Why fastener redesign is often necessary, and the critical factors to make it successful

Redesigning fasteners is a complicated process and requires expertise and understanding when the decision has been made to do so

By Steve Adkins October 12, 2023
Courtesy: Optimas Solutions


Learning Objectives

  • Learn the basics of redesigning fasteners, including pros and cons.
  • Understand what things to look for in the process to ensure success.
  • Review the benefits of considering redesigning fasteners in a product.

Fastener insights

  • Several different considerations and actions need to be taken when redesigning fasteners successfully, and answering questions like “why” and “how much” can help obtain the answers.

  • Fasteners should be tested and validated, and must meet basic safety requirements.

Fasteners play a critical role in holding together equipment ranging from automotive products to wind turbines. There are times when fasteners do not meet performance standards and require redesigning. Redesigning fasteners is a complex process that requires a thorough understanding of the current design’s performance expectations, operating conditions and potential design flaws.

Making the decision to redesign fasteners can be daunting when one considers how critical fasteners are to a product or piece of equipment and the financial, logistical and operational impact it may have on future products. Manufacturers should carefully explore why a redesign is a good idea before proceeding.

There are several reasons why an engineer or manufacturer decides to redesign fasteners, including:

  • Changes in the application or environment in which fasteners are used.

  • The need to improve performance.

  • An update design on a current model is necessary.

  • There is a desire to reduce cost and/or improve efficiency.

Regardless of why a manufacturer wants to redesign fasteners in a product, a good fastener supplier can help make the decision easier so it is always important to get them involved early in the process, particularly when it comes to highly engineered equipment.

Understanding the fastener problem, goals are key to redesign

Redesigning fasteners requires a thorough understanding of the problem and goals for the redesign. That is why discovery in these areas is key to the redesign process in the very beginning.

First, a designer or manufacturer needs to determine the requirements of the fasteners, brainstorming potential design changes and evaluating the manufacturability, aesthetic value and price of each design. The best solution is then chosen and tested before being implemented in production. Monitoring the performance of the new fastener during testing and making further refinements, if needed, is essential to ensure the redesign performs better for users and the company.

Customers should have access to a manufacturer with quality assurance lab services that help in this process. Knowing how critical a fastener can be in a design is a big part of the process and providing the testing to ensure success is especially important.

Figure 1: In 2021, Optimas Solutions added a Chun Zu four-die, four-blow cold header manufacturing machine that increased its capabilities to deliver larger format diameter fasteners and free up existing cold headers to provide more onshore support for smaller fasteners. Courtesy: Optimas Solutions

Common performance requirements fasteners can fail to meet

In 1998, the National Institute of Standards and Technology discovered that one of the ship Titanic’s smallest components — the 3 million wrought iron rivets used to hold the hull sections together — were the reason the ship sank. The metallurgical properties of the rivets made them brittle when exposed to very cold temperatures, strongly suggesting that Titanic’s collision with the iceberg caused the rivet heads to break off, popping the fasteners from their holes.

Understanding the performance requirements for fasteners being designed into a product or piece of equipment is critical as in the case of the Titanic. Some of the simplest specifications or manufacturing practices of a fastener can cause catastrophic performance problems. That is why it is important to understand what they are and guard against them in advance.

Regarding nuts and bolts, the most common performance requirements that they fail to meet include inadequate strength grade, poor plating that results in corrosion or rust and hydrogen embrittlement that can cause the fasteners to break under stress. Additionally, thread issues and poor production quality can lead to the fasteners failing to meet their intended purpose.

In terms of washers, common problems include inadequate plating, hydrogen embrittlement, incorrect material selection and manufacturing issues. Fittings also often fail to meet material and manufacturing requirements.

Understanding these potential risks can be critical to one’s redesign efforts and needs to be well thought through during the process.

Understand the environmental factors that may affect fastener performance

Just like Titanic, understanding how environmental factors such as temperature, humidity, exposure to corrosive chemicals and ultraviolet exposure along with potential design flaws can affect the performance of fasteners is a critical step in the redesign process. It is essential to consider these factors when redesigning fasteners, particularly in industries such as electric vehicles (EV), wind turbines or manufacturing equipment.

For example, given the distinctive nature of the operation of EVs and fastener performance needs, designers must consider corrosion issues, weight displacement needs and fastener strength requirements.

These “environmental” factors need to be fully explored and understood in each application of fastener technology during the redesign process.

Simplified, streamlined fastener with a redesign

As manufacturers and those on the engineering side strive to reduce costs by reducing the cost of materials and improving operational efficiencies, a redesign can be instrumental in helping address these aspects of product production. During the redesign process, it is important to think these factors through.

For example, moving to lightweight materials, such as going from steel to lighter-weight metals, can reduce weight in areas such as in nonstructural rivet applications.

In larger bolted applications, working with the manufacturer to understand the application, using BOLTCALC software and even requiring durability testing are a few ways to verify weight reduction projects.

Also, depending on the critical nature of the fastener, the diameter and grade can be reduced to save weight. Rationalization and/or consolidation programs can be completed to reduce the number of fasteners in a product as well.

Assembly and installation requirements can impact the efficiency and cost of installation and manufacturing processes, even at the plant level. There are one-sided drive systems, which can reduce labor on the assembly line and other nontorque drive products. These fasteners are usually more expensive but reduce quality issues, usually install faster and deliver repeatable clamp loads.

New trends in the fastener industry

There are various tools and analyses available to help identify and redesign a fastener, including computer-aided design software like SolidWorks, BOLTCALC for fastener analysis and assembly tools to install the fastener.

BOLTCALC is a valuable tool in diagnosing material and performance flaws in fasteners that need addressing in a redesign. It allows fastener makers to theoretically calculate clamp load and torque by adding variables such as plating, material and other inputs. Using this software allows engineers to identify potential issues before production and can ensure the new fastener meets the products’ necessary performance requirements.

Figure 2: A lathe smooths a fastener during production at Optimas. Courtesy: Optimas Solutions

The fastener industry is constantly evolving. Automation, new thread and drive designs, nut shapes and sizes, nonferrous material for EV applications, nontorque related assembly processes and assembling tooling for small fasteners are a few of the areas where fastener innovation is taking place every day.

Meeting performance requirements

Various testing and validation methods, such as tensile testing, torque testing, vibration testing and environmental testing should be used to ensure the redesigned fastener will perform optimally. These tests evaluate performance and durability under different conditions and ensure that they meet industry standards. In addition to these testing processes, user feedback and data are also crucial in the fastener redesign process.

Working with a fastener maker that has comprehensive and effective testing and quality analysis capabilities is important to addressing this issue. An integrated testing approach enables engineers to test anything from tensile strength, plating thickness and even small screw drives easily and effectively.

How savings can be achieved

Regardless of the reason for a redesign, cost reduction is always a goal of the process. As with the actual design of a product, it is important to understand early in the process the potential cost implications with changes in design.

Cost implications can vary and will depend on the manufacturer’s requirements. These can include reducing quality issues, speed of manufacturing and material that expands the fastener and product’s useful life. Also, cost-saving can be achieved by changing the fastener design and characteristics to better meet real use-case requirements.

Understanding these implications early in the process can eliminate issues and potential pitfalls down the road.

To ensure safety and performance can achieve production cost reductions, a fastener redesign may be the right move. With the right tools, materials and experts and, most of all the right partner, this process can lead to significant improvements and cost savings.