What are Shelf Bevels?
On our Online Order page, we offer a "Shelf Bevel" option, but unless you're familiar with the different bevel options, it may be confusing to know what exactly a shelf bevel is.
This article will illustrate the difference between shelf and V bevels and how to determine if the frame you have has either of these popular bevel types.
Most Common Bevel - The "V" Bevel
The Shelf Bevel
The shelf bevel (sometimes referred to as a step bevel), is usually found in sunglasses that curve around the face. There are several advantages for using a shelf bevel instead of a v-bevel, with the main advantage being that it helps to keep the lens secured in the frame.
Due to the higher than usual curve in many styles of sunglasses (some safety glasses, etc.), regular beveled lenses will be more likely to pop out the frame (especially the top or bottom).
Some frames will actually require a shelf bevel because the back of the frame window is made higher than the front (as seen in the picture below).
A regular "V" style of bevel won't fit in this style of frame correctly, and it will be "pushed" out by the higher ledge. Many novice Opticians will make the mistake of trying to edge lenses for this style of frame using the "V" bevel and will keep re-edging the lenses to a smaller and smaller size; not because they're too big, but because the back edge of the frame just won't allow the hide-a-bevel (another name for the "V" bevel) to seat correctly in the frame.
To summarize, a shelf bevel is a special type of bevel found on many highly curved sunglasses and some safety frames. By trimming extra material from the lens edge leaving a "shelf" around the perimeter, it makes it easier to snap securely into the frame and help prevent it from popping out.
Still not sure if a frame has a shelf bevel or not? Usually it's found in curved sunglasses (like the picture at the top of this article); but to determine for sure, simply remove one of the lenses and inspect the bevel type the lens has. An even more accurate method (Note: some demo lenses are made thin already so they don't have to have a shelf bevel, but lenses with prescriptions will usually be thicker and will thus require a shelf bevel for the best fit), look at the inside of the actual frame window.
If the back of the frame window is significantly higher than the front, it will likely require a shelf bevel to properly fit prescription lenses into the frame.
The picture below shows a side-by-side comparison of the difference between a regular v bevel lens (on the left) and one with a shelf bevel (pictured on the right).