
June 05th, 2026

What is an anchor bolt? ｜Easy explanation in 3 minutes: “Anchor bolts” are indispensable for installing machine tools in factories and maintaining the structure of buildings. These parts, which firmly connect equipment and structures to concrete floors or foundations, are truly the “unsung heroes” of the manufacturing site. However, if appropriate selection or installation is not performed, there is a risk of serious accidents such as overturning during earthquakes or equipment detachment. In fact, data shows that a high percentage of construction defects related to structural hardware are found during inspections of new construction, making correct knowledge the cornerstone of safety management. In this article, we will explain everything from basic types of anchor bolts to the concept of strength calculation and installation points to note on-site, in content that can be read in 3 minutes for procurement and maintenance personnel in the manufacturing industry. Please use this for your company’s safety measures together with the procurement solutions provided by Ohta Vietnam. Anchor bolts are a general term for bolts that are embedded in a base material (mainly concrete) and use their tensile strength and shear strength to fix an object. Their fixing principles are mainly classified into the following three types. Friction fixation: A part of the anchor opens and fixes by the frictional force pressed against the hole wall (common in metal types). Adhesion fixation: Fixing the bolt and the hole wall together with the bonding force of resin (adhesive) (Chemical Anchor). Shape fixation: Embedded before concrete placement, fixed by the curved tip (L-shape/J-shape) hooking into the concrete (Foundation Bolt). Anchors handled at manufacturing sites are largely divided into “Cast-in-place anchors” and “Post-installed anchors”. This type is installed before pouring concrete. They are L-shaped or J-shaped, and have the highest structural strength and excellent reliability. They are used for foundations of large machinery and fixing pillars of buildings. At Ohta Vietnam, production and supply in custom sizes based on drawings are possible. This type is installed after drilling holes in existing concrete floors. They are frequently used for factory layout changes and fixing additional equipment. Metal Anchors (Mechanical Anchors) Feature: The tip opens by driving in or tightening the bolt, biting into the concrete to fix it. Merit: Installation is fast, and load can be applied immediately. Demerit: Because the expansion force puts stress on the concrete, it may cause cracks if used near edges. Usage: Fixing piping brackets, installing handrails, and other uses under medium load or ...

Column
May 22nd, 2026

What is a hexagon socket head bolt? Basic knowledge of standards, strength, and procurement in Vietnam: In manufacturing design, development sites, and procurement operations, the “Hexagon Socket Head Cap Screw” is one of the most frequently seen fastening parts. Also known as “Cap Bolts” or “Cap Screws,” these are not merely simple fasteners. Compared to conventional hex bolts, they allow for more space-saving designs and achieve extremely high tightening strength, making them indispensable in precision equipment fields such as machine tools, automotive parts, and automation lines. Especially in Vietnam’s manufacturing sites, stable procurement of bolts meeting quality standards similar to Japanese companies (JIS standards, etc.) directly impacts production line utilization rates and final product safety. This article briefly explains the basic definition, technical merits, strength class details, and efficient procurement methods in Vietnam for busy practitioners in 3 minutes. Together with the solutions provided by us, Ohta Vietnam, we hope this serves as an aid to your procurement strategy. Hexagon socket head cap screws are a general term for bolts with a hexagonal hole in a cylindrical head. In Japanese Industrial Standards (JIS), they are defined as “JIS B 1176” and conform to the international standard “ISO 4762”. The biggest feature is that they use a “Hexagon Key (Allen Key)” instead of a spanner or wrench for tightening. While general hex bolts (JIS B 1180) are turned by gripping the outside of the head, hexagon socket head cap screws transmit torque using the inside (hole) of the head. This eliminates the need to secure space around the bolt for turning tools, contributing significantly to the miniaturization and weight reduction of machinery. The greatest design advantage is the suitability for “counterboring” processing, where the head is embedded inside the part. The cylindrical head fits perfectly into the counterbored hole, keeping the part surface flat. This prevents the bolt head from protruding on moving machine parts, reducing labor accident risks such as workers’ clothing getting caught. It also makes the appearance smart, making it suitable for products requiring good design. Another major reason why hexagon socket head cap screws are chosen lies in their overwhelming “strength.” While many iron hex bolts generally in circulation are strength class “4.8”, standard hexagon socket head cap screws are manufactured with the extremely high strength class of “12.9”. This number “12.9” represents the following mechanical properties: 12: Indicates a tensile strength of 1,200 N/mm² (122 kgf/mm²). This means it can withstand a load of approximately 122 kg per square millimeter. 9: Indicates ...

Column
May 15th, 2026

What is a bolt? ｜Easy explanation in 3 minutes: In the manufacturing industry, the “bolt” is a critical component that, while basic, dictates product quality and safety. Approximately 2,000 to 3,000 bolts and nuts are used per automobile, and the failure of just one can lead to serious accidents. However, ambiguous instructions like “Bring me an M6 bolt” are common on the factory floor, often leading to overlooked differences in property classes or surface treatments. Particularly in Vietnam, which has become a key point in supply chains in recent years, stably procuring Japanese-quality fasteners at appropriate prices is an urgent issue for many companies. In this article, we will explain everything from the basic definition of bolts and how to read often-overlooked property classes to optimal procurement strategies in Vietnam, summarizing the points procurement and technical staff need to know in 3 minutes. Including the hybrid “Trading Company x Manufacturer” solution provided by Ohta Vietnam, we deliver information to update your procurement operations. Generally, “Bolts” are included within the broad classification of “Screws,” but a clear distinction exists in JIS standards (Japanese Industrial Standards) and practical field work. The biggest difference is “whether or not it is used in combination with a nut.” Items that are tightened solely into a female thread (tapped hole) cut into the target object are called “Machine Screws.” On the other hand, items that pass through the target object and are fixed by tightening with a nut from the opposite side are defined as “Bolts.” However, since hexagon bolts are sometimes screwed into tapped holes, it is also common to distinguish them by shape (those with large heads like hexagons that are turned with a spanner or wrench). Bolts are mainly composed of the following three elements. Head: The part where the tool is applied, such as hexagonal or cylindrical shapes. Shank: The cylindrical part where no thread is cut (does not exist in fully threaded bolts). Thread: The part where spiral grooves are cut. The “designation” when ordering is expressed as “Thread Diameter (M) x Length (L).” For example, “M10×50” means the outer diameter of the thread is 10mm and the length under the head (length excluding the head) is 50mm. Misunderstanding this is the biggest cause of ordering errors, so caution is required. You may have seen markings like “4.8” or “10.9” on the head of a bolt. These are important indicators showing the bolt’s “Tensile Strength” and “Yield Point (Proof Stress).” ...