Stronger, Simpler, Smarter: Why Slotted Tension Pins Outperform Coiled Pins

Rollpins®. Spring pins. Tension pins. Locking pins. Locking dowel pins. Slotted spring pins. ASME B 18.8.2. ISO 8752 (formerly DIN 1481). ISO 13337 (formerly DIN 7346).

You may recognize these names, but what do they all have in common?

The answer is they’re different terms for the same essential fastening component: the slotted tension pin.

In the world of fastening solutions, slotted tension pins have proven to be an indispensable component across industries. These hollow, self-locking cylinders simplify design, streamline assembly, and reduce production costs compared to alternative fasteners.

In industries as diverse as agriculture, railway, snow removal, mining, HVAC, OME, consumer products, and more, slotted tension pins enhance performance, reduce costs, and minimize long-term maintenance.

Let’s take a closer look at what makes slotted tension pins indispensable—and how they can benefit your application.

What is a Slotted Tension Pin?

Slotted tension pins are cylindrical fasteners with a longitudinal slot that allows them to compress when inserted into a hole. This design gives them a unique, self-locking quality that exerts radial pressure against the hole, creating a friction-based hold without the need for adhesives or secondary fasteners.

Unlike traditional fasteners that can loosen over time, these components exert continuous radial pressure that keeps the pin firmly in place, even in high-vibration environments.

Slot dimensions, outside diam­eters, and elastic limits are engineered so that this self-locking action is achieved in holes drilled to normal production tolerances. No reaming opera­tions are needed to ensure a tight fit. No second­ary operations are required to keep them in position.

Slotted tension pins are used in an extensive array of applications. They regularly function as fasteners, hinge pins, stop pins, assembly pins, and in myriad other roles. These tried and true all-purpose non-threaded fasteners can be used in stampings, castings, forgings, sintered metals, hard rubber, and plastics.

Their unique design enables them to outperform many traditional fasteners in various applications. Their flexibility and ease of use make them a preferred choice for engineers and manufacturers alike.

Advantages Of Slotted Tension Pins

Slotted tension pins stand out from traditional fasteners due to their unique design and functional benefits. Their adaptability makes them particularly well-suited for dynamic applications where components are subject to movement, vibration, or impact.

Here are some of the key advantages they offer.

Reduce Assembly Costs

Their hollow cylindrical design reduces assembly and production costs, particularly since these tension pins can be installed in a single operation. Because slotted pins are designed to compress upon insertion, they eliminate the need for additional threading, adhesives, or locking mechanisms. This results in a streamlined assembly process, reducing labor time and simplifying manufacturing workflows.

If a closed gap is a concern, metric ISO pins are designed never to have a gap close in the hole.

Efficient And Easy Installation

Slotted tension pins offer a straightforward installation process, accommodating multiple methods such as manual insertion, arbor presses, pneumatic tools, and automated assembly systems.

Unlike some other fasteners, slotted tension pins do not require specialized tools for installation and can be installed efficiently across various production environments for simple, economical assembly.

Their chamfered ends facilitate smooth entry into holes, eliminating the need for reaming or secondary operations. With generous hole tolerances, they reduce machining time and assembly costs.

Reduces Wear And Maintenance

Slotted pins help distribute loads evenly and flex under stress, effectively absorbing shock and minimizing wear on surrounding parts. This extends the lifespan of assemblies and reduces the need for frequent replacements or repairs.

Additionally, because slotted pins conform to the drilled hole rather than cutting into it like splined or notched pins, they minimize hole wear. This prevents the need for re-drilling and upsizing pins over time, maintaining the integrity of the assembly and further lowering maintenance costs.

Cost-Effective

Slotted tension pins offer significant cost advantages over solid pins, coiled pins, and other alternatives. Their lower per-piece cost combined with simplified installation reduces both material and labor expenses, making them the least expensive spring pin option.

Beyond initial savings, slotted pins deliver long-term cost benefits by eliminating the need for secondary fasteners, streamlining assembly, and minimizing component complexity.

They also afford great “in place” cost savings, reducing the total cost of assembling a product. Their ability to securely self-lock in standard drilled holes reduces the need for precise hole tolerances, cutting down on machining time, tooling costs, and overall production effort.

Additionally, because slotted pins adapt to slight variations in hole size, they help prevent rejections and waste associated with strict tolerance requirements, further driving down total manufacturing costs.

Weight Savings

Slotted tension pins provide substantial weight savings over coiled and solid pins by using a hollow, slotted design that reduces material volume compared to solid and coiled pins. Despite their lighter weight, they maintain strong holding power through radial tension, allowing engineers to achieve secure assemblies without unnecessary mass.

Additionally, because slotted pins can replace multiple fasteners in some designs, they further contribute to overall weight reduction in an assembly.

Superior Vibration Resistance

Unlike solid fasteners, slotted tension pins apply continuous outward pressure within the hole, ensuring a tight fit that resists loosening due to vibration. This makes them a preferred choice in applications like agriculture, construction, and waste management, where movement and impact can compromise traditional fasteners.

Strength And Load-Bearing Capabilities

Slotted tension pins are designed to provide superior strength and durability in demanding applications. Their construction from a single piece of hardened spring steel allows them to withstand high shear forces, making them a reliable choice for assemblies requiring a secure and load-bearing connection.

Their unique slotted construction and ability to exert continuous radial pressure make them stronger than a standard coiled pin. They provide a more rigid and stable fastening solution, making them ideal for situations where maintaining structural integrity is critical.

Can Be Doubled For Increased Strength

Slotted pins can be doubled by inserting one into another, typically a larger-diameter pin, to gain additional shear force. This significantly boosts the load-bearing capacity, preventing excessive stress on surrounding materials without the need for a solid pin, all while maintaining a lower weight than using a solid or coiled pin of the same diameter.

Many Size And Diameter Options

Slotted tension pins are the most versatile pins available, available in one of the widest ranges of sizes and diameters to accommodate countless applications. Whether for heavy-duty industrial machinery or delicate consumer products, there is a slotted pin to fit the specific requirements of the assembly.

Their availability in various wall thicknesses and lengths allows engineers to fine-tune performance characteristics such as flexibility, strength, and load distribution. This extensive range of options ensures that slotted pins can be easily integrated into existing designs or serve as direct replacements for other fasteners without requiring major modifications.

Slotted Pins As A Replacement For Other Fasteners

Slotted tension pins are an effective alternative to many traditional fasteners, streamlining designs and reducing component counts. They can potentially replace at least fifteen different fasteners to cut assembly costs and afford savings over time.

These are some of the fasteners that slotted pins can replace, and why they’re a superior option.

Keys

Traditionally used in mechanical assemblies to transmit torque, slotted pins provide a more uniform load distribution, reducing the risk of component fatigue and failure. Slotted pins demonstrate their ability to eliminate precision tolerances for faster and more cost-effective assembly.

Grooved Pins

Used in applications like ratchet wrenches, slotted tension pins offer superior flexibility and shock absorption. With their lightweight and high shear strength, they reduce stress on surrounding materials and extend tool life.

Rivet Shafts

Slotted pins offer a cost-effective alternative for light fastening applications by simplifying installation and eliminating the need for additional locking features. A flush, clean fit can be achieved without riveting or threading.

Cotter Pins

Often used in high-vibration applications, slotted tension pins provide a more secure hold without the risk of deformation or loosening. Assembly time is shorter, service life is multiple times longer.

Set Screws

Used in applications from medical to firearms, mechanical to electrical, slotted tension pins provide a more durable and maintenance-friendly solution that does not require having a hole tapped. Eliminating this operation avoids expensive reaming and thread tapping in applications.

Clevis Pins

Slotted tension pins hold firmly in clevis applications while allowing free movement of the attached component. For example, in a home workshop tool, a slotted pin secures a moving plate, allowing smooth motion without additional locking hardware.

Taper Pins & Headed Pins

Slotted tension pins eliminate the need for reaming, reducing labor time and simplifying installation in precision assemblies. They also remove more easily than taper pins, facilitating maintenance and part replacement. They are simply and inex­pensively driven in place, reducing the weight of an application.

Hub Connections

Used to secure gears and pulleys, slotted tension pins create a strong, vibration-resistant connection that prevents loosening over time. Slotted pins can simply be snapped into a molded slot to position sin­tered gear.

Dowel Pins

Frequently used in bearing assemblies, slotted tension pins provide a more forgiving fit by accommodating minor hole misalignments while maintaining alignment and stability. No reaming and no special locking is required.

Screws Or Bolts And Nuts

In linkage applications, slotted pins reduce weight and complexity while offering the same level of reliability. You don’t need additional fasteners such as external lock washers, flat washers, external tooth lock washers, or lock nuts in the assembly. This reduces the number of fasteners needed in a given application.

They may be used with a free fit in outer or inner mem­bers, depending upon product design requirements.

Rivets

Traditional rivets can fail at the clinched end due to vibration and repeated impact. Often used in electrical assemblies, slotted pins serve as guide shafts for spring-loaded interlock contacts, providing a more durable fastening solution that withstands operational stresses.

Material Options And Customizations

Among the thousands of standard applications for slotted pins, a few always demand unique customizations because of design requirements. To meet these diverse application needs, slotted tension pins are available in various materials and can be designed with unique characteristics to support your application’s needs.

Materials

Slotted pins are most commonly found in high carbon spring steel that is heat treated to achieve optimum shear strength in all standard parts. They are also available in work hardened 18-8 nickel chromium steel, 420 hardened stainless steel, and can be made with exotic alloys like 316 steel and Beryllium Copper.

These materials support different temperature tolerances and mechanical properties and can be engineered for extreme temperatures, magnetic resistance, or electrical conductivity.

Slot Designs

Tension pins can be manufactured with special slot designs per your specification, including semi-circle, wave, traverse wave, and trapezoid. Slot designs can be adjusted for specific load-bearing and flexibility needs.

Finishes And Plating

Unlike a coil pin, which cannot be coated on the inside of the coil, slotted tension pins can be plated both inside and outside. This gives them more corrosion resistance in demanding applications.

Additional finishes such as black oxide, mechanical zinc plating, cadmium plating, and phosphate and oil coatings further enhance corrosion resistance and longevity.

Unique Customizations

Slotted pins can be manufactured with unique features, including flared or headed pins, circumferential bevels with slot edges or wave tips below the surrounding diameter, specially closed gaps, and designs created specifically for use in automatic feeds.

The Most Versatile Fastener On The Market

Slotted tension pins are an industry-standard fastener, offering strength, flexibility, and cost efficiency across countless applications. Their self-locking design, easy installation, and ability to replace multiple fasteners make them a preferred choice for manufacturers seeking reliability and performance. Whether you are looking to optimize your fastening solutions or explore custom configurations, slotted pins can offer unique advantages.

For over 50 years, Vogelsang Fastener Solutions has been a trusted name in the fastening industry. As a leading manufacturer of slotted tension pins, Vogelsang has continually innovated to meet the evolving needs of engineers and manufacturers.

It has thousands of standard products in stock and ready to ship, with the largest selection of metric slotted pins, with pins ranging from M1 to M50 outer diameter, all the way up to 250mm in length. Large diameter pins are available up to M50 (metric) and up to 7 inches long.

These thru-hardened fasteners are an extremely cost-effective option and can be designed to fulfill the most demanding applications. You’ll be impressed by how these fasteners simplify product design, increase product reliability, and reduce production costs and rejection losses.

Discover how slotted tension pins can enhance your applications. Request samples, consult with our engineering team, or explore our product range today!