I bought a pair of Nike sunglasses with flexon frames a few years back. They were the only pair in the whole shop that would fit around my gargantuan head. I used to crumple up my sunglasses in an impossible shape just to amaze my friends when they bounced back. That finally came back to bite me when the bridge snapped and I suddenly had two pairs of sunglasses for one-eyed pirates. The flexon alloy doesn't lend itself to being soldered directly and there just isn't enough material to tape (not that I would where them in public like that, but I did try). I needed a tube made of a metal that bonded well with lead and tin that I could insert both sides of the bridge into and solder. D&J Hobby on Saratoga Ave in San Jose had just the right tubing from K&S Engineering. For this project, you will need:
- Small pliers
- a saw, small tube cutter or abrasive cutoff tool to cut the tubing
- Soldering iron
- rosin core solder
- Acid Brush and Alcohol to clean the rosin after the repair
- A dab of clear finger nail polish
- 0.25 - 0.5 inches copper tubing with an inside diameter slightly larger than the outside diameter of your bridge. Square tubing is available if the bridge you are repairing isn't round. ( http://www.djhobby.com/ (retail) or http://www.ksmetals.com/ (wholesale))
Step 1: Assess the Situation
You have a pair of eyeglasses that has a broken bridge. My pair had a bridge made of flexon. It not perfectly round, about 1.6mm x 1.3mm. You will have to select a tubing that has a slightly larger inside diameter to make the repair. The tubing I found was only spec'ed with an outside diameter and a wall thickness. It turned out to have a 1.7mm ID. I aligned the two pieces at the break and saw that the bridge was curved. My first attempt at a repair splint followed this curve. It turned out to be too difficult to bend the small tubing precisely enough without jewelers pliers which I don't have. When I dry fitted the splint I could never get the two halves of the glasses to align correctly. I scrapped the curved splint and went with a much shorter straight one.
Step 2: Cut the Splint
Step 3: Solder the Splint in Place
Step 4: Final Steps and Conclusion
Dab some clear finger nail polish over any exposed solder. Solder is made of lead, no sence in giving yourself lead poisoning.
The finished product isn't perfect, but it will get me through the next few weeks until I can get annother free pair of glasses with my vision plan. With some jewlers pliers I would be able to bend the tubing more precicely allowing both a much more astetically pleasing repair as well as maintaining the alightment of the two lenses.
Annother idea would be to combine a medium wieght solid wire with some shrink tubing. The wire should be much easier to bend and result in a more flexible end product. My very first attempt at a repair was forcing a piece of stripped insulation off of some solid-core wire I use for breadboarding. It held up for exactly one use before it ripped right at the break. It also didn't provide enough ridgitity.