Locking gaskets or window gaskets are lengths of rubber that
lock into place to provide a secure seal between stationary glass and a body
panel. They are either self-locking or have a key. Locking gaskets are used
with the windows and windshields on vehicles and mobile equipment. They’re also
installed around the viewing windows on machine and equipment enclosures.
Choosing the right locking gasket is critical because these
industrial rubber seals hold window glass in place. Gasket fabrication and
installation are also important. Window channels that are too small won’t fit
over the glass. Forcing them into place can cause windows or windshields to
break. Rubber locking gaskets that are too large may leak and won’t provide
effective sealing and insulation.
In this guide from Exonic Polymers, you’ll learn how to
select rubber window trim based on dimensions, tolerances, and materials.
Importantly, you’ll learn some best practices for cutting and installing window
How to Choose a Rubber Locking Gasket
Selecting the right locking gasket starts with a few basic
measurements. First, measure the thickness of the glass that the gasket needs
to cover. Next, measure the height and width of this glass. Add these numbers
together and then multiply the sum by two. This gives you the overall length of
the locking gasket that you’ll need.
Some engineers are more familiar with metal parts than with
rubber profiles. That’s why it’s important to understand that rubber can shrink
and stretch significantly. Tight tolerances are possible with metal channels,
but not with the rubber extrusions used in window gaskets. When you define your
seal design then, remember to specify tolerances that are achievable.
You’ll also need the right rubber compound for your
application. With construction and forestry equipment, EPDM is a good choice
because this elastomer remains flexible at low temperatures and resists
moisture and sunlight. With machine and equipment enclosures, locking gaskets
that resist contact with oils may be required. With food processing and medical
equipment, locking gaskets made of FDA-approved rubber may be required.
How to Install a Rubber Locking Gasket
Window gaskets come in lengths of rubber that you can cut
yourself. You can also buy locking gaskets that are cut-to-size and arrive
ready-to-install. Cutting your own window rubber may seem cost-effective, but
mis-cuts create material waste. Plus, the rubber that’s used in locking gaskets
will experience shrinkage. To prevent the edges from separating, you need
extrusions with a bit of extra length.
Before installing the glass, lubricate the locking gasket
with a mixture of soap and water or a silicone-based spray. To prevent the
lubricant from wetting other surfaces, hold the spray bottle or can in one hand
and a piece of cardboard in other. Position the cardboard on the other side of
the window or windshield area that you plan to spray.
To install the glass, start with the body side first. In
other words, don’t start inside the cabin or enclosure. Rest the bottom of the
glass in the gasket so that you don’t have to struggle with the weight of the
window or windshield. A knife-like tool with a plastic blade can help to
prevent glass breakage as you work the gasket’s lip over and around the glass.
When lip is fully over the glass, the glass will pop into place.
Locking Gasket Tool Tips
Next, lock the gasket into itself. Some installers use a
screwdriver, but the blade can slip and scratch the body panel. Gasket tools
with a screwdriver-like handle and hooked end are a better choice. Some have
pointed tip or metal ball at the end. The latter type is effective because the
ball tends to stay in place and won’t rip the gasket. Plus, if the tool comes
loose, the ball is less likely to scratch the body panel.
When you press a locking gasket onto a body panel, remember
to push the gasket’s ends together so that there’s more material in the loop
that forms. Pressing this loop downward forces material into the application
and prevents stretching. If there’s residual lubricant on the window or
windshield, wipe the surface clean with a rag.