Components of a Dive Watch


There is a lot of stuff going on with a dive watch, more than normal watches. I have laid out everything you need to know about a dive watch.

Water Resistance Rating

The water resistance of a dive watch is obviously one of the most important components of a dive watch. The water resistance rating is going to be printed on the dial and often added to the caseback as well. In my opinion a true dive watch should be water resistant to 200 Meters or 660 feet.

99.9% of us are never going to go that deep, but seals, o-rings and gaskets degrade over time. With this degradation also comes the loss of ability for the watch to keep water on the outside. I consider a dive watch part of the life supporting equipment just like a scuba tank or regulator. I don’t want my dive watch crapping out on a dive. That would be bad. So I go for a 200M dive watch. Any less is not enough, and any more is overkill in my opinion.

I have a full blog post detailing water resistance ratings and the ISO 6425 parameters as well as the Diver’s mark and what that means.

If you are interested in that you should click here to read the blog post.

Unidirectional Rotating Bezel

When you look at a dive watch, one of the first things you will notice is the bezel surrounding the outside of the crystal. This is one of the main features that distinguishes a dive watch from other more mortal watches. The bezel is actually a timing device used to time a dive while on SCUBA.

If you try to rotate the bezel it should only rotate to the left. If it rotates both ways it is only for show and not a dive watch. True dive watches only have bezels that rotate to the left, it is called a unidirectional rotating bezel.

I have an entire blog post on how to operate a bezel on a dive watch. To read that post click here.

Bezel Insert

The bezel insert is the piece of material inside of the bezel.

There are three main materials bezel inserts are made from: ceramic, aluminum, and in the case of Omega – liquid metal.

Aluminum is the most common and oldest type of bezel insert. The markings are painted onto the surface of the aluminum. It is essentially a ring of aluminum with paint applied to it, then it is usually baked on to increase durability.

Ceramic is a more recent advent in materials. It has the benefit of being more scratch resistant, and in my opinion looks better. The drawback of ceramic is it is more brittle. Whereas if the aluminum bezel has an impact it might experience  a deformity in the metal, the ceramic insert could shatter.

In the case of Omega, they have invented a new technology called Liquid Metal. In the process Omega bonds ceramic with a metal alloy. According to Omega after this cools it is three times as hard as stainless steel.

I don’t currently own an Omega watch, but I have seen and handled the liquid metal bezel, it is nice. It’s on the wish list for sure.

On many bezel inserts there is a small circle usually filled with lume at the zero marker, this is called the bezel pip. It is luminous so you can set the zero marker to the minute hand during night dives.

Movement

A watch movement, also known as a calibre, is the motor that makes the watch and its complications work. This is really the heart of the watch.

A complication is something additional besides the hands, like a day or date function. There are other complications in watches, such as a moonphase feature, but the day and date functions are the most common in dive watches. Some dive watches also feature a chronograph complication.

In 2019 when I am writing this, there are basically two types of movements in dive watches, quartz and automatic. There are purely mechanical watches that require winding, but these are generally not something you will see in the way of a dive watch, or at least I haven’t come across any of them.

Automatic Movement

An automatic watch is purely mechanical and is self winding, thus it is automatic. There are no batteries inside of the watch, and it can keep going for years without any winding whatsoever. There are gears inside of the watch that turn the hands and power the complications. These gears are turned by a spring called the mainspring.

The mainspring is constantly winding down driving the gears so it needs to be rewound. The way the mainspring gets rewound is from an oscillating weight that swings on a pivot. The weight moves around from the person wearing the watch. As you raise your arm to drink a beer or eat a taco the weight moves around inside of the watch and winds the main spring. If you stop drinking beer and eating tacos you stop winding the mainspring, so don’t stop.

The mainspring does have a power reserve, and depending on the watchmaker it may be longer or shorter, but most of them have a reserve of around one or two days.

Many automatic watches have a hand winding feature, so if the watch stops because you didn’t wear it for a week it allows you to wind the spring to start working. It is recommended to wind it 20 or 30 turns to wind the mainspring.

Are they accurate? Yes, they are very accurate. Most automatic watches lose or gain a few seconds a day. However, there are very high end automatic movements that have even better accuracy.

Automatic watches do need servicing from time to time, usually every five years or so but it depends on the watchmaker. Like a truck engine, they have moving parts that have wear. They do require a little oil on the gears. So it’s best to find out what service interval your watch requires and have it serviced on that schedule. Kind of like changing the oil in your truck.

Quartz Movement

Quartz movements are battery operated electronic movements. They work by sending an electronic current through a quartz crystal. This vibrates and drives the hands and complications. Quartz movements are highly accurate. Some gain or lose a few seconds per year.

The battery usually needs to be replaced every two to four years.

Currently in 2019 many quartz watches are charged by solar power. This was invented by Citizen in 1976. There is a solar cell under the dial that generates electricity and recharges the battery. The benefit is this is a watch that can go years without service or battery changes. Citizen claims that their solar watch can last six months in the dark, and if it does run out just put it in the sun to recharge it.

This is a great feature in a dive watch, because there is potential for mishap every time the caseback is opened to replace a battery of for service. According to Citizen the battery will maintain an 80% rate of charge after 20 years. I’ll let you know when I get to that point with my solar watch.

Overall, automatic movements are more desirable to watch enthusiasts or collectors. An automatic watch is really a feat of mechanical engineering and a work of art. Don’t let this convince you that you need to own an automatic watch. I personally own both quartz and automatic dive watches and I like my quartz watches just as much as my autos. I have a solar quartz movement that I have had for years with no problems. Buy what you like.

Case

If the movement is the heart of the watch, the case is the body.

The case is the part of the watch all of the components fit into. Dive watch cases come in a variety of materials, the most common is 316 stainless steel. This type of stainless steel is highly anti corrosive, durable, and can be very beautiful if polished and brushed.

Other types of materials used for dive watches are gold, bronze and titanium. All of these materials have their pros and cons.

The case of the watch is really the part of the watch that gives it a large part of its styling. Some of the surfaces will be polished while others will be brushed. Some have soft curvy lines while others are more angular. The beauty is definitely in the eye of the beholder.

All of the aforementioned materials are suitable for a dive watch and will withstand pressures far greater than most people will ever place on them.

The case is really the receptacle of all of the other components of the watch. The crown screws into the stem, the crystal is set into the top, the caseback screws into the back and the movement is in the center of it all. The case is the protective armor of the watch.

Case Back

The case back on a dive watch is the access point on the back of the watch that can be opened to change the battery or service the watch. On the vast majority of dive watches this is a screw down case back. There will be an o-ring sitting in a channel that presses between the case back and the case. This will not be visible to the consumer.

Some watches have exhibition case backs that feature a crystal so you can view the movement. This is not common however, and is unnecessary.

Some case backs are ornately detailed with beautiful engravings or reliefs that add to the overall aesthetic of the watch.

Screw Down Crown

First of all, what the heck is a crown? The crown is the knob on the side of the watch where you adjust the time. Bam, that was easy.

Wait, there’s more. A lot more.

The crown is the main control device on the watch. There are basically three components of the crown:

  • The crown itself which is the knob
  • The stem, which is what connects the crown to the movement
  • The tube, which the crown screws down onto, and which the stem passes through

On a dive watch specifically there is also an o-ring, more about that later.

If the watch in question has a day or date function you also adjust those with the crown.

Some automatic watches have a hacking and/or hand winding feature. The crown controls this as well.

Hacking is a feature where you can stop the second hand when the crown is pulled out to a certain point. Some people like this feature because they can set the second hand to be very accurate, or even synchronize watches to the exact time within a second.

Hand winding is pretty self explanatory, automatic watches work by winding a spring which actuates the movement. While you are wearing the watch the spring is wound by a pendulum inside the case, the pendulum swings as you move your arm throughout the day and keeps the spring topped up with power. When wound fully most automatic watches have a power reserve of anywhere between 30 to 50 hours. If you haven’t worn the watch in a few days or weeks the spring will have been wound down and the watch will basically be sitting idle. You can hand wind it to put some power in the spring with the hand winding feature.

Now for the important part, somewhere integrated with the stem or on the tube there will be a rubber o-ring. Every watchmaker does this a little differently. An o-ring is a gasket of sorts that is used to keep water out of the watch. O-rings are in all kinds of devices, scuba gear, cars, faucets, boats. O-rings are specifically designed to keep water or fluid in or out of a device.

So to keep water out of your watch the crown needs to be screwed into the stem. The internet is littered with reviews of dive watches that leak. In reality it wasn’t the watches fault, it was operator error of not screwing down the crown before going in the water.

You must screw down the crown for the watch to be water resistant.

Now some crowns and stems are fragile and some are very robust. When it comes to crowns and crown stems, they are not all created equally. I always recommend taking great care to make sure the crown is in alignment with the tube before trying to screw it down to avoid stripping the threads. Screw it in gently until it stops. If you feel something is not right, stop, back it out and try again. Remember, be gentle.

I have personally stripped the threads on a stem of one of my dive watches. I thought I was pretty careful with it at the time but maybe I wasn’t. I can’t say for sure whether it was operator error or a manufacturing defect. I noticed it when it happened and it was able to be repaired, and works fine to this day.

Pushers

On dive watches with a chronograph complication you will notice above and below the crown there are two additional buttons. They are similar but different from the crown itself. These buttons are technically called pushers.

The important thing to note about pushers is for most dive watches you are not supposed to operate them underwater. Be very careful to check your watch manual to be sure, but as a default never operate them while underwater. 

Dial

The dial of any watch is the face or surface of the watch behind the crystal lying under the hands. The dial can really have a lot of different features.

Dials can be made from a variety of colors, materials and textures and will often feature Arabic numbers, roman numerals or bars on the face. They can include minute markers, places for day/date complications and even military time indicators. The amount of features found on the watch dial are too numerous to be listed on this post.

Needless to say, the dial is a large part of what gives a watch its character and design.

The dial can be completely printed as is the case with the Seiko SKX 007 shown below.

Or, some of the parts of the dial can be applied, or affixed with glue, to the dial itself. Look at the indices on the Jacques LeMans watch below, the indices are actually applied.

Many dials feature some components that are applied and some that are printed. Generally the lower the price point the more printing will be on the dial and as you go up in price to luxury watches more of the components on the dial will likely be applied. I’m sure it is much more expensive to apply each specific individual piece to a dial as opposed to printing the entire thing.

Lume

On a dive watch, or any sport watch for that matter, most watchmakers have the ability to make the markers and hands glow in the dark. This is useful in a dive watch because when we go night diving it makes it much easier to tell our elapsed dive time. Even when not night diving this feature is very handy to have. I find it standard on most legitimate dive watches in the marketplace today.

There are a couple of ways for watchmakers to make the markers and hands glow in the dark. The first and most popular is to use luminous paint. It comes in a variety of brands, the most popular are SuperLuminova and Lumibrite. The luminous paint is applied to the markers and hands just like any other paint.

When painting the lume on the dial or hands, manufacturers have a choice of what type of paint they use, and how many layers they paint. Obviously the better product and more layers they use the better the outcome is going to be. A good lume should last at least for a couple of hours.

The way this type of luminous paint works is that it absorbs either sunlight or an artificial light source like a flashlight and it is emitting the light that it has absorbed. It has to be exposed to light to absorb a quantity of it to re-emit.

The other way is to use very small tubes filled with Tritium Gas. Inside the tubes is a coating of phosphor, and tritium gas interacts with the phosphor coating causing it to glow in the dark.

The tritium tubes do not have to absorb light they are always glowing.

What I have found is that the brands that use tritium, Luminox and Isobrite for example stick with tritium for all of their watches and most of the other brands use the luminous paint.

A freshly charged luminous paint is generally brighter than tritium, but tritium never fades as the luminous paint will fade throughout the night.

Bracelet

How you strap the watch to your arm demands some forethought. There a quite a lot of options when it comes to bracelets and straps. There is an entire industry devoted to aftermarket options.

First of all, you want to make sure your spring bars are heavy duty. Some spring bars that come with aftermarket springs and bracelets are pretty flimsy. These could be the only thing separating you from the loss of your watch.

When it comes to dive watches if I can get a nice bracelet with a good clasp that’s’ what I am going to opt for first. I prefer oyster style bracelets, but there are many styles they come in. If the option to purchase the watch with a bracelet or some other type of strap 100% of the time I’m going with the bracelet.

I can always buy an aftermarket strap for any watch. Or, some watchmakers will sell aftermarket straps. They are readily available. The bracelet however is limited, often you cannot find an aftermarket bracelet to fit your watch. Also, watchmakers generally do not sell the bracelets as an aftermarket add on.

The most common styles of bracelets in no particular order are oyster, jubilee, engineers, mesh and round link. Your style and opinion will vary, like most style choices people like one for a particular reason or feeling. They are usually always very robust from a quality watchmaker.  

On a higher end dive watch you may find a diver’s extension. This is going to be part of the clasp, it will have a small folding extension that you can deploy that is going to give you several millimeters of additional length to the bracelet. This is so it will fit over a wetsuit. The only problem with this is they don’t really know how thick the wetsuit is you will be wearing. It doesn’t work for every situation.

Straps for watch come in so many types of materials it is unreasonable to cover them in this already lengthy post. Some common strap materials are rubber, silicone, nylon, leather and sailcloth.

One of the most common straps people use for dive watches is a NATO or ZULU strap. These look like something the military would use, and for good reason. They have their origins in the British military and many militaries the world over still use these straps. They are incredibly strong and durable.

Hands

The hands are obviously one of the most important parts of the watch, it’s how we actually tell the time. I am personally partial to hands that are a bit unique. I like a minute hand that is easily distinguished from the hour hand. They come in so many shapes and designs it is wonderful.

Hands on a dive watch are going to feature luminous paint or tritium tubes. Some have bright yellow or orange trim. I like big bold hands and tend to gravitate towards those.

Crystal

The crystal is the clear glass looking piece over the dial and hands. It is one of the things keeping water out of the watch when you are diving.

There are generally two types of crystals found in dive watches, mineral crystal and sapphire.

A mineral crystal is made of hardened tempered mineral glass. The reason for this is it is not as hard as sapphire. A mineral crystal is the less desirable of the two. On the mohs hardness scale a mineral crystal measures a five.

A sapphire crystal is obviously the more desirable of the two. All watch crystals are synthetic sapphire, which is expensive to make because it is so hard. It is made into a cylinder and cut with diamond saws and then polished. On the mohs scale it measures a nine, the only thing harder on the mohs scale is a diamond.

Obviously a sapphire crystal is going to be a lot harder to scratch or chip than the mineral crystal.

There is a third type of crystal produced by Seiko. The only reason I bring it up is that Seiko dive watches are pretty popular and many of them include this type of crystal. It is called Mineral Hardlex. It is proprietary and only used by Seiko. The hardness of this crystal falls somewhere in-between mineral crystal and sapphire.

Finally, although the sapphire crystal is harder and considerably more scratch resistant than a mineral crystal, a mineral crystal is still very hard and difficult to scratch. The sapphire crystal is more brittle than the mineral crystal, thus the mineral crystal is harder to shatter than sapphire. I still prefer the sapphire, but this is interesting to not.

Anti Reflective Coating

Although sapphire crystals are harder than mineral crystals, they are also more reflective. So this presents a problem for the watchmaker. You don’t want the watch crystal to be reflecting light so the user cannot see through it to tell the time. It defeats the entire point of wearing a watch.

So the watchmaker can apply an anti reflective coating or AR coating to the crystal. These can go both on the outside and inside of the crystal, but if it is placed on the outside it can get scratched, because it is not very hard. So that kind of defeats the purpose of having a sapphire crystal. A lot of watchmakers only coat the inside and leave it at that.

Helium Escape Valve

Yes, this is not a typo. Some dive watches have a helium escape valve. You might wonder why divers are putting helium in their watches and how much we’ve had to drink to think up such an absurd idea.

99.99% of divers, including me, will never have helium in their watches to worry about. Those that do didn’t put it there on purpose.

The way helium gets into a dive watch is saturation divers live in a diving bell for periods of time when they are working at very deep depths. Because they are so deep below the surface an inert gas needs to be added to the regular air to decrease the amount of oxygen so they don’t get oxygen toxicity.

More simply put, they add helium to the air so they don’t die.

Helium, because its molecules are so small gets into the watch crevices and inside the sealed case. When the divers are being brought up to the surface they need a way to let the helium escape. This is where the escape valve comes in.

If they don’t let the helium escape the crystal will pop out of the watch.

When the US Navy was getting Rolex to build a watch for them for saturation divers to use the crystals were popping off of the watches when they were ascending from depth in the dive bell because the helium gas was expanding. How cool would it be to have been issued a Rolex as part of your Navy gear? That is until the crystal popped out. Rolex eventually solved the problem with the helium escape valve.

Modifications

Modifications or mods are ways to customize your watch. The most common is to change the bracelet or strap. This can give it a completely different look.

Other common mods are changing the crystal, hands and even the movement. The list of mods people have made to their watches is nearly endless. Components are sold in the marketplace and many people take them to be installed at a watchmaker, or even do it themselves.

If there is anything I’ve left out or you feel needs more attention please drop me a line on my contact form.

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