Key Questions to Ask When Ordering Rubber Grommet

What is a rubber grommet?

These are tubes, or edging, used to cover the rough and sharp edges of a panel hole. Rubber grommets grip wires and cables that pass through the hole, keeping them secure while protecting them from abrasions, cuts and snags. At the same time, they also protect wires and cables from liquid and dust ingress.

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In this article we cover:

Rubber grommet materials
What are IP ratings?
Types of rubber grommets and their uses
Different rubber materials and industries
Shapes of rubber grommets
How to measure rubber grommet size

They're used in almost every industry and application, ranging from vehicle rubber grommets to grommets for back boxes. Those industries include:

• Electronics
• Automotive
• Aircraft design
• Construction
• Data centers
• Telecommunications
• Medical equipment
• Office furniture

Rubber grommets are also ideal for reducing vibration, which makes them especially useful to the automotive and electronic industries. If cables are involved, there's a good chance you'll find this critical cable management solution.

At Essentra, we have a range of rubber grommets available.

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Rubber grommet materials

Before we look at types, we should talk about materials, which can dictate what the grommet should be used for.

'Rubber grommets' also refer to those made of synthetic rubbers. The most commonly used materials include neoprene grommets, nitrile rubber grommets and silicone grommets.

There are four other materials you should know about are:

• Ethylene propylene diene monomer (EPDM)
• Thermoplastic elastomer (TPE)
• Thermoplastic vulcanizate (TPV)
• Styrene butadiene rubber (SBR)

EPDM: The next-generation of ethylene-propylene rubber. It provides excellent electrical insulation and resists weathering, which makes it ideal for sealing purposes. It's also why this synthetic rubber is an outstanding material for grommets. Learn more about this material in our guide, What is EPDM rubber?

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TPE: Designers are also opting for TPE for the cost savings while still getting the rubber-like characteristics they're after. TPE offers good electrical properties and excellent resistance to flexural fatigue, chemicals and weathering.

TPV: This is a type of TPE and also called TPE-V. Its characteristics are more similar to EPDM, making it an excellent choice for sealing applications. It's especially popular with the automotive industry for under-the-hood applications ' for example, as a radiator rubber grommet ' and where heat resistance and the ability to perform in oily environments is necessary.

SBR: is a cost-effective choice that's very similar to nitrile rubber, with nitrile being a bit softer. SBR is primarily used in applications where hoses, gaskets, belts and seals are required.

Shapes of rubber grommets

Round rubber grommets are the most common shape. Along with oval rubber grommets, also called oblong rubber grommets, they're used in automotive, electrical enclosures ' generally, for any panel in any industry.

Square rubber grommets and rectangular rubber grommets tend to feature on office furniture, such as computer desks. Here again, round grommets are common for furniture applications. For example, round rubber grommets for glass table tops are common. Finally, D-shaped rubber grommets are mostly used in machinery, computers and as automotive spare parts.

How to measure rubber grommet size

This is straightforward: measure the panel. You'll need to know panel thickness and the size of the hole that the grommet will fill.

Rubber grommets come in different sizes and thicknesses. You can find a 1/2" rubber grommet and 3/4" rubber grommet. They go up to a 4" rubber grommet and 6" rubber grommet and beyond. Once you have the measurements of the hole you need your grommet for, look at the manufacturer's grommet sizes.

The example below shows you how Essentra Components displays the information for you. This is for a standard rubber grommet. You can see the important information you need at a glance, from compatible hole diameter ' meaning what hole the grommet will fit ' to the panel thickness.

In these situations, I use bulkhead fittings. It saves the annoyance to getting this stuff to seal properly, any slight leverage and there's now a leak. These are available in several sizes at most plumbing supply stores. If there's a gentle curve to the surface this has to penetrate, I've used a large O-ring instead of the supplied gasket. They're available as glue type fittings, or internally threaded.

Schedule 40 3/4" PVC pipe has a nominal diameter of 1.050 inches. The grommet you have highlighted has a 1/2" bore or inside diameter. A grommet with a one inch bore should provide a tight seal. Just remember that water tightness also relys on a tight seal between the grommet and the container. This requires a hole as close to the shoulder diameter (not the overall diameter) as possible. As this type of container has a thin wall I would install the grommet with a generous amount of silicone sealer.

I actually just built something similar. I tried all different types of gaskets, washers, etc. and all of them leaked under the pressure. I finally settled on a large metal washer on either side with a nut to apply pressure and liberal amounts of silicone. It's been a week so far and no leaks. The other trick is to drill the holes slightly smaller than needed. I then heated up the plastic to make it pliable and pushed the pipe through. It's helped make a nice tight seal, along with the silicone.

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