In the world of manufacturing, a single screw, just a few millimeters in size, can have a significant impact on the overall quality, cost, and even the delivery time of a product. A screw is not merely a fastening component; it is a “linchpin of machinery” that is involved in all processes of design, procurement, production, and maintenance.

Especially in recent years, with the diversification of products, shorter delivery times, and the advancement of overseas procurement, the optimal use of “standard screws” and “custom screws” has become more important than ever. Standard screws offer low cost and stable supply, but they also carry the risk of significantly compromising performance if they do not match the product or structure. On the other hand, custom screws can be optimized for required performance, but cost and lead time often become issues.

This article provides practical judgment criteria and optimization perspectives that designers, procurement managers, and manufacturing engineers can implement on-site to address this “screw selection dilemma.” We will organize the differences between custom and standard screws, their manufacturing processes, and cost-performance considerations, and provide a practical explanation that includes a perspective rooted in the field, particularly in procurement and manufacturing in Vietnam.

We hope that this article will provide you with practical hints on how reviewing your screw selection can achieve both improved product reliability and cost reduction.

Screws, often used inside products, are not visually prominent. However, in reality, they are a crucial element that influences the assembly precision, performance, and safety of a product. It is not uncommon for the choice of a single screw to significantly alter performance aspects such as durability and vibration resistance.

The selection of a screw is not simply a task of applying a standard; it affects the overall cost structure, delivery time management, and quality assurance of the product. For example, choosing an unnecessarily high-performance custom screw can lead to over-engineering, while a standard product that fails to meet the required performance can lead to product trouble.

Judgment at the design stage is particularly important for screw selection. By quickly identifying “whether a standard product can be used” or “which parts should be custom-made,” it is possible to prevent rework and cost increases in later processes. This is an area where collaboration between design and procurement is required.

For purchasing departments and maintenance sites, screw selection is a critical issue related to operational costs and stable supply. Utilizing standard products allows for procurement from multiple suppliers and efficient inventory management.

This article provides a practical explanation of how to properly use custom and standard screws from both technical and cost perspectives. The target audience includes everyone involved in screw selection, such as designers, purchasing managers, and manufacturing engineers. We particularly aim to provide practical selection hints for manufacturing sites in Southeast Asia, including Vietnam.

Standard screws are off-the-shelf products designed and manufactured in accordance with standards such as JIS (Japanese Industrial Standards) and ISO (International Organization for Standardization), and are widely distributed in the market. Since their sizes and thread shapes are standardized, they are compatible with any manufacturer, and their high procurability is the greatest advantage.

Due to mass production systems, their prices are low and they are easy to manage in inventory. Therefore, standard products are recommended, especially for consumable parts with high replacement frequency and for general assembly applications.

Custom screws are made-to-order fastening components designed and manufactured from scratch to match the application or structure. Since their shape, dimensions, material, and surface treatment can be freely configured, they can meet needs such as “standard products lack sufficient performance” or “installation space is limited” (Reference: Neji Labo).

For example, they are used in situations requiring high precision and high reliability, such as in medical equipment, analytical instruments, and aircraft parts.

The decision of whether to use standard or custom screws must be made based on the product specifications and operating conditions. If design freedom is the priority, custom screws are the basic choice; if procurement cost and delivery time are more important, standard products are the way to go.

Furthermore, in cases with special requirements such as space-saving design, weight reduction, or heat/chemical resistance, product performance can be maximized by partially using custom screws.

The basic approach is to assume the use of standard products and introduce custom products only for parts that absolutely cannot be handled by standard ones. This approach makes it easier to achieve both product procurability and cost performance for the entire product.

In mechanical design as well, having this judgment criterion from the early stages of design enables the creation of high-performance products without compromising development speed or mass producibility.

Source_Japanese: Machine Design Map “Differences Between Standard and Custom Parts in Component Selection and Design Points”

The development of a custom screw begins with a hearing to determine the usage environment and performance requirements. To meet needs that cannot be realized with standard products, such as corrosion resistance, high torque support, or space-saving design, the dimensions, shape, material, and surface treatment are considered from scratch.

Based on these requirements, the design team performs structural design and strength calculations, and creates a detailed model using 3D CAD. The precision of this initial design greatly affects the quality and functionality after cutting.

Source_Japanese: Neji Labo “What is the Process for Special Screw Production? The Merits and Applications of Made-to-Order Screws”

In the machining process, cutting is performed using lathes and machining centers, followed by grinding finishing as necessary. For applications in high-precision medical and electronic equipment, even errors of a few microns are not permissible.

Afterward, depending on the usage environment, surface treatments such as zinc/nickel plating, PTFE coating, and PVD treatment are applied to add corrosion and abrasion resistance.

The advantage of custom screws lies in their ability to handle “high-mix, low-volume” production. Even for specifications that were considered inefficient with conventional mass-production thinking, it is possible to manufacture them rationally with processing equipment that supports small lots and flexible process design.

This kind of response is particularly valued in fields such as development products, prototypes, and special-purpose equipment.

Custom screws may seem more expensive than standard products at first glance, but this is not necessarily the case when looking at the total cost. In many cases, it is possible to reduce costs over the entire life cycle, such as by extending the product’s lifespan, reducing the number of parts, and improving maintainability.

The cost of screws may only be a few percent of the total product cost, but the loss incurred when trouble occurs can be dozens of times greater. A perspective that considers “necessary costs” and “future risks” from the initial design stage is important.

Standard screws are produced based on international standards such as JIS and ISO, and mass production systems are in place. Therefore, the unit price per screw is low, making it possible to significantly reduce procurement costs.

Furthermore, since they are always available as stock items, delivery times can be shortened even for sudden design changes or arrangements for replacement parts, contributing to the stabilization of the manufacturing schedule.

Standard screws comply with common standards like JIS and ISO, and numerous manufacturers both domestically and internationally produce them to the same specifications. This makes it easy to secure multiple procurement routes without depending on a specific supplier.

This high compatibility also serves as a hedge against risks such as disasters, price fluctuations, and transportation delays, and is an element that supports the stability of the entire supply chain.

Moreover, even when expanding products globally, screws of the same standard can be procured in various parts of the world, which facilitates local assembly, maintenance, and replacement.

When considering equipment maintenance and after-sales service, adopting standard screws offers significant advantages. Commercial products can be replaced immediately on-site, requiring no special tools or skills.

In terms of inventory management, it is easy to standardize parts across multiple models, leading to a reduction in the number of maintenance parts and savings in inventory space.

By designing parts to match the dimensions and shapes of standard screws from the outset, the use of custom parts can be minimized. For example, simply aligning design dimensions with commonly available bolt lengths and screw pitches can reduce the burden of manufacturing and procurement.

Especially for mass-produced products and equipment where maintainability is a priority, the attitude of “first, can we handle this with a standard product?” is the key to optimizing cost performance.

When selecting a screw, it is crucial to first clarify its usage environment. The required material and surface treatment vary greatly depending on environmental conditions such as high temperature, high humidity, corrosive gases, vibration, and chemical exposure. For example, a chemical plant may require a coating with chemical resistance, which can only be provided by a custom screw.

Another important selection criterion is whether the screw can meet the required strength against load conditions such as tension and shear. If it can be handled within JIS standards, a standard product is used; otherwise, customization becomes a consideration.

If there are restrictions on the space where the screw is to be installed or on the surrounding structure, the size of a standard screw may not be sufficient. In such cases, a custom screw with a modified head shape or an adjusted shank length may be necessary.

On the other hand, by “designing the structure to fit standard products” from the initial design stage, the use of custom screws can often be avoided. To optimize cost and delivery time, one should first consider a solution using standard dimensions.

The basic strategy in screw selection is to “use standard products as much as possible, and introduce custom screws only when standard specifications cannot meet the requirements.” An error in this judgment can lead to increased manufacturing costs and supply troubles. Therefore, it is necessary to make a comprehensive decision after sharing information not only with the design department but also with the procurement and quality departments.

For example, even if costs are temporarily suppressed by using a standard product, if assembly problems occur due to specification mismatches, or if replacement is required due to unexpected wear or damage, the total cost will actually increase. To avoid such risks, a judgment that considers the life cycle cost from the initial design stage is required.

In manufacturing in emerging countries like Vietnam, screw procurement presents unique challenges. The products available locally often include non-standard items or those with quality variations, leading to situations where the specifications envisioned at the design stage do not match the actual procured items.

Particularly in high-mix, low-volume production or at the prototype stage, lot restrictions and delivery delays for standard products can become obstacles, creating risks of design changes or part substitutions.

OHTA Vietnam’s screw solutions address these local challenges. The company has a procurement network closely tied to the local area and advanced design and manufacturing know-how regarding custom screws, enabling production from small lots and short delivery times.

Especially in situations with prototypes or special-purpose parts where “there are no standard products” or “procurement from Japan takes too long,” they provide flexible solutions through local support.

Ohta VietNam’s strengths go beyond simply supplying screws. They have a system in place to support the entire component selection process, including technical support at the design stage, advice on material selection, and proposals for surface treatment specifications.

They are also well-versed in Vietnam’s domestic quality standards and regulatory information, and can provide drawing reviews and quality assurance support in cooperation with their head office in Japan. This helps prevent drawing communication errors and specification mismatches between Japan and Vietnam, thereby increasing procurement stability.

Screw selection is not just about choosing a part; it is a critical decision that affects the cost, quality, and delivery time of a product. Both standard and custom products have their own advantages and limitations, and discerning and appropriately using them is the key to design optimization and improved cost performance.

While custom screws offer excellent flexibility in terms of performance, they also come with risks related to delivery time and cost. Conversely, standard products are advantageous for procurement and maintenance, but their range of application is limited. It is necessary to understand these differences at the design stage and have a perspective that combines both as needed.

OHTA Vietnam supports the resolution of manufacturing site issues from both custom and standard screw perspectives. For companies facing challenges in procurement and manufacturing in Vietnam, they provide powerful solutions as a partner that offers integrated support for design, quality, and procurement.

Conclusion

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