Grommets

What are grommets?

Grommets are rubber rings that fit into holes in panels, enclosures, frames, and machine guards to protect cables, wires, hoses, and pipes that pass through them. The edges of a drilled or punched hole in metal can be sharp, and vibration and movement can quickly cause a cable or hose to rub against the edge, wearing through its outer cover. A grommet lines the hole with a soft, flexible rubber edge, preventing chafing and damage while giving a neat, professional finish.

Grommets also help seal the hole against dust, dirt, and moisture, reduce rattling and vibration, and can be used to blank off unused holes.

A typical rubber grommet has:

• Inside diameter - the hole through the centre, where the cable, wire, or hose passes through
• Outside diameter - the overall size of the grommet’s outer flanges
• Groove - a channel around the outside of the grommet that sits in the panel hole and holds the grommet in place
• Thickness - the overall depth of the grommet from one face to the other

Grommet sizes are usually given as a combination of these dimensions, such as inside diameter × outside diameter × thickness. For example, a 17 × 28 × 8 mm grommet has a 17 mm inside diameter, a 28 mm outside diameter, and an 8 mm overall thickness.

Key features:

• Protects cables and hoses - stops sharp hole edges cutting or wearing through insulation and hose covers
• Seals holes - helps keep out dust, dirt, and moisture
• Reduces vibration and noise - cushions cables and pipes, reducing rattling
• Neat finish - gives holes a clean, professional appearance
• Easy to fit - pushes into place by hand, with no tools needed
• Oil resistant options - nitrile rubber grommets resist oils, greases, and fuels
• Range of sizes - available individually or in assorted kits covering many hole and cable sizes

In simple terms, a grommet is a small rubber ring that protects cables and hoses where they pass through holes, keeping them safe from damage and sealing the gap.

Why are grommets essential?

Grommets are essential because cables and hoses that rub against bare metal edges can fail. Over time, vibration and movement can wear through cable insulation, causing short circuits, electrical faults, or even fire risks, and can damage hoses, leading to leaks. Grommets prevent this damage simply and cheaply, while also helping to seal enclosures and keep equipment tidy.

Their main benefits are:

• Prevents chafing - protects cable insulation and hose covers from sharp edges
• Improves electrical safety - reduces the risk of damaged insulation, short circuits, and electrical faults
• Prevents leaks - protects hoses and pipes from wear where they pass through panels
• Helps seal enclosures - reduces the entry of dust, dirt, and moisture
• Reduces vibration and noise - cushions cables and pipes, stopping rattles
• Tidy installation - gives a clean, finished look to panels and enclosures
• Blanks off unused holes - closed or blind grommets can seal holes that are no longer needed
• Low cost - a simple, inexpensive way to protect valuable cables, hoses, and equipment

Grommets are used across a wide range of industries and applications, including:

• Electrical enclosures and control panels - protecting cables entering cabinets and boxes
• Automotive and vehicles - protecting wiring and pipes passing through bulkheads, panels, and chassis
• Agricultural machinery - protecting cables and hoses on tractors and implements
• Industrial machinery - protecting wiring and pipes through frames and guards
• Hydraulic and pneumatic systems - protecting hoses and pipes passing through panels
• Marine - protecting cables and pipes through bulkheads and panels
• Appliances and electronics - protecting cables entering cases and housings
• Furniture and DIY - neat cable routing through desks, panels, and cabinets

The main types of grommets

Grommets are usually grouped by their design and material.

By design:

• Open grommets - the standard type with an open centre, allowing cables, wires, and hoses to pass through
• Blind or blanking grommets - have a closed centre, used to seal unused holes
• Membrane grommets - have a thin centre that can be pierced or cut to suit the cable, giving a tight seal
• Split grommets - have a cut through one side, allowing them to be fitted around cables that are already installed
• Wiring grommets - designed to protect wires and cables in vehicles, panels, and enclosures

By material:

• Nitrile rubber grommets - resist oils, greases, and fuels, making them ideal for machinery, vehicles, and hydraulic applications
• Natural rubber grommets - flexible and economical, suited to general use where oil resistance is not required
• EPDM rubber grommets - resist weather, ozone, and UV, making them suitable for outdoor applications
• PVC grommets - economical and suitable for general electrical and light-duty use
• Silicone grommets - handle high and low temperatures, used in demanding environments

Assorted kits:

• Assorted grommet kits - contain a range of popular grommet sizes in a compartmented case. They are ideal for workshops, maintenance teams, electricians, and vehicle repairs, as they make it easy to find the right size for any hole and cable

How to choose the right grommets?

Choosing the right grommet means matching it to the hole, the panel, and the cable or hose passing through it. Work through these points in order:

• Panel hole size - measure the diameter of the hole in the panel. The grommet’s groove should match this size so it fits snugly
• Panel thickness - check the thickness of the panel. The width of the grommet’s groove should suit the panel so the grommet stays securely in place
• Cable or hose size - choose an inside diameter that fits the cable or hose, with a snug fit for sealing or a little clearance if the cable needs to move
• Outside diameter - make sure the outer flanges are large enough to cover the edge of the hole and fit the available space
• Design - choose an open grommet for cables and hoses, a blanking grommet for unused holes, a membrane grommet for a tight seal, or a split grommet for cables already fitted
• Material - choose nitrile rubber for oil, grease, and fuel resistance, EPDM for outdoor and weather resistance, silicone for extreme temperatures, or natural rubber for general use
• Environment - consider temperature, moisture, oil, chemicals, and sunlight
• Quantity and range - consider an assorted kit if you need a variety of sizes for different jobs
• Quality and brand - choose grommets from reputable suppliers for consistent sizing and durable rubber

FAQ - All you need to know about grommets

What is a grommet used for?

A grommet lines a hole in a panel or enclosure to protect cables, wires, and hoses from sharp edges. It also helps seal the hole, reduce vibration, and give a neat finish.

What do the sizes on a grommet mean?

Grommet sizes are usually given as inside diameter × outside diameter × thickness. For example, a 17 × 28 × 8 mm grommet has a 17 mm inside diameter, a 28 mm outside diameter, and an 8 mm overall thickness.

How do I measure for a grommet?

Measure the diameter of the hole in the panel, the thickness of the panel, and the outside diameter of the cable or hose. Choose a grommet with a groove that fits the hole and panel, and an inside diameter that fits the cable or hose.

What is nitrile rubber?

Nitrile is a synthetic rubber with good resistance to oils, greases, and fuels. This makes nitrile grommets ideal for machinery, vehicles, and hydraulic applications.

How do I fit a grommet?

Make sure the hole is clean and free of burrs. Fold or squeeze the grommet slightly, push one side of the groove into the hole, then work the rest of the grommet into place around the edge. A little soapy water can help it slide in more easily.

Can I fit a grommet around a cable that is already installed?

Yes, if you use a split grommet, which has a cut through one side so it can be opened and fitted around the cable.

What is a blanking grommet?

A blanking grommet has a closed centre and is used to seal holes that are not being used, keeping out dust, dirt, and moisture.

Do grommets make a waterproof seal?

Grommets help reduce the entry of dust and moisture, but a standard grommet is not always fully waterproof. For a fully sealed cable entry, consider membrane grommets or cable glands designed for the required level of protection.

Why should I buy an assorted grommet kit?

An assorted kit gives you a range of popular sizes in one organised case, so you always have the right grommet on hand for different holes, cables, and hoses.

How do I know when a grommet needs replacing?

Replace grommets that are cracked, hardened, split, missing, or no longer holding firmly in the hole, as they may no longer protect the cable or hose properly.