WS 23 How to make a Clasp lock firmly again

1. Clasps with a Retaining Hook (most popular today)
2. Alternative Method for Clasps with Retaining Hooks
3. Older Rolex Clasps

4. Integrated Folded Clasp
5. Butterfly (integrated) Clasp
6. Other Clasps- Additional Help

Tool selection:

Leatherman tool vs. Watchmaker Pliers (recommended)

 As an example: Augusta #9551
Watchmaker Pliers with smooth jaws

I do not recommend to use a Leatherman or a multi-purpose pair of pliers with toothed jaws as those will leave "bite marks" on your clasps! If you are working on the Butterfly Clasp you will also need a small hammer and eventually a small vice with smooth jaws or any other device that lets you to a "scratch free" bending operation (Method 2).

1. Clasps with a Retaining Hook (most popular today)

Problem: Clasp too loose (1), rattling safety (2)
Claps of bracelets will over time and if opened daily loosen a bit. Also safety lock loops might start to rattle a bit.
But this is a problem that is very easy to solve, just two steps and both of them are explained below:

While a professional would probably use a tool like a watchmaker's pliers to bend down the retaining hook (1), I think you could use a plastic pencil or a peg wood. I would not recommend a screw driver, because if you slip, your clasp's inside - although invisible - will have a ugly scar. Just press down the little hook a bit and then check the clasp locking.
The same iterative process is recommended if the safety lock (2) is rattling or not locking tight.

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2. Alternative Method for Clasps with Retaining Hooks

An alternative method is to change the curvature of the folded clasp. The instructions are in the picture below.

Please note, it takes only a fraction of a millimeter! Patient iterations is always a great way to go.

Sometimes a combination of slightly bending the retaining hook (section1) and changing the curvature of the folded parts (this section) might work best. As always, make small changes, then test, then make more changes if necessary.

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3. Older Rolex Clasps

Older Rolex Claps often simply use two little flaps on the clasp cover to retain the bracelet in a closed position. Simply push both those flaps (1) a tiny bit inside, and the pressure at the locking position (2) will increase. In order not to clutter the image, I provided only one arrow at position (1). Of course you would bend both flaps symmetrically towards the inside.
As you can see, I had to do this on this Vintage Rolex because the bracelet was quite loose. And now it locks perfectly again.

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4. Integrated Folded Clasp

This is a clasp that is also generally called an integrated clasp, because it is barely visible when closed. Please note that a fair share of integrated clasps are of the so called Butterfly style which is discussed in section 5.

An integrated folded clasp. The majority of integrated clasps are of the Butterfly style, see below

Adjustment of this one is fairly straight forward. Simply spread the flaps at (1) a tiny bit and the locking pressure at (2) will be increased.

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5. Butterfly (integrated) Clasp (please be very careful here, only for people with a bit of experience working with metal)

I am repeating myself, but it is really important to understand that you are working with fractions of millimeters here. And if you have never worked on your car, motorbike or any mechanical appliances, then it might be much simpler to see your watchmaker to have the Butterfly Clasp adjusted.

The next picture explains how must Butterfly Clasps lock: The bar (a) basically locks with the edge (b). Again in order not to clutter the picture, I am showing the locations only for the left side. In most cases you will have to work on the right side as well.

Butterfly Locking Mechanism: bar (a) locks at edge (b)

Please note that I have exaggerated the bending of the red part for Method 2 for reasons of better illustration

As the picture above shows, you have basically two alternatives.

Method 1 would be to hammer (careful!!!) the bars (a) towards the inside thus increasing the pressure at edge (b). Again, it probably takes only 0.2 to 0.3 millimeter and you will experience a much firmer lock of your Butterfly clasp!

Method 2 is really only for the experienced. I have seen a watchmaker doing this for me. You will need a vice with smooth jaws! Very carefully bend both outer parts (in picture I show the left side only) towards the red arrow direction. Please note that I have exaggerated the amount of distance. Again, 0.2 to 0.3 millimeter will most likely do the job already. By bending the inner part's both ends, the distance between  b  and  a  will slightly decrease and thus the locking pressure will increase.

Please note that there is a huge variety of different Butterfly Clasps out there. The one shown above is a pretty common and simple mechanism. A more modern and easier adjustable is the one below. Adjustment is a lot easier since one only has to bend the two flaps in arrow direction.

If your clasp does not look the same way, I am sure you can figure out how the locking pressure is applied. Simply open and close the clasp (of course you are not wearing the watch now) and also check how the clasp locks from the inside of the bracelet. If you are not sure, then please read section 6.

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6. Other Clasps

There are a lot of different clasps out there. Luckily today Japanese watch brands like SEIKO, CITIZEN and CASIO have started to introduce push button operated clasps on almost all their watches. That of course renders the above methods obsolete.
However if you find that your clasp uses a different way of simple pressure locking, then I suggest you study the locking mechanism carefully and I am sure you will find where to push or bend a bit in order to increase that locking pressure. As I mentioned above: patient iterations are the way to go. Adjust a tiny bit, test the effect, eventually adjust some more. You do not want to bend metal too often as metal will show a so called tiring effect and eventually crack. But with a couple of small adjustments, you will always be on the safe side.