If your glasses break at the hinge, you are left with few options: Replace the entire set of glasses at a optometrist, Or replace the hinge with a functional substitute. These are the glasses my wife wears at night after her contacts come out, so appearance was not a factor - only utility. She did want them to remain fold-able so they could go back in their case for travel and storage.
I found out that I could perform the operation with a donor from the hardware store sold as a hinge for small wooden crafts.
- Small Brass Hinge
- Super Glue
- Leatherman Pliers
- BIC lighter
Step 1: Hinge Removal
First, I grabbed the portion of the metal hinge that protruded from the frame with a set of leatherman pliers. Of course, you could use any type of needle-nose pliers for this step. I wouldn't use a heavier set of pliers like lineman's pliers, because they will take longer to heat up. The pliers need to heat up enough so that they can start to transfer heat to the hinge which will start to soften the plastic that is holding it in.
I thought about using a different heat source, like a soldering iron, to heat the metal hinge but thought that would just add a step because I still would have to use something to grab the hinge after it was heated.
Second, I used a standard BIC style lighter to heat the tip of the pliers' jaws. Care was taken to not heat or burn the plastic directly.
Third, I stopped applying heat with the lighter about every ten seconds and pulled the plastic frame to see if it would release the hinge. It seemed to only take about 30 - 40 seconds to heat the hinge enough to release from the plastic.
Overall, this method worked just like I had hoped.
Step 2: Preparing the New Hinge
This hinge was chosen because, as you can see with my wife's frames, the 5/8" width is a good fit even though I had to cut the length down quite a bit.
I used the wire cutting portion of the leatherman's jaws. First I cut as far in as I could from one side, then cut from the other side, making an almost complete cut. Next, I used my hands to fold the two halves back and forth along the cuts to separate the two pieces. I used the leatherman because it was convenient. If you have the right tool, use it. The proper tool for this process would be any one of the following: tin-snips, shear, cut-off wheel, hack-saw, etc.
After cutting down the length on both ends of the new hinge, I started to bend the side of the hinge that would be attached to the lens side of the frames. The plastic had a curve that I needed to match with the new hinge so the glue that would have enough surface area to contact.
Step 3: Attaching the New Hinge
As a welder, I am fond of the following method for attaching two parts together: 1) Hold the parts together with pliers, 2) "tack" in one or two spots and continue to hold the parts until the "tacks" dry (15 seconds for super-glue), 3) remove pliers and glue the parts together entirely. The original (non-gel) super glue tends to wick nicely into the tiny gaps between the parts to be glued and I also made use of the holes that were already in the hinges as another glue location.
I glued the hinge to the lens side of the frame first as I knew the earpiece would be easier to adjust for the final alignment of the two parts. I noticed that for some reason if I lined up the earpiece to be level and symmetrical with it's counterpart while the glasses were open, it was slightly "off" when closed. I decided to leave it that way because the fit and comfort during use was more important than having them line up when closed.
After the hinge was fully glued and the glasses were one again, I set them aside so the glue could completely dry. I ended up leaving them for about 45 minutes before putting them in use.
Step 4: Finished
In a blind (or low-visibility) test, they function nearly the same as new. The hinge offers very little play and they fold nicely for storage.
The new hinge is an eye-sore, but is mostly hidden behind the brown plastic frames. After spending $1.00 on hinges, a little glue, and about an hour of my time, I am quite satisfied. More importantly, my wife thinks they're great and I have chalked up a few points for husband of the week.
Thank you for reading through this instructable and I look forward to any feedback or questions!