Eyeglass frames have several components and the names of the different frame parts are useful to learn. Eyeglass frames have two basic parts: the frame front that holds the lenses, and the temples that hold the frame from falling off your face.
The frame front is composed of two eyepieces connected by the bridge. The eyepieces hold the lenses and connect to the temples by hinges, and the bridge is the part over your nose. Usually, there is just one piece of material connecting the two eyepieces, called a single bridge construction. Some, especially larger, frames have a double-bridge for extra support, with two pieces of material connecting the two eyepieces.
The eyepieces on a full-frame completely encircle the lens. On metal frames, the eyepiece is held together with a screw that is removed when the lenses are installed, and then replaced. On plastic eyeglasses frames, the eyepiece is heated until it expands, the lens is snapped into position, the frame cools and contracts snugly around the lens. On half-rimless frames, the lens in held in place by a nylon cord called the eyewire that attaches to the frame in two places. The rim of a pair of eyeglasses is the part of the eyeglasses frames eyepiece that holds the lens in place. The rim can completely encircle a lens in the case of full frames, or partially hold the frame in the case of semi-rimless frames, or there can be no rim at all in the case of rimless frames.
On the outer edge of each eyepiece some material extends out beyond the shape of the lens. This is called the endpiece, and connected to it is the hinge which holds the temples to the frame front. Endpieces can be designed larger so that a larger person can wear a somewhat smaller lens without the frame pinching the sides of the head.
Many eyeglasses frames, most commonly metal frames, have nosepads attached to the inside of the bridge. Nosepads are normally made of a plastic or silicone materials, and aid in the comfortable resting of the frame on the wearers nose. Nosepads can be adjusted to accommodate an individuals nasal structure, as well as the proper positioning of the lenses in front of the wearers nose. Nosepads are attached to pad arms, which are welded to the frame front. Nosepad arms are made of a malleable metal so that they can be adjusted (bent) during a fitting. This metal is then welded on to the frame front which could be made of titanium, monel, stainless, or other materials. Occasionally these weld points weaken and the pad arms break off the frame there. Nosepads are attached either by a screw (screw-in nosepads), or they are push-in nosepads which require no screw. Most nosepads are designed this way so that the nosepads can be replaced when they wear out. Pad arms are always made out of malleable metal so they can be adjusted, even on titanium or aluminum frames. Plastic eyeglasses frames, and some metal eyeglasses frames do not have nosepads; they have a saddle bridge construction. This term refers to a style of bridge in which the arched portion of the bridge lies directly on the bridge of the wearers nose. Saddle bridges are more common with plastic frames than with metal frames. Metal frames with saddle bridges do not have nosepads.
There are many different types for frame temples, which connect and hold the frames front to the wearers head behind and below the ears. The most common is the skull temple, with the long straight shaft that is bent with a 45 degree angle at the top of the ear near the end of the temple which is called the temple tip. The shaft is the straight part that extends from the connection point at the eyeglasses frame front to the bend in the temple. Library temples are straight all-shaft temples with no bend in them. Most eyeglasses frames' temples have temple tips that are malleable so that they can be changed (bent) to adjust the fit of the glasses. Frames that are made of titanium, aluminum, and stainless often have a different type of metal welded on to the temple tips. Temple tips are usually coated by a plastic material that is designed to give and adjust to the metal if the metal is bent during an adjustment. These plastic temple tips covers can become worn out and on some frames they are designed to be replaced.
Cable temples refer to curly temple tips, which curl behind your ears. Cable temple hold glasses in place better and are a good choice for people in active situations and for children. However, coable temples are not easy to adjust, and if they pinch your ear it is very difficult to adjust the temples as the metal is not designed to be adjusted easily.
Eyeglasses frames' hinges are used to connect the temples to the front of the eyeglasses frames, while allowing the temple to fold flat against the frame. Most frames use external hinges, which are mounted on the inside of the temple shaft. Internal hinges are buried inside the shaft of the temple, hiding the mechanism from view. Hinges are a small but very important component in the overall quality of your eyeglass frame. If the hinge is not mounted on the frame properly, it will disengage which leads to a very difficult (or impossible) repair job. Low quality hinges with wear out, the screw will pop out and get lost, and they will wear quickly leading to rattling or sloppy action. Good quality hinges have a smooth and consistent action that does not wear over time, with friction that is consistent throughout the entire range of motion. We still find that the best quality hinges are made in Germany. You can find these in European and Chinese frame, and in most better quality frames. Unfortunately, it is very difficult to find out from the manufacturers which hinges they use in a particular frame.
A spring hinge is a hinge that is mounted on the temple shaft and allows for spring action. Spring action hinges can bend beyond the limit of normal hinges, which can limit breakage of the frame under stress. Spring action hinges also help to keep frames properly aligned. Spring hinges are found on both external and internal hinges.
Hingeless eyeglasses frames use a very springy material, usually titanium, for the temples. The springiness of the temples lightly pinches your head to hold the glasses in place. This system results in a lighter weight pair of glasses, fewer components that could break, and a sleek design.
Clip-on sunglasses lenses are available for some eyeglasses frames. Clip-ons are simply frame fronts with plano sunglass lenses, no temples, and an attachment mechanism to hold on to the underlying frame. The clip-ons usually match the eyeglasses frame in shape and color, and attach either by clips or with magnets. Regular clip-ons require two hands to add and remove the clips, but magnetic clip-ons (hold to the frame with magnets instead of clips) can be added or removed with just one hand.