Eyeglass Repair--broken Monofilament Lens Retainer





Introduction: Eyeglass Repair--broken Monofilament Lens Retainer

About: I miss the days when magazines like Popular Mechanics had all sorts of DIY projects for making and repairing just about everything. I am enjoying posting things I have learned and done since I got my first ...

I was sitting on the sofa reading and my right lens suddenly dropped onto my lap without warning. The monofilament (fishing) line broke from several years of normal wear. I was very thankful this did not happen while I was doing quite a number of other things I normally do, like riding my bike on a country road.

It was the weekend and my optometrist's office was closed. I am a pastor and had to lead the worship service on Sunday without my glasses. There is a lot of reading involved. I got by with a pair of reading glasses, but everything more than fifteen feet away was a big blur.

I searched the Internet for eyeglass repair. There was nothing about replacing a broken monofilament lens retainer.

Step 1: Anatomy of an Eyeglass Frame

The parts of an eyeglass frame where the monofilament line attaches to hold the lens are very small. The colors of the frame and of the line blend into one another much more than shown in this drawing, especially when you are looking at them without your regular glasses.

The left portion of the drawing shows the end of the frame if the glasses are upside down on a countertop as in my first photo and you are viewing the frame from the side where the bows attach. There are two small holes near the end of the frame. The monofilament line loops through these holes. The 90 degree bends the line must make keep the line from slipping when the lenses are in place. The graphic in the next step will give you a clearer picture of how that works.

The right portion of the drawing shows a cross section of the metal in the frame and the channel on the inside of the frame where it contacts the lens and supports it. The gray circle is a cross section of some monofilament line permanently embedded in the frame. There is a corresponding groove around the circumference of the lens and that groove fits over the embedded monofilament line to keep your lens in place where the frame goes around the lens.

Step 2: The Line's Pathway

The drawing shows the pathway the line makes through the holes at the ends of the frame. The left portion of the drawing shows the line (gray) and the frame (brown) as viewed from the side of the glasses near where the bows attach to the frame. The right portion of the drawing is a side view and shows the bends the line must make. The lens would fit against the left side of the view in the right portion of the drawing. The stubby end of the line is supposed to press down into the channel so it does not interfere with the fit between the lens and the frame.

See my Instructable titled "What gage is that steel or wire?" to determine the thickness of the monofilament line your glasses use. Or, try to match up the end of a spool of line when you are in the sporting goods department of your local store. It appeared 0.029 thick 50 pound test line should have worked, but it would not thread through my holes without a lot of work forcing it. I chose 0.022 thick 30 pound test line. A spool of 400 yards was about six dollars US.

Use a knife point to pry the old broken line out of the frame holes. Attach the end of the new line as shown at the end of the frame near the nose pads. Place the lens into the frame and pull the line over the circumference of the lens. Cut the line so it is an inch or two longer than needed.

Remove the lens and thread the end of the line through the frame holes near where the bow attaches. Before trimming excess line, place the lens in the frame and pull the line over the lens. This will show you how much you need to cinch up the line so it will be tight when the lens is permanently mounted. Remove the lens and adjust the length of the line between the ends of the frame. Keep working at this until the lens will be held firmly by the line.

Trim the line to length and try to press the stubby end into the channel. I was not able to get it to go into the channel, not even with a needle nose plier. My lens seems to stay firmly in place, anyway.

Step 3: Mounting the Lens

In the photo the monofilament line is represented by the red line I drew in a photo editing program. This photo shows the way to proceed in order to secure the lens in the frame with the line. Pull the line up over one corner of the lens and hold it there with your fingers.

Step 4: Mounting the Lens--step 2

Move your fingers along the lens pulling the monofilament line over the lens and into the groove for the line. Finally, roll the line over the other corner of the lens.

My frame does not fit around the lens quite as tightly as when the glasses were new from the factory. But, the lens does not wiggle and it seems to work very well. I wish I had thought of all of this on Saturday evening when my lens fell onto my lap. I could have gone to the sporting goods section at our 24 hour big box store and had my glasses working for me again after about 30 minutes of work.

I have not checked yet with my optometrist to see about an official repair of my monofilament line. My wife talked with someone at church Sunday who had experienced the same problem. She had to send her glasses away for several days to get a new monofilament line installed. One listing in the search engine when I was looking for information on replacing the monofilament line appeared to advertise various repairs to eyeglasses. It appeared that business was charging $25 US for replacement of a monofilament line. Who knows? Maybe my optometrist would do it for free while I wait. But, he will not be open for a while yet, and I am using my newly repaired glasses as I am preparing this Instructable.



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    Thank you so much. I spent over an hour calling the surrounding walmart vision centers on a Sunday with no luck. All were closed so i googled a diy on fixit myself. What a breeze thanks to your instructions. I got it done in less than 10 minutes. Thank you again!

    2 replies

    Thank you for your comment and welcome to Instructables. I am glad it was helpful to you. These things seem to happen on weekends or when stores are otherwise closed.

    I am trying to locate a monofilament reading glass vendor.

    Any suggestions?

    Good instructable. I also watched a video about the process on youtube but your instructions and diagram really closed the loop on the process and gave me what I needed to jump in and do it. I just fixed my daughter's glasses as good (or better) than new. Thanks!

    1 reply

    I am glad it helped you. I look at more things on YouTube in recent months than I did formerly. Thank you for the reminder that many useful things are demonstrated there.

    I love these glasses, and it took 2 years to buy them, they survived world travel, crushing weights, and near destruction (aka they were trapped under an upside down car and buried by it for a week before being recovered and still no damage), and were still ticking.

    After all that abuse of my glasses (when the glasses were 10 years old) the line broke when cleaning!

    This post is so cool. I wanted an eye-doctor guy to do it for me and to just pay him, but my wife insisted I try self repair. Found this post, and took awhile to find the right line. After going everywhere went to Walmart and found matching 30 lb Omniflex .023 mm line. It took about 15 min to thread but a perfect repair at the end with the same strength, color and feel as the original. Your post is amazing is how well it explains why I thought would be impossible to do and makes it very easy.

    1 reply

    Thank you for the good report and congratulations on your success. I hope you are now a giant in your wife's eyes.

    Nice! I broke my glasses last night and spent about an hour straightening the frame but figured I'd have to pay big $$ to get the lens put back. Now, with a few inches of 30lb test line from Walmart, I'm good to go! Thank you for putting these instructions up! Total cost for the fix... $1.99!!! And it only took about 5 minutes!

    1 reply

    Thank you for commenting. I am glad this helped you.

    I inadvertently left my glasses sitting on my dash board one hot day, and came back to find that the heat caused the lens to expand, popping the mono-filament.
    I had bought them at walmart eye clinic. I took them in, and they fixed them while I waited. I had no idea the lens was held in place by monofilament before that happened. Your instructable will come in handy one day.

    1 reply

    Thank you for looking at my Instructable. It is good you were able to have your glasses fixed easily. When mine failed, no such stores, especially the one I use, were open. For times like that some fishing line in the workshop is handy. The one difficulty I experienced is that it is difficult to see without your glasses while working on your glasses. I had bought some reading glasses for use in pistol target shooting, and they helped a great deal, even though they were not perfect.

    Great instructable. I'd just like to add something that wasn't totally obvious when I first read it...

    On mine, one end looked just like yours, and the line went in and out and tucked under the lens. On the other side, though, the line just went into a hole and stopped. It wasn't clear how this line stayed in place. I pulled the fishing line through this hole, then heated the end with a lighter and tapped it against the desk to flare the end. That seemed to hold just fine while I tensioned the other end as described.

    I'm an optician, and I'll say you've come very close to what we do. I would offer a couple of suggestions in case this should this ever happen again. By adding these simple steps, you'll get the lens in there as tight as day one.

    When you have first threaded the line through to size it up for length, place the lens in the frame (and the line into the groove along the lens' edge). Now, pull the line as tight as you can within reason. You should be beginning to actually stretch the line a tiny, tiny bit. While keeping the tension, pull the line at a sharp angle so that it makes a slight kink in the line.

    Release the tension and remove the lens. The kink should still be visible and can now serve as a marker. When you insert the line through the second hole to secure it, feed the kink through that second hole a few millimeters so that it just comes out on the inside of the frame. This will ensure that the hold will be slightly tighter than when you were applying tension.

    Now use the ribbon method mentioned earlier. All you do is put the lens back into the frame and pull the line up over one corner of the lens and into the groove. Next, take a three or four inch length of satin ribbon and loop it around the line. Use the ribbon to pull the line over the edge of the lens and the line will snap tightly into place. Afterwards the ribbon should slide right back out by pulling on one end.

    One word of caution: If the line is so tight that you really have to pull excessively hard, take a step back and loosen the line. If you go crazy and make the line ridiculously tight it can chip the lens edge when you force it over. Keep in mind, you should have to use a good bit of effort to get it over, just don't go overboard.

    Another little trick if it is still a little loose after all is said and done: (Leaving everything assembled as it is) Heat the line for about thirty to forty seconds with a hair dryer on high. Immediately afterwards, dip it into ice water. This will tighten it right up. As long as you live in the U.S., this will not damage the lens (they go through much harsher temperature changes during production). In Europe or Asia, however, do this at your own risk. The standards for treating glass are much different overseas. The upside is that they can get glass much thinner than we could ever dream of here. The downside- it does not take much to shatter it. Also, an optician in the U.S. would lose his license for putting a glass lens into a semi-rimless frame like this. On the other hand, it is still very common to see it done in Germany and Italy. I've also seen one done in Hong Kong in which the lens was barely wider than the line. It was a very impressive piece of craftsmanship, but I would be terrified to wear it.

    Also, just so you know, most opticians should make this repair for you at no charge. They may not be thrilled about it (it is fairly time consuming for a busy practice/lab), but most will do it with a smile.

    One last point- The "Sarah Palin" style frames (it is incredibly annoying that they have been so thoroughly connected to her, in reality they've been around for decades) actually don't use a groove-and-line system like this; the lenses are actually drilled through and mounted with screws. Just so you know.

    Hope this helps in future dilemmas.

    2 replies

    Thank you for your detailed and informative comment.  Thankfully, my lenses are plastic, not glass.  As I mentioned, this problem developed for me on a weekend when all of the shops were closed and I needed glasses early the next day.  I posted this for the benefit of anyone with a similar problem, but unable to get to a shop for a repair.

    it's polycarbonate plastic, a plastic used in CDs and bulletproof windows (except the one that nasa uses, those are silica-fused glass)

    I have a pair of glasses just like it with a broken foot/leg? (what goes over the ear). It's broken at the hinge. Can any body help?

    1 reply

    We call it a temple. Unfortunately, if the hinge itself is broken, there is not much that you can do. On most frames the parts in and around the hinge are too small for even a jeweler to solder and still keep functional.

    Your best chance is to see if the frame is still current (as far as production) and try to order a new temple or frontpiece- depending on exactly where the hinge is broken. Cost-wise it will usually set you back about 1/4 to 1/3 of the original price of the frame.

    Before you do that though, make sure that it is not just a problem with the screw. I know that sounds ridiculous, but on some of the more intricate frames, people commonly assume that the hinge is broken but it turns out to only be a missing or defective screw. Best of all, that repair is free.

    contacts are way better

    Why do pastors and missionaries often use those glasses that have no rims on the bottom? I remember Douglas Addams making an observation about this in the book "Last chance to see". Anyway, good instructable.

    1 reply

    Oops! I misunderstood. I thought you meant the little half glasses people wear on the end of their noses. Then they look over them. My glasses have no frame, but monofilament line, on the bottom because that was what my optician was pushing the year I last got new frames.