Tapered plugs vs parallel plugs
Both types of plugs offer protection, yet both are uniquely different. In this guide, we’ll cut through the confusion to help you understand their differences – along with their similarities. You’ll learn when to choose each type so that you can protect your application. Here, we’ll cover:
- What is a tapered plug?
- What is a parallel plug?
- What are the differences?
- Applications of tapered and parallel plugs
- Materials
- Industries
What is a tapered plug?
A tapered plug, as the name implies, has a tapered design which can be pushed into a hole to fill it. Due to the taper, it will work to plug multiple hole dimensions. This typically works well on machined holes, where tolerances may fluctuate slightly from run to run. Its unique taper style means the plug can be flipped over to become a cap to cover a tube or stud. When used as a cap it will also work to cap multiple tube or stud dimensions.
While this example lacks a flange, other tapered plugs have them. Flanges provide a:
● Gripping surface, making it easy to insert and remove the plug by hand.
● Tight seal for better protection against ingress.
● Stability, preventing the plug from pushing too far into the hole.
What is a parallel plug?
These are also called straight-wall plugs and parallel protection plugs and are pushed in to fill holes. The parallel plug is straight walled, giving it more grip across its full plug portion into the mating hole than a tapered plug. Its straight walls means it only fits into one hole diameter. The primary function of parallel plugs is to protect the hole, and thus the application, from dust, debris, moisture or damage. They typically have a flange – as shown on the right – which is a wider rim on one end of the plug.
What are the differences?
Let’s break down the key differences between tapered and parallel plugs.
Shape:
● Parallel plugs: Cylindrical shape with a consistent diameter throughout the length.
● Tapered plugs: Its conical shape makes it ideal for creating a secure fit for sealing tapered threads.
Function:
● Parallel plugs: Their main purpose is to plug a hole and protect against dust, debris, or minor damage.
● Tapered plugs: Due to their conical shape, they can create a tighter seal within a hole that varies slightly in size. This makes them suitable for applications where a snug fit is important, such as masking during painting or protecting threaded components.
Sealing:
● Parallel plugs: They rely on the flange (wider disc on one end) to create a snug fit.
● Tapered plugs: The tapered design itself helps create a tighter seal within the hole.
Dual Use:
● Parallel plugs: These are exactly what the name says: plugs. They’re designed to fit internal threads or holes.
● Tapered plugs: By flipping the tapered plug upside down, the wider base can be placed over an application’s component for protection, creating covered tapered caps.
If you’re looking to protect threads, you’ll find it helpful to read our expert Guide to Thread Protection Caps and Plugs.
Applications of tapered and parallel plugs
We’ve mentioned that tapered plugs can act as tapered caps. Let’s look at those, along with other types of tapered and parallel plugs. For further help, our experts have also put together the Ultimate Guide to Caps and Plugs.
Wide-flange tapered plugs
An example of wide-flange tapered caps and plugs. Plugs and available with even wider flanges. They offer superior protection for threaded and non-threaded pipes, ports, and access points during storage and transportation. They protect against damage, dirt, moisture, debris, and even corrosion. A unique feature of these wide-flange tapered caps and plugs is their versatility – the tapered design allows them to fit a range of inside or outside diameters, ensuring a secure fit for various applications.
The wider flange provides additional support for the contact surface, preventing accidental pushing in of the plug. Made of LDPE.
● Wide-flange tapered plugs and caps are ideal for applications where stability is crucial:
○ Hydraulic systems
○ Automotive components
○ Demanding chemical or medical industries
Heavy-duty caps and plugs
With a robust design, this features a thick wall and a tapered sealing ring, protecting critical components against damage from dust, debris, and even impacts. Installation is easy if used as a cap or plug, with a convenient push-fit design.
They offer exceptional durability and resist impact, abrasion, and harsh conditions. Made of LDPE. Also available in standard caps and plugs.
● Ideal for applications in:
○ Machinery
○ Automotive
○ Industrial settings
High-temperature Tapered Plugs
These reusable tapered plugs come in two materials, premium silicone and cost-effective EPDM. Both materials provide a secure fit, but selecting the right one depends on your specific application's temperature requirements.
For larger diameter holes, the hollow tapered plugs offer an economical solution. The hollow core allows for compression, creating a tighter seal. Silicone tapered plugs are the premium option, boasting a high-temperature rating of 600°F (316°C) ideal for demanding environments. These silicone plugs are also reusable and come in a variety of colours for easy identification.
Black EPDM tapered plugs offer a cost-effective alternative with a slightly lower heat resistance of 218°C. However, EPDM excels in applications requiring superior chemical resistance. By considering both temperature and chemical exposure, you can choose the most suitable material for your high-temp masking needs.
● Designed for:
○ Masking applications
Covered Tapered Plugs
Covered tapered plugs offer a reliable and reusable solution for plugging holes. Their unique design features convex sides, creating a secure fit that effectively guards against ingress and potential damage. The convenient push-fit design makes installation and removal easy. Made of silicone.
● These versatile plugs can be used for:
● Sealing blind holes and pipes
● Protecting furniture
● Protecting electrical boxes
Parallel Protection Plugs
Push-fit parallel plugs are for protecting holes from ingress. Available in:
● Thermoplastic rubber (TPR) for resistance to acid
● PVC, for resistance to shredding and ideal for threaded applications
● Green Vinyl, which resists oils and greases
● Designed for: Masking applications
Parallel Protection Plugs with Small Flange
This general-purpose parallel plug protects against dirt and corrosion. Ideal for storage and transport applications, it keeps components safe from external contaminants. The handy flange design allows for easy removal by hand, even from snug fits. Made of LDPE.
● Designed for: General protection
Materials: at a glance
We’ve put together this helpful summary of common materials often used for parallel and tapered plugs.
|
Material |
Characteristics |
Ideal Applications |
Examples |
| LDPE | Affordable, versatile, basic protection against dust, dirt, moisture | General-purpose protection, storage, transport | Wide-flange tapered plugs, parallel protection plugs |
| Silicone | High-temperature resistance, reusable | Demanding environments, masking during high-temperature processes, repeated plugging/unplugging | High-temperature tapered plugs, covered tapered plugs |
| EPDM | Cost-effective masking alternative to silicone, excellent chemical resistance | Industrial settings, applications with chemical exposure | High-temperature tapered plugs |
| TPR | Acid resistance | Masking | Parallel protection plugs |
| PVC | Resistance to shredding | Masking | Parallel protection plugs |
| Vinyl | Oil and grease resistance | Masking | Parallel protection plugs |
Industries
We’ve shown you applications, which tells you the industries that use tapered plus and parallel plugs. Below is a summary of the various industries that reply on these components.
|
Industry |
Tapered Plugs |
Parallel Protection Plugs |
|
Manufacturing |
– Masking during processes (high-temp silicone/EPDM) – Protecting threaded components – Sealing pipes/tubes |
– General protection (storage, transport) – Masking – Protecting threaded components (PVC) |
|
Automotive |
– Protecting components during assembly (silicone/EPDM) – Sealing ports/access points |
|
|
Chemical & Medical |
– High-chemical resistance (EPDM) |
|
|
Construction |
– Sealing pipes/conduits (temporary closure) |
|
|
Furniture & Appliances |
|
– Plugging unused holes |
Try before you buy
Request free samples now to make sure you’ve chosen exactly what you need. If you have any questions about tapered or parallel plugs, our experts are always happy to advise you.
Our experts have also provided help in our guide, How to Choose Caps and Plugs.
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 528 0474.