How to Repair Broken Eyeglass Frames

Here's the procedure for repairing metal eyeglass frames. This will take about 5 minutes for the actual repair, 10-15 minutes to polish the metal, and about six hours to find the screws to reassemble the eyeglass frames. The cost of the materials is about the same as the cost of having a single repair done by a professional. If your glasses break more than once, repairing it yourself as shown here will be cheaper than taking it to a repairman.
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January 1, 2004; updated Nov 28, 2010

1. Soldering

  1. Clear some space on your workbench, like this. This will make it much easier to work.

    Soldering bench

  2. Assemble the supplies. For all practical purposes, it's impossible to create a strong joint by butting the two ends together by soldering. Therefore, we will use a small piece of metal to reinforce the broken area. The ideal thing to use is a short piece from an old pair of glasses, ideally made of the same metal. Alternatively, part of a metal bobby pin, piano wire, or any other flat piece of spring steel, may be used. Most eyeglasses are made of silver-nickel or gold-plated steel, which are easy to solder.

    Nowadays, more and more eyeglass frames are made of titanium. Titanium is probably the best metal for eyeglasses because it's 42% lighter than steel and has the same thermal expansion coefficient as glass. However, titanium is very difficult to solder unless it's been coated with some other metal. Titanium is usually alloyed with vanadium and aluminum, which make the alloy stronger. Titanium, vanadium, and especially aluminum form surface oxides that make it difficult for solder to adhere to them.

    Some other types of eyeglass frames are too springy to solder effectively. The problem here is that the solder is not as flexible as the underlying metal, and the joint eventually works loose or cracks when the frames are flexed too many times. These frames must be brazed or welded (see below).

    You also need a two-inch piece of 24-gauge copper wire.

  3. Unscrew the side-arm from the frame. If it can't be unscrewed, carefully remove the lenses and place them aside. Remove the plastic earpiece so it doesn't get burnt. Use sandpaper to thoroughly clean both pieces. Touch the pieces only with forceps, not with your fingers. Grease from your fingers, dirt, corrosion, or any coating on the metal will result in a weaker joint or prevent the pieces from sticking.

    Soldering pieces

    The side-arm in this example was not completely broken, but contained a weak area at the point where the metal becomes narrow. This made it possible to use a single clamp instead of two clamps.

  4. (Optional) Use a file to cut some diagonal grooves or shallow scratches on the inside face of the small reinforcing piece. This will create a small space between the parts so the solder can flow between them and act as a glue, which will make the repair stronger.

  5. Clamp the reinforcing piece to the inside of the broken arm using one or two small alligator clips (available from electronics stores). Wrap the copper wire around both pieces to hold everything together.

    Clamped pieces
    Clamped pieces with 2 clamps

  6. You will need some silver core solder, flux, and a lighter. Make sure the solder and the flux both say "lead-free". The temperature of the torch is high enough to evaporate lead. If you use solder that contains lead, not only will the repair not work, but you and everyone in your house will also get serious lead poisoning.

    Solder

    If your eyeglass frames are made of gold-plated metal, use gold solder (available from a jeweler's store or various Internet sites) instead of silver solder if you want the colors to match.

  7. You will also need a propane torch. Keep it far away from flammable solvents like acetone, as shown here.

    Torch

    Naturally, a smaller torch would be better.

  8. Put some flux on all sides of the assembly. The amount shown here is more than is needed, but excess doesn't cause any harm. The flux prevents oxygen from oxidizing the metal, which would prevent the pieces from sticking.

    Flux

  9. Heat the assembly for about 1 second, touching solder to the top part. Keep the solder behind the assembly to minimize direct exposure of the solder to the flame. The solder will be melted by the metal and will be sucked between the pieces by capillary action. The clamps can be removed if desired to prevent them from being ruined by the solder. Warning: don't heat near a joint. Many frames are held together by brazing and heating it will cause the pieces to come apart.

    Burning finger

  10. If the piece is not entirely covered with solder, remove the copper wire and add the clamps above and below the soldered area. Add more flux and apply the flame again. The piece should be completely and evenly covered with solder. If the copper doesn't come off, cut the ends and leave it in place.

  11. Remove any rough edges or leftover copper wire with a file and sand the metal first with 220 grit alumina sandpaper, then with 600 grit sandpaper.

    Finished piece

    The piece should look like this, with a convex bead of solder at both ends of the piece. There shouldn't be any solder on the outside of the piece. Once this is polished, the reinforcing piece will not be noticeable from the outside.

  12. If desired, the metal can be polished using the items shown here: a buffing wheel, a stick of polishing compound (left), and high-gloss polishing compound. Note the goggles, which are essential during this step. A Dremel tool with a small buffing wheel can be used instead of a buffer; however, only use the lowest speed on the Dremel tool, otherwise the piece will heat up and ruin the joint.

    Buffing supplies

    Polish the end of the eyeglass arm so the plastic earpiece easily slides back. Thoroughly clean everything before touching your lenses. The buffing compound will easily scratch plastic as well as glass lenses.

    Update: I found that hand-polishing with a product called Mother's Aluminum Polish works even better.

2. Brazing

Eyeglass frames can also be repaired by brazing. Brazing produces a much stronger repair than silver solder. Your eyeglasses will be almost indestructible.

The supplies that are needed are:

  1. A propane torch. A propane-air torch can heat small items to a high enough temperature to melt brazing rod. For larger items, you would need to use something hotter, such as propane-oxygen, MAPP, MAPP/oxygen or even acetylene. But propane/air is ideal for very small items. The MAPP torches available in hardware stores are often useless, because they only have two settings: ``off'' and ``incinerate''.
  2. Brazing rod. There are many types of brazing rod, including: The most convenient is the type that is coated with flux. A smaller diameter rod is preferred when using a propane torch, because it's easier to melt.
  3. A hands-free clamp.
Procedure
  1. Disassemble the part as much as possible to avoid damaging the lenses or any small screws.
  2. Clean all the parts with a wire brush. Make sure the metal does not contain any toxic coatings, such as lead, cadmium or zinc. If the metal is galvanized, brazing should be carried out in a fume hood.
  3. Clamp the parts into position using a hands-free clamp. Leave a very small gap (less than 1 mm) between the pieces to allow the metal to flow into.
  4. Heat the brazing rod first until the flux starts to melt. The flux should flow over the parts as a clear watery liquid.
  5. Next heat the parts until they are orange-hot. If the parts cannot be made hot enough to appear orange, they are too big. If you clamp it too closely to a large metal object like a vise, it will conduct heat away too fast, making it impossible to heat to a sufficient temperature.
  6. The brazing material will eventually melt and be sucked between the parts by capillary action. The hottest part of the flame is the clear area just beyond the inner blue flame. The blue flame itself should not touch the metal.
  7. Wait for the parts to cool in air several minutes before cooling with water.
  8. Remove the flux by sanding or wash in 30% sulfuric acid.
  9. File any rough edges and polish it.
The disadvantage of brazing is that heating steel to this temperature can weaken it. For example, heating a spring is likely to cause it to lose its springiness. Clamp something solid around the piece to prevent heat from being conducted to any screw holes or springs. Be careful not to heat near brazed joints (such as the nosepiece) or the existing joint may come unbrazed. Also, the metal should be heated just enough to make a good bond. This is not a major problem for the titanium or silver/steel alloy used in most eyeglass frames, because tensile strength, resistance to bending, and modulus of elasticity (springiness), are more important than hardness. For other types of steel, the rate at which the steel must be cooled depends on the type of steel and the properties needed. Some grades of steel have to be quenched in a salt or oil bath or annealed by gradually lowering the temperature. Carbon steel can also decarburize at high temperatures, which will reduce its hardness.

Needless to say, brazing should always be done in a well-ventilated area. Avoid heating brass, which can release zinc fumes. Brazing small parts, unlike welding, does not release significant amounts of carbon monoxide. Avoid brazing rods containing cadmium.

3. Welding

The ideal method for repairing eyeglass frames, especially those made of titanium alloy, is welding. This requires special equipment similar to that used by dentists. Welding is beyond the scope of this document.

Update (Nov 28, 2010)
Ilia Jerebtsov writes that silver soldering did not work for his eyeglass frames. It seems that some types of metal are too flexible for the solder to stick. However, he was successful with brazing:

A micro-torch, even though the box says it has a flame temp of 1300°C, won't melt brazing rod, I found out. Apparently the working temperature is much more important and is often not mentioned. In the end I successfully used a nickel silver rod with a 1700°C flame / 650° working torch. It took me just a couple of seconds and about half a cm of rod to do it.

Something worth noting is that if the frames are half-rimmed, like mine, the lenses are secured by a nylon string that goes through little holes. I had to re-drill them after the brazing. I used a 1mm bit with my Dremel. It's not very hard with the precision attachment and a magnifying glass. Also, fishing line is a perfectly good replacement for the string. I was under the impression that you need some kind of secret glasses wire that only opticians have, but nope, it's just fishing line.