This Window Gasket Guide explains what you need to know about window channels for mass transit, heavy equipment, and machine enclosures. Elasto Proxy supplies sealing solutions to manufacturers and repair organizations.

Window gaskets are industrial rubber products that seal the gaps between stationary windows and window frames. They have a smooth surface finish and are extruded into profiles, or channels, with a specific cross-section and dimensions.

  • Engineers choose the window rubber, or elastomer, based on the application environment.
  • Assemblers install window gaskets or window channels as they are sometimes called, along the edges of windshields in heavy equipment, with stationary windows on buses or trains, or with the viewing windows on machine enclosures.
Important: This category of industrial rubber products does not include the flocked gaskets that are used with the moveable windows on cars and trucks. (When a gasket is flocked, it’s coated with textile fibers. Window channels are smooth instead.) 
cab door seals | Thermal Expansion Heavy Equipment Gaskets
Window channels are used with windows that do not open or close, such as on this train.

What are the different types of window gaskets?

There are five main types of window gaskets for stationary windows.

What are window gaskets made of?

Window gaskets are usually made of EPDM, TPEs, or silicone rubber.

  • EPDM is a cost-effective rubber that can withstand outdoor conditions. Often, EPDM window gaskets are used with heavy equipment.
  • TPEs, or thermoplastic elastomers, are used in many of the same applications as EPDM. TPEs are more expensive, but they are recyclable and support custom color matching.
  • Silicone gaskets are used in food processing, medical, or other sanitary applications. Window seals made of FDA approved silicones are available.

To avoid gasket failure, always consider the environment when selecting rubber materials. Use MTAP as your guide.

MTAP | type of rubber
MTAP is an Elasto Proxy acronym that helps guide sealing selection

What is the hardness of window rubber?

The durometer, or hardness of window rubber, is usually between 60 and 70 (Shore A). These gaskets need to be hard enough to withstand the contact pressure that’s exerted upon them, but softer enough to fill the gaps between mating surfaces. 

Why does rubber have different part tolerances than metal?

Rubber has many useful properties, but it can’t match the tight tolerances associated with metal. That’s because rubber is more sensitive to how heat and cold cause materials to expand and contract. The type of tooling that’s used to extrude rubber also affects part tolerances.

Where can you find rubber part tolerances?

Consult the RMA Handbook, a resource with dimensional tolerances for extruded rubber products, for achievable part dimensions. Remember, however, that higher precision comes with higher costs. If you’re used to working with sheet metal or metal profiles, you might need to adjust the tolerances on your drawings.

Are there different tolerances for cut lengths of rubber?

Yes. If you buy cut lengths, remember to account for the cut length tolerances you’ll find in the RMA Handbook. If you’re buying coils of rubber instead, order enough material for all of the windows that you need to seal and account for material waste from miscuts. (Better yet, consider outsourcing your gasket fabrication. In-house cutting could more expensive than you think.)

Extruded Rubber Tolerances | Rubber Part Tolerances | tolérances sur des pièces en caoutchouc
Rubber part tolerances are not the same as metal part tolerances

How does window glass thickness affect seal selection?

Measure the thickness of the window glass to determine the size of the edge that your window gasket needs to grasp and hold. There must be enough room for the glass to fit inside the gasket, but not so much room that the glass will rattle or fall out.

Are there standard and custom window channels available?

Elasto Proxy supplies standard window channels for glass edges with the following thicknesses:

  • 1/8 in. (175 mm)
  • 3/16 in. (4.7625 mm)
  • 1/4 in. (35 mm)
  • 3/8 in. (9.525 mm)
  • 1/2 in. (7 mm)

You can also order custom window channels with special edge dimensions.

How do you calculate window glass length and gasket length?

To determine the window glass length (WL), multiply the height (H) and width (W) of the glass.

H x W = WL

To determine the gasket length (GL),  multiply WL by two.

WL x 2 = GL

window channels
This infographic provides window channel information at-a-glance.

How do you install a window gasket?

First, push the ends together and leave the extra material in the loop that forms. During gasket installation, workers may find that there’s some extra rubber for each window. That’s by design since all rubber gaskets experience some shrinkage over time.

Next, press down the loop so that you force more material into the gap. This keeps the gasket from becoming over-stretched.

Then, spray the gasket with a silicone-based lubricant or soap and water. Now use a hand tool to unlock it so that it’s ready for installation. Install the glass on the body size first, resting the bottom of the glass in the locking gasket.

Next, use a plastic installation tool as you work the gasket’s lip over and around the glass. Finally, use a hand tool to lock the gasket back into itself.

Do window gaskets lock into place?

Some lock in place. Others have a self-locking mechanism.

  • Locking gaskets are two-piece products that lock into position with a lock strip or key.
  • Self-locking channels are one-piece seals that do not require these attachment mechanisms.

Who supplies window gaskets and can help with installation?

Elasto Proxy distributes window rubber and supplies cut lengths using our water jet cutting equipment. For over 30 years, we’ve been providing industries like mobile equipment and enclosures with the sealing and insulation solutions that they need.

To request a quote or for more information, contact us.   

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