If you are reading this, you probably have a resin(plastic)-cased wristwatch with a broken lug. The lug being the place where the watch band attaches to the watch case.
The question you need to ask yourself is, how much effort do you want to go to, to fix a cheap resin-case watch?
In my case, I was so irked by the thought of tossing a functioning wristwatch into the trash that I started small and just kept ramping it up until I finally got a repair that stuck.
What finally worked, for me was to glue the steel watch band to the steel case back, using a thin patch of baking soda and superglue that spanned the watch back and the first links of the metal watch band. In effect, I bypassed the resin case and broken lug entirely.
Edit 9/1/2024: This repair is not waterproof. Which, in hindsight, should not be a surprise, as regular superglue isn’t waterproof. After about a month, the repair separated cleanly from the underlying stainless steel following several hours of outdoor exercise in the Virginia summer heat.
The obvious solution would be to use dishwasher-safe super glue, but that’s too thick. Neither one I tried would soak into the baking soda.
So I redid the repair using the same regular liquid superglue as I used the first time.
I wear the watch every day, and the second repair is holding up fine as of 11/19/2024. Based on that, I’m going to claim that this makes a permanent repair, as long as you don’t get it soaking wet.
The original post continues below.
Ultimately, I chose this method because superglue has a reputation for adhering well to stainless steel. I’m not sure how well it would adhere to a plastic (resin) strap. But I wouldn’t rule it out. If nothing else, the mix’s adhesion to stainless was way above my expectations.I’d be willing to try the same repair with a resin strap. Certainly if the alternative is to throw the watch away.
You can’t see the repair when wearing the watch (a Casio A158WA).
And you don’t want to see it, when you take the watch off.
Despite the looks, the watch is still comfortably wearable, and the repair seems to be holding up well.
But the reality is that nothing else even came close to working.
Plus, it’s cheap and easy. My only cash expense was for a new battery, because it seemed prudent to change the watch battery before doing this. Once I figured out what to do, the repair itself took just a few minutes.
If that’s success, what were the failures?
Source: WalMart.
The best way to understand why I ended up with this expedient repair is to see what didn’t work. In particular, these four approaches failed:
A drop of superglue on the lug takes essentially zero effort, but was a total fail. Couldn’t even get the watch back onto my wrist before that gave way.
A drop of two-part liquid epoxy on the lug, ditto. The act of buckling the clasp broke that free.
A small amount of JB Quik (two-part epoxy paste), applied between watch body and watch band, failed after a few hours. It didn’t stick well to either the plastic case or the stainless watch band.
A larger amount of of two-part epoxy paste (JB Weld’s Quik Weld), applied as a patch across the stainless watch back and stainless watchband, held for almost a day. But the JB Weld adhered poorly to the stainless steel, e.g., it was easily removed with a knife.
Why did this repair work?
To summarize the failures:
- Glues don’t stick well to plastics, no matter what anybody tells you.
- If you try to fix the lug itself, the surface area you’re working with is tiny, so there’s little area for the glue to adhere to anyway.
- The resulting piece of hardened glue/epoxy is so tiny that it has little physical strength.
All of which told me that I needed to:
- Glue to some surface where I could get some adhesion.
- Glue to a much larger surface.
- Use a much larger patch, so that it has some physical strength.
The breakthrough was in realizing that a) this was a $20 watch, b) the battery lasts seven to ten years, and so c) there was really nothing to stop me from literally gluing the watch band to the watch back. Basically, just take the plastic case and plastic lug out of the equation entirely.
I chose superglue because it has a good reputation for sticking to stainless steel.
But I also needed a physically strong patch, because it needs to keep the watch band rigidly attached to the watch. That way, the broken lug simply doesn’t matter. All the force between watch and watch band is transmitted through the glue patch.
That suggested trying the baking soda and superglue hack. I had always thought that was just internet-based nonsense, but in fact, there’s some good chemistry behind it (reference). Assuming that reference is correct, the baking soda isn’t merely a filler, it actually cures the superglue in a completely different fashion from what would normally happen. The result is stronger than superglue alone, and has better adherence to whatever you’re trying to glue to.
Instructions, such as they are.
In any case, the repair was simple. In concept. The tricky step is wetting the powder with the glue, which turns out to be a timed test, as the superglue sets rapidly under these conditions. If you try this, and read nothing else, read the paragraph below on wetting your baking soda with superglue.
- Scrub the watch back and the watch band to remove dirt and oils. Dry them.
- Gently re-attach the watch band to the watch, using the broken lug. This doesn’t have to be physically strong, it just has to look OK. The repair itself is concealed on the back of the watch.
- Set that face-down in a position that approximates the curve of the wrist. (Because one or two links of the watch band will end up rigidly attached to the watch case, if this repair holds.)
- Lay and sculpt your baking soda. Spoon on and smooth out a bit of baking soda, being sure to cover a large area of both the watch back and the watch band, and making it thick enough that it will have some physical strength. And yet, not too thick, or it’ll be uncomfortable to wear. I was shooting for something about as thick as the pad portion of a band-aid.
- Wet your baking soda with superglue. Slowly drip on liquid (not gel) superglue until the baking soda is saturated. I used most of a one-gram tube of Ace Hardware Future Glue liquid super glue. See below for greater detail.
- Dust a little more baking soda on, to cure any liquid glue remaining on the surface.
- Let it sit for five minutes or so.
- Clean up any excess glue using a sharp knife.
- Use a bit of sandpaper to smooth out the surface that will touch the wrist.
In hindsight, cleanup would have been a lot easier if I’d taped over the parts where I didn’t want glue to stick. But it wasn’t hard to remove the excess glue with a knife.
I don’t know if this baking-soda-and-superglue patch will stick to a resin band. But it should be easy enough to try it and find out.
Wet your baking soda with superglue, some details.
The tricky step in this repair turned out to be wetting the baking soda. It’s a timed test, because the baking soda/super glue mix sets up fast. And it’s critical to wet the baking soda patch thoroughly with superglue, because where you don’t, it won’t stick. For sure, you need to get the full depth of the patch wet with superglue, all the way down to the substrate (e.g., stainless steel, in this case).
On the plus side, you’ll be done with it before you know it. Because it behooves you to move fast. Once I figured that out, I essentially paved the top of the baking-soda patch with closely-spaced drops of superglue.
I can tell you from experience that you pretty much can’t go back and fix any mistakes. So if you (e.g.) get too little glue on a spot, by the time you go back to re-wet it, the top will already have skimmed over with hardened superglue, and you’re out of luck. For a couple of “dry pockets”, I ended up using the tip of a knife to pierce the thinnest part of the dried layer of the superglue, then added fresh superglue.
Separately, in the end, I wish I’d done more (or, really, anything) to prevent adhesion of excess glue and excess glue/baking soda mix. I wish I had used some tape, or light oil, or similar. As it was, I ended up using the tip of a sharp pocket knife to scrape off excess glue and glue/soda mix. FWIW, that’s a task that you should do as soon as feasible, e.g., before the mixture has had hours to cure.
An irrational repair?
To be clear, this is a cheap watch. I could replace this watch — literally a more-recently manufactured clone of the unchanged model — for about $20.
But I like this watch. It’s lightweight. The only material that touches skin is stainless steel. The quartz works are guaranteed accurate to within 30 seconds a month (or about twice as accurate as the best mechanical watches.) This particular watch only gains seven seconds a month. This makes the watch low maintenance, in that it stays within a minute of true time as long as I set it twice a year for the change in daylight savings time. It’s waterproof enough that I can scrub the schmutz off of it.
And it’s simple. Unlike any other digital watch I have owned, I can use all of its functions without reading the manual.
It has some faults. The LED back-light is comically dreadful. And the clasp is insecure in several ways. And, as I now know, the plastic case is a potential failure point. But Casio does not put this works into a metal case.
Anyway, I already own it. And I hate tossing stuff that’s still (mostly) working.
Once I made my mind up to try to fix it, I was just too stubborn to give up.
Boiled down
How much effort are you willing to go through, in order to keep wearing a cheap plastic-bodied watch with a broken lug?
If you already own baking soda and liquid (not gel) superglue, it will take you just a few minutes to try this repair.
The big surprise was how strong and adhesive the super-glue-and-baking-soda patch is. Before this, I had assumed that was all internet hype. But, in fact, there’s good science behind it. And in this instance, it worked better than JB Weld epoxy, which is high praise indeed.
And when you get right down to it, what have you got to lose? If it doesn’t work, then you are left with a broken wristwatch. Which is what you already have.
