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White Papers


Since 1948, SPIROL has been providing technical expertise in fastening, joining and assembly to the world's leading manufacturers.  Browse through these examples of our Solution Engineering White Papers.


Coiled Spring Pins
Coiled Spring Pins Offer a Unique Balance of Strength and Flexibility [+]

Easily recognized by its unique 2¼ coil cross section, Coiled Pins are retained by radial tension when installed into the host component, and they are the only pins with uniform strength and flexibility after insertion.

To read more, click here.

How to Design Assemblies That Use Coiled Pins for Locating and Alignment [+]

To achieve optimal alignment when using Coiled Pins, two primary design elements must be adhered to:
1) The hole diameters in the host and mating component must be correctly sized to achieve the desired interference and accuracy of alignment.
2) The engagement length of the Coiled Pin in the component providing primary retention must be no less than 60% of the pin’s overall length.

To read more, click here.

How to Design the Optimum Hinge [+]

There are two primary types of hinges: 1) a free fit hinge has little to no friction or drag when the latch or handle is rotated. Hinge components are “free” to rotate independent of one another, and 2) a friction fit hinge requires interference to prevent free rotation of components relative to one another. Depending on design intent, resistance can vary from a slight drag to a value sufficient to maintain the fixed position of components anywhere in their full range of rotation. This White Paper provides essential design guidelines for Engineers to achieve optimum long-term performance of both types of hinges.

To read more, click here.

How to Install a Coiled Spring Pin [+]

Coiled Pins were designed with assembly in mind. They are easy to install, and there are several options available for how to insert them into an assembly. This White Paper provides an overview of the Coiled Pin installation options: hammer, manual press, air hammer, and automatic installation equipment. Additional considerations like custom fixturing and spring-loaded alignment pins are also addressed. 

Read more on How to Install a Coiled Spring Pin

How to Properly Pin a Gear and Shaft Assembly [+]

This informative White Paper provides essential design guidelines to achieve the maximum strength of a pinned system and prevent damage to the assembly.  Design guidelines are provided for both 1) the shaft and hub, and 2) the pin.

To read more, click here.

How to Remove a Coiled Spring Pin [+]

Coiled Pins are serviceable fasteners that can be removed without damaging their host components, if done properly. This White Paper provides instructions for removing Coiled Pins from through holes as well as blind holes.

Read more on How to Remove a Coiled Spring Pin

How to Select the Proper Diameter and Duty of a Coiled Spring Pin [+]

This White Paper provides the fundamental guidelines for determining the optimum balance between strength and flexibility of the Coiled Spring Pin that will result in the prolonged net life of the assembly.

Read the complete White Paper about selecting the proper diameter and duty of a Coiled Spring Pin.

The Impact of Clearance on the Shear Properties of Coiled Spring Pins [+]

SPIROL has identified common design/manufacturing errors which reduce the strength of pinned joints. These features include, but are not limited to, counterbores, countersinks, and gaps between mating components. This White Paper quantifies the effects that clearance between the shear plane has on the strength of a pinned joint.

Read the complete White Paper here.

What's the Difference Between Alloy and Carbon Steel Coiled Spring Pins [+]

Carbon steel and alloy steel are the most cost effective and versatile materials available for use in Coiled Pins. Both materials provide similar mechanical properties and should be viewed as equivalent for Engineers from a performance standpoint. This white paper illustrates why and where these materials are used.

Read more on the Difference Between Alloy Steel and Carbon Steel Coiled Spring Pins 

Why Pins Walk and How to Ensure that Doesn't Happen [+]

Lateral movement of installed pins, commonly referred to as 'walking’, can occur with any pin in a dynamic application if proper design guidelines are not followed. This includes rigid Solid Pins as well as Slotted and Coiled Spring Pins. Although any kind of pin can walk, the causes may be different for each style. This White Paper will address common causes for lateral movement and offer design guidelines to avoid the condition.

Read more about Why Pins Walk and How to Ensure that Doesn't Happen.

Compression Limiters
How to Ensure Bolted Joint Integrity When Using a Compression Limiter in a Plastic Assembly [+]

Compression Limiters are used to protect plastic components in bolted joints and maintain a threaded fastener’s clamp load by eliminating plastic creep.  To function properly, bearing surface beneath the bolt’s head must extend over the Compression Limiter to contact the plastic component.  This White Paper explores several methods to ensure sufficient bearing surface under the bolt’s head while considering the individual component cost, ease or complexity of assembly, and the overall cost of each configuration to determine which method is best suited for each particular application.

Read the complete White Paper on how to ensure bolted joint integrity when using a Compression Limiter in a plastic assembly.

Compression Limiters and Threaded Inserts
How To Properly Mate Compression Limiters and Threaded Inserts in Plastic Assemblies [+]

In applications where the mating component is also plastic, a Compression Limiter is necessary to avoid the creep or stress relaxation in the mating component from reducing the frictional load in the threaded joint.  This White Paper provides design guidelines on how to properly mate Compression Limiters and Threaded Inserts to ensure the desired joint integrity over the life of the product.

To read more, click here.

Cosmetic Pins
Measurement Techniques for the Inspection of Series 550 Coiled Pins for Cosmetic Cases [+]

SPIROL® Series 550 Cosmetic Coiled Pins were designed specifically to be used as hinge pins in cosmetic cases.  Considering the configuration of the pin and the fact that it is a functional spring, care must be taken when measuring the pins so as not to skew the measurement results.  This White Paper will walk you through how to measure the key characteristics of a Series 550 Cosmetic Coiled Pin as well as recommend the proper measurement equipment.

To read more, click here.

Disc Springs
How Deflection Range Affects the Performance of Disc Springs [+]

Deflection of Disc Springs has a major impact on the performance and life of Disc Springs in both static and dynamic applications.  Designers need to consider factors affecting performance and life of the Disc Spring to maximize the potential of a Disc Spring in their design.

Read more about Disc Spring deflection.

How to Calculate the Estimated Fatigue Life of Disc Springs [+]

Disc Springs are conically-shaped washers designed to be axially loaded. They can be used individually or assembled into stacks to achieve the desired force-deflection characteristic required for the application. Since deflection of a Disc Spring at a given load is predictable, it is possible to calculate force and stress levels within the Disc. This paper focuses on the use of Disc Springs and how to estimate fatigue life in dynamic situations. 


How to Determine the Proper Disc Spring Stack Configuration [+]

Disc Springs are preferred over other springs when used in critical applications such as safety valves, clutch & brake mechanisms for elevators, and supports for industrial pipe systems due to their predictability, reliability and unparalleled fatigue life. They can be used individually or in stacks to achieve the desired force-deflection characteristic. Learn about the different methods of stacking, and how to determine the proper stack configuration for your application.

Read more about How to Determine the Proper Disc Spring Stack Configuration

The Difference Between Disc Springs and Belleville Washers [+]

While the terms Disc Springs and Belleville Washers are often used interchangeably, there are several important technical differences that should be clearly understood by Design Engineers. This White Paper details the differences between Disc Springs and Belleville Washers, and why Disc Springs may be more beneficial for your assembly – especially when subjected to dynamic loading.

Read about The Difference Between Disc Springs and Belleville Washers

Finishes and Coatings
Features and Benefits of ArmorGalv Thermal Zinc Diffusion [+]

SPIROL is pleased to offer ArmorGalv®, a Thermal Zinc Diffusion coating, as a standard finish option for their engineered fasteners.  This uniform deposition coating is poised to revolutionize the industrial fastener market with 1,000+ hours of corrosion resistance, no risk of hydrogen embrittlement, and no insignificant surfaces!

Download the ArmorGalv® White Paper.

Inserts for Plastics
How to Maintain Joint Integrity When Converting from Metal to Plastic [+]

Inserts for Plastics allow designers to replace machined and cast metal components with plastic to achieve significant cost and weight savings without any loss of joint strength - even in demanding applications. Threaded Inserts can be installed with heat or ultrasonics, they can be molded-in, pressed-in, or tapped into the hole. The challenge is for Engineers to choose an Insert that meets the performance and assembly requirements of the application. This article describes how Inserts for Plastics work, and provides design guidelines for the plastic host components to ensure that the completed assembly meets the desired expectations.

To read more, click here.

Installation Equipment
Heat Versus Ultrasonic Installation [+]

This informative document analyzes the differences between heat and ultrasonic installation of Threaded Inserts into plastic assemblies. In addition to detailing the advantages and disadvantages of each installation method, this White Paper also provides essential information as to how one can be sure that the Threaded Insert was installed properly into the assembly.

To access the White Paper, click here.

Vibratory Feeder Noise Reduction [+]

The effects of noise can have damaging consequences and efforts should be made to minimize noise exposure.  Reduction of noise produced by vibratory feeders is one area that can significantly reduce noise exposure in the workplace.

The SPIROL Series 2000 Vibratory Feeder is quieter than conventional vibratory feeders.  Empirical data to support this claim was gathered by conducting comparison testing between a conventional square drive and a SPIROL Series 2000 drive.  Measurements and analyses were performed by Noise Control Engineering (NCE) of Billerica, Massachusetts.  The same bowl was used for testing on each drive. Noise readings were taken with an empty bowl, plastic bottle caps and metal coiled pins.  Consistent feed rates were maintained between the Series 2000 and the square drive for both the caps and the pins.

Four measurements around each vibratory feeder were taken and averaged in order to compare the square drive to the Series 2000.

To read more, click here.

How to Control Shim Tooling Costs [+]

SPIROL has several manufacturing methods that eliminate or greatly reduce your tooling expenditure.

Shim tooling costs are one of the quickest ways to drive a prototype or short-run production project over budget.  SPIROL has several manufacturing methods that eliminate or greatly reduce your tooling expenditure.  Whether your project is for prototype, short run or long term requirements, SPIROL has a solution to minimize your installed component costs by controlling tooling costs.  This article describes some of SPIROL’s production technologies to help you determine which method is best for you.

To read more, click here.

The Advantages of Using Edge Bonded Shims [+]

Laminated Shims have peelable layers of metal which are removed until the Shim has the proper thickness. They are built up from layers of precision gauge metal foil. Layers are bonded into a rigid structure that appear and function as a solid sheet or plate. In this document you will read about two types of Laminated Shims: Surface Bonded and Edge Bonded Shims, and how Edge Bonded Shims provide solutions to reducing assembly times, minimizing costs, and improving safety.

Read more on the use of Edge Bonded Shims.

The Advantages of Using Shims in the Oil and Gas Industry [+]

Precision Shims are used in a variety of applications typically seen in the Oil & Gas industry. They can provide cost and labor reduction benefits throughout the life cycle of the equipment from assembly to installation to refurbishment and retrofitting.

Read about The Advantages of Using Shims in the Oil and Gas Industry

Slotted Pins
The Advantages of SPIROL Standard Slotted Pins vs. ISO 8752 [+]

Slotted Spring Pins, sometimes referred to as Roll Pins or Split Pins, are general purpose low cost pins commonly used in various fastening applications. While both SPIROL Standard Slotted Pins and ISO 8752 Slotted Pins can be used effectively in certain assemblies, SPIROL Standard Slotted Pins are far superior in form, fit and function – including in the installation process. This White Paper details why the SPIROL Standard is the Slotted Spring Pin of choice!

Read more about The Advantages of SPIROL Standard Slotted Pins vs. ISO 8752

Solid Pins
Fastening Techniques for Plastic Housings [+]

This White Paper addresses the advantages and disadvantages of the following fastening methods used to assemble plastic components: solid pins, adhesives, screws, bolts, and snap-fit joints.

Read Fastening Techniques for Plastic Housings

Solid Pin Retention Features [+]

Solid Pins are commonly used as a permanent fastener in a wide range of applications. They are retained by the harder Solid Pin displacing material in the softer host component(s).  There are several types of Solid Pin retention features.  This White Paper describes the common types of retention features and can serve as a reference tool when designing a new product.

Read Solid Pin Retention Features

The Difference Between Cold Headed and Machined Solid Pins [+]

The objective of this paper is to educate designers about the differences between cold heading and machining so that they understand how to design a Solid Pin that optimizes performance and reduces total manufactured cost of the assembly. 

Read more about cold headed vs machined solid pins.

Solid Pins, Slotted Pins and Coiled Pins
How to Choose Fasteners that Maximize Assembly Life [+]

An assembly can be held together many different ways.  The challenge for the Design Engineer is to choose a method that provides the highest quality joint with integrity over time at the lowest manufacturing cost.       For many applications, a self-retaining pin is the winning solution.  The difficulty is selecting the proper pin with the appropriate strength and flexibility for the application.  This Technical White Paper reviews the advantages and disadvantages of common types of pins, as well as provides guidelines as to when to use each type in certain applications.

To read more, click here.

How to Select the Proper Pin for Your Application [+]

Pins are some of the most common types of fasteners in modern manufacturing. Designers can optimize the performance and total manufactured cost of a product by selecting the proper pin for their product. In order to do this, it’s critical that fastener options are considered early in the design stages. The most important step in selecting the proper pin is to evaluate the application in detail and establish performance requirements.

Read How to Select the Proper Pin for Your Application

Solid Pins, Slotted Pins, Coiled Pins and Spacers
Fastening Solutions for Medical Devices [+]

Even though the application requirements do not justify it, fasteners used in medical devices are usually specified as extremely tightly toleranced parts.  In addition, due to the unfamiliarity of the various fastener industry standards and associated manufacturing processes, Engineers frequently tie the hands of the fastener manufacturer into using high-cost manufacturing processes to  meet the specifications.

This White Paper focuses entirely on what designers and manufacturers need to know, avoid and do when it comes to pinning and spacing requirements in medical devices.

To read more, click here.

Spring Pins
How to Maximize Retention of Spring Pins [+]

When proper design guidelines are followed, companies can take advantage of the many benefits that Spring Pins offer. They significantly reduce the total cost of the assembly, lower insertion forces and improve the life of an assembly by absorbing shock and vibration. This White Paper walks through a handful of simple – but essential - design guidelines for Engineers to ensure assemblies have reliable robust joints with excellent retention.

To read more, click here.

Which Austenitic Stainless Steel Spring Pin is Best for Dynamic Loading? [+]

Although there are many advantages to using Spring Pins, it is important to understand the design features between Slotted and Coiled Spring Pins - particularly for critical applications and those subjected to dynamic loading. This White Paper details the specific differences between both Slotted Spring Pins and Coiled Spring Pins and explains which Spring Pin is best for dynamic loading.

Read more about Which Austenitic Stainless Steel Spring Pin is Best for Dynamic Loading.

Stainless Steel
Comparative Analysis of Stainless Steel and Carbon Steel Fasteners [+]

Corrosion of stainless and carbon steel are very different. This paper will provide information regarding general attack or surface corrosion as this is often a primary consideration when selecting fastener material.

To read more, click here.

Type 316 Stainless Steel Comparison [+]

The versatility of Coiled Spring Pins often times makes them the ideal fastener to meet the specific engineering and economic objectives of pinning applications.  They are available in a wide variety of sizes, duties, finishes, and materials.  Amongst the materials used to manufacture Coiled Spring Pins, stainless steel is often required for its high corrosion resistance.  Coiled Spring Pins are most often manufactured from Type 302/304 and Type 420 stainless steel, but Type 316 is also available and is typically selected for its superior corrosion resistance.  This paper takes a closer look at how Type 316 compares to Type 302/304, and discusses various applications and environments where it offers an advantage.

To read more, click here.

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Alignment Dowels
How to Choose the Most Cost Effective Alignment Dowel
Coiled Spring Pins
Clever Seam Design Makes the Coiled Pin Perfect for Hinges
How To Improve Product Design and Manufacturability with the Coiled Pin
How to Reduce Assembly Costs with Coiled Spring Pins
Measurement Techniques for the Inspection of Coiled Spring Pins
The Importance of the Insertion Quill when Installing Coiled Spring Pins
The Pin
Fasteners and Automation
Choosing the Proper Fastener when Automating
Inserts for Plastics
Insert Material Brass versus Stainless Steel
The Impact of RoHS and DFARS (The Berry Amendment)
Adjustable Bearing Preload Solutions
Shims? Make Mine Laminated!
Slotted Spring Pins
The Advantages of Using Light Duty Coiled Pins Versus Slotted Pins in Soft Materials
Solid Pins and Spring Pins
Hole Preparation for Press Fit Pins
Sourcing a Fastener
Lowest Installed Cost
Spring Pins
Slotted Pin Inflexibility Leads to Failure
Stainless Steel
Passivation: Is it Really Necessary?