A guide to indexing plungers
Let’s talk about those small, but crucial, components that help precisely position and secure parts within machinery. Indexing plungers are versatile mechanical elements that play a vital role in ensuring accurate and repeatable positioning across various applications. From assembly jigs to intricate automation setups, indexing plungers offer a reliable and efficient solution for countless industrial needs. This comprehensive guide dives into indexing plungers, covering:
What are index plungers?
Types of indexing plungers
Materials
Applications of indexing plungers
How our indexing plungers can help with electronics and automation
What are index plungers?
Index plungers, also known as indexing plungers or indexing pins, are mechanical components used in machinery to precisely locate and secure parts in a specific position. They’re often used in applications that require repeated, consistent positioning, like assembly jigs, machinery setups, and adjustable fixtures.
Key components and functions of index plungers
● Positioning and locking: Index plungers incorporate a plunger pin designed to lock and unlock components into designated positions. This mechanism ensures precise placement and stability.
● Retractable pin design: The indexing plunger pin is typically retractable, often using a spring-loaded system. This allows for effortless movement between locked and unlocked states.
● User-friendly operation: Some index plungers feature ergonomic handles or levers for convenient manual operation. However, some models may require tools for activation, depending on the specific application and design.
● Robust construction: To withstand demanding industrial environments, index plungers are typically constructed from durable materials like stainless steel or specialised alloys. This ensures longevity and reliability.
View our range of indexing plungers
Types of indexing plungers
These components serve multiple applications, from gym and medical equipment to conveyor systems and machine fixtures. Our plungers come in various metric thread sizes to suit your specific project needs.
Cam-action indexing plungers
These lever indexing plungers feature a unique cam-shaped body design. To retract and lock the plunger pin, simply rotate the lever 180 degrees. Reversing the lever rotation releases the lock, and a spring mechanism instantly returns the pin to its extended position.
Cam-action indexing plungers are built for heavy-duty applications, with robust construction and large levers that can be easily manipulated, even while wearing gloves. Our cam index plungers are available in either stainless steel or burnished steel.
Non locking and locking index plungers
Non-locking threaded index plungers enable fast adjustments on a range of platforms, fixtures, and tables. They automatically spring back into the engaged (extended) position when released, meaning the pin immediately re-engages with the part or surface. The non-locking type is best used for fixed positioning, when infrequent retraction is needed.
Locking index plungers can be pulled back and locked in the retracted position, allowing for free movement until the user releases and re-engage them. Locking index plungers are ideal in situations where parts or components need frequent repositioning or adjustments, as they provide the option to keep the plunger disengaged. Available in stainless steel, burnished steel, steel, and aluminium with nylon knobs.
Flanged indexing plungers
Plate-mount indexing plunger with countersunk screw holes are ideal for securing into thin, flat surfaces like panels or enclosures. These versatile plungers are widely used for locating, positioning, indexing, and securing components, enabling fast adjustments on various platforms, fixtures, and tables. Indexing plungers with pull knob available in steel or stainless steel. Nylon knobs.
Press-fit plungers
These compact, spring-loaded devices are commonly used as detents, enabling easy push-on and push-off actions. As a type of spring plunger, they also serve as ejectors in manufacturing settings. Applications include positioning and locating workpieces, functioning as rollers in conveyor systems, and acting as latches to secure panels and covers in electrical equipment. Available in type 1: stainless steel housing and ball – AISI 305/20c. Also, type 2: plastic housing and stainless steel ball.
Indexing plungers often pair well with industrial pins. While indexing plungers offer adjustable positioning and secure latching for components that need to be frequently repositioned or locked in place, industrial pins provide more permanent alignment, reinforcement, and shear force resistance.
Our experts help you learn more in A guide to industrial fastener pins.
You might also prefer using spring plungers, which exert consistent force to position or hold components in place. This spring plunger combines reliable performance, secure latching, and simplicity of use. It includes a pull ring for easy hand retraction, allowing for convenient lifting of the plunger, making it ideal for tasks like locating, positioning, and securing. Typical applications include gym equipment, such as weight machines. This ring pull design offers a straightforward, cost-effective alternative to a knob-style plunger. Available in nickel-plated housing and a stainless steel indexing plunger pin.
View our range of spring plungers – pull ring/hand retractable
Materials
Steel, stainless steel, aluminium, and burnished steel are common materials used to manufacture indexing plungers. If you’re not familiar with burnished steel, this is a process that creates a thin, black protective layer on its surface, enhancing both corrosion resistance and visual appeal. This process typically involves immersing the steel in a boiling alkaline oxidising salt solution, which results in the formation of an iron oxide layer.
The table below summarises the key characteristics of each material to help you choose the right indexing plungers for you.
| Characteristic | Steel | Stainless steel | Burnished steel | Aluminium |
|---|---|---|---|---|
| Composition | Primarily iron with small amounts of carbon | Iron, carbon, chromium (10.5%+), and other alloying elements | Base steel (usually carbon steel) with a polished finish | Primarily aluminium with trace elements like copper, magnesium, and silicon |
| Corrosion resistance | Low; prone to rust | High; chromium provides resistance to rust and corrosion |
Moderate; burnishing adds some resistance but not as durable as stainless | High; forms a natural oxide layer that resists corrosion |
| Finish | Matte or dull finish | Typically shiny or polished | Glossy, reflective, smooth finish | Matte to glossy, often anodized for colour or protection |
| Durability | High; can be hardened and tempered | Very high; especially suited for harsh or corrosive environments | High but finish can be scratched or wear over time | Moderate; softer and less wear-resistant than steel but highly durable in non-abrasive environments |
| Weight | Heavy, dense | Heavy, dense | Heavy, dense | Lightweight; one-third the density of steel, making it easier to handle and install |
| Maintenance | Regular rust prevention needed | Heavy, dense | Requires occasional re-polishing to maintain shine | Low; resistant to rust but may require occasional cleaning for oxidation spots |
Applications of indexing plungers
We’ve put together this table to give you an overview of each plunger type’s primary applications and typical industries. Use it as a handy guide to identifying the right indexing plunger for your specific operational needs.
| Indexing plunger | Primary applications | Industries |
|---|---|---|
| Cam action | Heavy-duty locking and positioning, quick-release engagement/disengagement for large machinery and equipment | Industrial manufacturing, construction, heavy machinery |
| Non-locking | Fixed positioning; ideal where minimal retraction is needed (e.g., machinery stops, fixture positioning) | Production lines, machinery adjustments, manufacturing |
| Locking | Frequent repositioning; adjustable setups where plunger can lock in the retracted position. Ex: making adjustments in automotive seats, tables, jigs | Automotive, assembly lines, flexible workstations, lab equipment |
| Flanged | Mounting on thin surfaces (e.g., panels and enclosures), securing and positioning components | Electrical/electronic housings, assembly stations, control panels |
| Spring plungers – pull ring/hand retractable | Manual, secure latching with easy retraction (e.g., gym equipment, adjustable equipment) | Fitness equipment, light industrial applications, furniture |
| Press fit | Push-on/push-off detents, ejectors for positioning workpieces, securing panels, or conveyor rollers | Manufacturing, material handling, electrical equipment |
How our indexing plungers can help with electronics and automation
Indexing plungers enhance electronics and automation systems by providing reliable positioning, alignment, and securing mechanisms. Here’s how specific types of indexing plungers can help:
1. Non-locking index plungers
Ideal for fixed positioning in control panels, robotic arms, or automated inspection systems. They allow precise alignment of components, such as sensors or camera systems, and ensure stability with minimal retraction needed, which can prevent misalignment in sensitive electronic setups.
2. Locking index plungers
Great for automation systems where components require frequent adjustments, such as adjustable robotic mounts and workstations. Locking index plungers allow these parts to be repositioned as needed and then securely locked in place. This is particularly useful in assembly lines or testing stations, where flexibility and reliability are essential.
3. Flanged indexing plungers
These plungers can be mounted to thin panels or enclosures, making them useful for securing access panels in control systems or electronic housings. They enable quick and easy access to electronic components for repairs, adjustments, or inspections in industrial automation settings.
4. Press-fit plungers
Suitable for detents or positioning components in smaller automated devices. They can act as quick-release mechanisms for secure, push-on/push-off functions, useful for ejecting parts, holding circuit boards in place, or creating temporary latches in modular electronic setups.
5. Spring plungers – pull ring
In applications that need manual retraction of components, such as retracting sensors, testing probes, or electronic fixtures, spring plungers with pull rings provide a straightforward and reliable mechanism. Cost effective for lightweight equipment in automation systems, allowing secure latching and easy hand retraction for adjustments.
If your application involves electronics, you’ll find it helpful to read our expert Guide to PCB standoffs.
If your application is focused on automation, our experts can help you learn more about other components you’ll need: What are automation ball and socket joints?
Download free CADs
Free CADs are available for most solutions, which you can download. If you’re not quite sure which indexing plunger will work best for your application, our experts are always happy to advise you. Whatever your requirements, you can depend on fast dispatch.
Questions?
Email us at sales@essentracomponents.co.uk or speak to one of our experts for further information on the ideal solution for your application 0345 728 0474.