{"id":5719,"date":"2026-09-11T10:00:49","date_gmt":"2026-09-11T01:00:49","guid":{"rendered":"https:\/\/ohtavn.com\/?post_type=media&p=5719"},"modified":"2026-09-09T12:37:51","modified_gmt":"2026-09-09T03:37:51","slug":"what-is-the-strength-classification-of-screws","status":"publish","type":"media","link":"https:\/\/ohtavn.com\/en\/media\/what-is-the-strength-classification-of-screws\/","title":{"rendered":"What is the strength classification of screws? Standards and selection criteria that manufacturers should know"},"content":{"rendered":"
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Introduction<\/h3>\n<\/div>\n
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On a manufacturing floor, the failure of a single “screw” can destroy the reliability of an entire product and, in some cases, lead to catastrophic accidents. Especially for industrial machinery with high vibration or infrastructure equipment used in harsh environments, selecting the appropriate “Strength Class” is a top priority in design and procurement.<\/p>\n<\/div>\n

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In this article, we provide a comprehensive guide for manufacturing executives, procurement managers, and on-site engineers, covering everything from the basics of screw strength classes to essential calculation formulas and the increasingly popular IoT-driven fastening quality management. Furthermore, we will touch upon the procurement environment in Vietnam, where industrialization is rapidly progressing, and introduce how Ohta Vietnam’s solutions balance cost optimization with quality assurance. We hope this article serves as a guide for safe and efficient fastening design.<\/p>\n<\/div>\n

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Basics of Strength Classes and the Importance of International Standards<\/h3>\n<\/div>\n
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What the Numbers Mean: Tensile Strength and Yield Point<\/h4>\n<\/div>\n
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Numbers such as “4.8” or “10.9” marked on screw heads or packaging represent the “Strength Class.” These numbers serve as a global language indicating how much load the screw can withstand.<\/p>\n<\/div>\n

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For example, in the notation “10.9,” the first number “10” indicates the Nominal Tensile Strength, meaning it can withstand up to 1,000 N\/mm\u00b2. The following “.9” indicates that the Yield Point (or proof stress) is 90% of the tensile strength. In other words, if a load of 900 N\/mm\u00b2 or more is applied, the screw will undergo “permanent deformation” and will not return to its original shape. Fastening with over-specified parts without this knowledge leads to increased costs, while under-specified parts significantly increase the risk of breakage.<\/p>\n<\/div>\n

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Alignment between Japanese Industrial Standards and International Standards (ISO)<\/h4>\n<\/div>\n
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While the Japanese Industrial Standards (JIS) are widely referenced in many manufacturing sites today, most are compliant with the international standard ISO 898-1. In today\u2019s world of global supply chains, understanding these international standards is essential.<\/p>\n<\/div>\n

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Particularly when procuring parts from overseas hubs like Vietnam, verifying that quality control is based on JIS or ISO\u2014rather than just local standards\u2014is the key to maintaining “Japanese Quality.” At Ohta Vietnam, we handle only products that strictly comply with these international standards, accurately bringing Japanese design intent to life.<\/p>\n<\/div>\n

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The Science of Fastening Design: Calculations and IoT Enhancement<\/h3>\n<\/div>\n
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Calculation of Tightening Torque and Strength Design<\/h4>\n<\/div>\n
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The most important factor in screw selection is controlling the “axial force” (the clamping force). To achieve proper fastening, the following basic formula is used:<\/p>\n<\/div>\n

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$$T = K \\cdot d \\cdot F$$<\/p>\n<\/div>\n

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Here, $T$ represents the tightening torque (N\u00b7m), $K$ is the torque coefficient, $d$ is the nominal diameter of the screw (mm), and $F$ is the axial force (N). Since the torque coefficient $K$ varies greatly depending on the lubrication state of the screw surface and the material, the management of this coefficient becomes more critical as the strength class of the screw increases.<\/p>\n<\/div>\n

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Visualizing Fastening through IoT Technology<\/h4>\n<\/div>\n
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In recent years, Ohta Vietnam has been focusing on Smart Factory implementation using IoT. While conventional quality control mainly relied on torque checks via sampling inspections, the introduction of IoT-compatible digital torque wrenches allows for the real-time collection and analysis of all fastening work data.<\/p>\n<\/div>\n

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This ensures traceability regarding “who tightened it, when, and with how much force,” providing digital proof that optimal fastening has been performed based on the strength class. This offers a powerful competitive advantage, especially in sectors requiring high safety, such as automotive and precision equipment.<\/p>\n<\/div>\n

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Key Data: Statistics on Screw\/Fastener Market and Quality<\/strong><\/p>\n

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