What a spring hinge is
A standard hinge is a pin through two or three interlocking loops, one set on the frame front and one on the temple, held by a screw. The temple swings closed and swings open until the loops meet, and then it stops. Push it further and something bends or breaks.
A spring hinge, sometimes called a flex hinge, puts a small coil spring inside a barrel at the end of the temple. The temple swings closed as normal, but when it swings open and reaches the stop, the spring lets it travel a little further outward, and then pulls it back. The travel is small and the spring is firm; the point is not that the temple flops about, but that it has somewhere to go when it is pushed, and comes back on its own. The types of glasses frames guide covers the other parts of a frame; this piece is about this one.
What it does
- It fits a wider head. A frame with a fixed stop has one width, and a head wider than that width pushes the temples outward permanently, which is the stretched-out frame the how to tighten glasses guide fixes. With a spring hinge the temples open to the head and press gently inward from the spring, so the same frame fits a range of head widths. This is why spring hinges turn up on frames sold for wide faces, which the glasses for wide faces and sunglasses for big heads guides cover.
- It survives the one-handed pull. Taking glasses off with one hand twists the frame and pushes one temple past its stop. On a fixed hinge that is how frames stretch and screws loosen. On a spring hinge the temple gives and comes back.
- It survives being sat on, mostly. A frame in a back pocket or under a pillow pushes the temples outward; a spring takes some of that instead of the frame.
- It holds a light frame on. A light frame has little weight to keep it in place, and a spring hinge adds a steady inward pressure at the temples that does the job the weight would have done. That is why the lightest frames in the range carry one; the lightweight glasses guide covers the materials.
- It keeps the screw tight for longer. The spring takes the sideways load that would otherwise work the hinge screw loose.
What it does not fix
A spring hinge is not a substitute for the right size. If a frame is too narrow by a wide margin, a spring hinge lets it go on the head, but the spring then presses hard all day and the temples sit at an angle, which is uncomfortable and looks wrong. The frame should be close to the right width with the spring doing the last part. The how should glasses fit guide has the width check.
It also does not change the bridge. A frame that slides down the nose slides because of the bridge, not the hinge, and a spring hinge does nothing for it. The fix there is a frame cut for a lower nose bridge, from the low bridge fit glasses collection, or an adjustment at the nose pads.
And it limits one adjustment. On a fixed hinge an optician can bend the temple at the hinge end to change the inward grip. On a spring hinge that bend is replaced by the spring, so the grip is set by the spring and cannot be bent tighter in the same way. The temples can still be bent behind the ear, which the how to adjust glasses arms guide covers.
Who should choose spring hinges
- Anyone with a wider head, or who finds that most frames pinch at the temples.
- Anyone who takes glasses off with one hand, pushes them up into the hair or wears them on top of the head.
- Anyone who wants a very light frame to stay put without a heavy acetate grip.
- Children, and anyone whose frames get sat on, stepped on or thrown in a bag.
Who does not need them: someone whose head width matches the frame and who treats the frame gently. On a heavy acetate frame with a strong natural grip the spring adds little, and a well-fitted fixed hinge can be adjusted more precisely. Neither is better in the abstract; the spring is better for the people listed above.
Spring hinges on sunglasses
Everything above applies to sunglasses, and in one respect more so. Sunglasses are taken on and off far more often than glasses, usually one-handed, usually pushed up onto the head, and a spring hinge is the difference between a pair that still fits after a summer and a pair that has stretched. Four of the five MUJOSH frames with spring hinges are sunglasses for that reason.
Caring for spring hinge glasses
- Open the temples with both hands and do not force them past the point where the spring resists; the spring has a limit, and pushing past it bends the barrel.
- Keep the hinge dry when cleaning. Wipe the frame with a damp cloth rather than running it under the tap for long, and dry the hinge end; the how to clean eyeglasses guide covers the rest.
- No oil, and no household lubricant. The spring is in a sealed barrel and does not need it; an oil draws grit and ends up on the lens.
- Check the hinge screw a couple of times a year. A spring hinge works the screw less than a fixed hinge, but it is still a screw.
- If the spring goes slack or the temple stays open, the barrel is replaced, not the frame. It is an optician's job rather than a home one.
MUJOSH frames with spring hinges
Five frames carry a spring hinge, stated on each product page. Prices as listed on 27 October.
- Alio XZ, $99: a crown panto eyeglass frame in ultra-light AQUA material with spring hinges and a low bridge fit, three colourways. The optical frame with the spring, and the one where the spring is doing the holding-on job for a very light front. In the eyeglasses collection.
- Turbo M0, $99: a square sunglass in AQUA material with spring hinges that adapt to head width. The entry sunglass with the spring.
- Velo M0, $135: a square-round sunglass in the same AQUA material with the same spring hinges, four colourways.
- Species BL, $135: an oversized square-round sunglass in acetate with spring hinges and a low bridge fit. The acetate frame with the spring, for a wider head that wants a substantial front.
- Futuristic, $159: a one-piece bent-lens sunglass in TR90 with hidden spring hinges, three colourways. The spring is inside the temple and does not show.
For comparison, the other hinge types in the range: Ultem uses a mortise and tenon hinge, a fixed joint with no screw through the loops; Screwless Polarized and Lady Lang are screwless, with nothing to work loose; and Beta Pitot has no spring but gets its give from beta-titanium temples that flex along their length, which the titanium glasses guide explains. The Ultem glasses guide covers that material's own flex. The rest of the range is in the sunglasses collection.
The bottom line
A spring hinge lets the temples open a little past straight and spring back, so one frame fits a range of head widths, survives the one-handed pull, and keeps a light frame on without weight. It does not replace the right size, does not fix a sliding bridge, and takes away one bend an optician would otherwise make. Choose it for a wide head, rough handling, a very light frame or a child; skip it on a heavy acetate that already grips. Do not force it, keep it dry, no oil. In the MUJOSH range, Alio XZ is the optical frame with spring hinges, and Turbo M0, Velo M0, Species BL and Futuristic are the sunglasses.
Frequently asked questions
What are spring hinges on glasses?
Hinges with a small coil spring in a barrel at the temple end, which let the temple open a little past straight and pull it back. The spring lets one frame fit a range of head widths and takes the strain when the glasses are pulled off one-handed.
Are spring hinge glasses better?
Better for a wider head, rough handling, a very light frame or a child. Not better in the abstract: a well-fitted fixed hinge on a heavy acetate frame grips just as well and can be adjusted more precisely.
Can spring hinges be adjusted or repaired?
The spring itself is not adjusted; the grip it gives is set. The temples can still be bent behind the ear. A spring that has gone slack is replaced as a barrel by an optician rather than repaired at home.
Which MUJOSH glasses have spring hinges?
Alio XZ (eyeglass frame), and the sunglasses Turbo M0, Velo M0, Species BL and Futuristic, each stated on its product page.
