How to fit a domed sapphire crystal (Seiko 6309-7040)

Having seen a number of questions regarding the fitting of new crystals to Seiko divers, I have prepared the following simple guide. From the outset I would like to say that anyone can do this, with a few simple tools, even if their 9-year old son William is watching and has an inexhaustible line of questions.


Start with a clean work area. A sheet of printer paper gives a nice, dust-free work surface. The crystal is a domed sapphire crystal from Harold Ng (Yobokies), the watch is a wonderfully patinaed original vintage Seiko 6309 on a Super Oyster with Yobokies solid end links:



Using a sharp pocketknife, ease the bezel off by pushing the knife under the crystal and twisting gently. The bezel will pop off. Take care not to lose the small steel ratcheting ball.



Tell William to keep quiet. Use a rubber-ball (or other) caseback remover to...remove the caseback:



Press down on the retaining mechanism and remove the crown:



Turn the watch over and gently tip out the movement. Cover the movement with a shot glass:



Get another shot glass, pour a whiskey and tell William to keep quiet. Rummage in your box of tools and find the crystal press:



Remove the crystal retaining ring in the same way you removed the bezel:



Send William out to blow his nose. Crystal retaining ring removed:



Use crystal press to remove crystal. A firm squeeze:



...and it pops right out. Check the condition and orientation of the crystal gasket and wipe it with a smear of silicone grease:



Clean the surrounding area with a Q-tip:



Press the new crystal in with the crystal press, checking that the crystal gasket is not pinched:



Place the crystal retaining ring in position:



...and use the crystal press to snap it home:



Insert the movement and crown, making sure the chapter ring lines up:



Lubricate the caseback with a dab of silicone grease and fit, after which the bezel can be snapped on using the crystal press:



And admire your handiwork, after unlocking the cupboard and letting William out:





Time taken: a little over 10 minutes.

THE VERDICT: it was a pleasure to deal with Yobokies, in the same way it is a pleasure to deal with our other suppliers of Seiko parts. We really need to stop up from time to time and thank our blessings by having suppliers who also are enthusiasts

The crystal is a wonderful upgrade to the flat Seiko original. The gentle dome gives depth to the dial and creates a wonderfull play when moving the watch. The dome gives life to the watch and makes it look like it is under water, even when it is not. The AR coating on the inside of the watch gives fascinating blue reflections (see last picture) and makes the dial easy to read at all angles. The fact that it is a scratch resistant sapphire gives peace of mind in daily use. In all, a "mod" which improves an already perfect watch. SCORE: 10/10.

SEIKO PROFESSIONAL 300M Diver, unveiling & review

Arrival and impressions

Finally, the great day arrived, as did my 300m Tuna! Thanks to Jau Yuan in Taiwan for a great transaction and a wonderful timepiece! We had just arrived home from an extended weekend in Holland, so I had ample time to change the wave vent rubber strap to a black NATO, and the bezel insert to a 6309 insert (which clicks right in, in case you where wondering) while the missus and kids emptied the car. The "mod" took all of ten minutes locked in the bathroom "Yes, dear, coooming!!" and the old insert is winging its way to its new home in the US. Let me show you some comparative pictures of the "Mod":





First, my two standards, 7T92 chronograph and 6309-7049 150m diver.





Size comparison of 7T92 on NATO with 300m diver





Strange how the NATO strap fits so perfectly to the “Tuna”, but just doesn’t work (for me) on the 6309. Incidentally, removing the spring bars was an absolute cinch due to the fact that the lugs are drilled through – brilliant! A quick look at the back cover and the documentation revealed that this watch was produced June 2007 and purchased in November 2007! Wow – another five years to the next battery change! First impressions after wearing the “modded” Tuna for an hour are that it is easily as wearable and comfortable as the 6309. The domed crystal is very reflective, and distorts the view of the dial and hands significantly when viewed from the size, fittingly reminiscent of the domed portholes of a bathysphere.





Size comparison of 150m vintage diver with 300m diver





Size comparison of 150m vintage diver with 300m diver





Size comparison of 150m vintage diver with 300m diver



Dial layout and especially hands are comfortingly similar to my 6309 – the hands, descencant from the 6309 divers are simply superb, and this series of hands are in my opinion the best dive hands ever developed! I noticed the lume is slightly creamy and very neatly applied! The crown screws in and out smoothly and competently, while the rough edging makes it easy to grip. The bezel on the other hand is a little difficult to grip and turn due to the shroud, but ratchets nicely once turning. I was also a little surprised to see the taper on the shroud, from base to top – I thought the Tunas where called so because of their non-tapering, grey shrouds?



The SBBN007is part of the Prospex series designed for professional and saturation divers. Ikuo Tokunaga was the chief designer of the original Professional Divers, and has contributed in no small way to forums such as the SCWF – a real privilege for Seiko fans and an honour quite exceptional in the watch world. The SBBN007 makes no compromise to fashion, and encompasses all that I look for in a tool watch: function, legibility and robustness. A little detail I wondered about was the presence of the day/date on a pro-dive watch, until I read about how long saturation divers spend under water…



The SBBN007 is a direct descendant (introduced in 1986) of the vintage Seiko 7549-7010, introduced in 1978: “The first professional quartz diver's watch model of 300m saturation diving specification in Japan. The movement is [7549] caliber which has 5years battery life. There are 17 new technologies, such as L shaped glass gasket structure, glass screw ring fixing structure, twin side shield crown structure, special elastic strap made from polyurethane rubber same as 600m professional diver's watch [*from Tokunaga-san’s watch museum website*]. Compared to the original 7549 300m quartz diver, I prefer the black bezel, fine-knurled crown and slightly sleeker shroud of the original. However, I prefer the dial of the SBBN007 and as stated above my first mod was to exchange the steel bezel insert for a black insert from a 6309 diver allowing me to enjoy the best of both worlds!







So, enough with the emotional stuff - lets move on to some hard facts:



300M water resistance with a screw-down crown and screw-down back, saturation-qualified

The “He-GAS DIVERS 300m” on the caseback has relevance for saturation diving, where deep divers work at depths greatly exceeding the normal dive depth of about 130 feet. These divers work and live under extreme pressure for weeks at a time, under conditions where helium (a small-moleculed gas) in the air can seep past the seals of a watch. If this excess pressure is not released under decompression, the crystal can blow out. Omega and Rolex address this problem using release valves; Seiko solves the problem using its innovative L-shaped crystal gasket.



Dimensions: 43mm (without the crown) Thickness: 14.3mm Weight: 116g



Strap: Rubber Wave Vent Daloaz Z-22 (lug width: 22mm)

The Original Seiko Wave Vent Daloaz Z-22 strap is apparently specially made for the Prospex divers, and is made from polyurethane rubber. The vents allow the strap to “give” while diving, retaining tension on the arm under pressure and eliminating the risk for the watch to become loose on the arm and move out of the line of sight. Aesthetically I prefer the simpler straight vent Z-22 of the 6309-divers, but have seen pictures of the SBBN007 on a black Nato which looked particularly good.





Wrist shot on 19 centimeters = 7.5 inches wrist



Crystal: Dual curved Hardlex

The Hardlex crystal is a Seiko innovation: harder than regular mineral glass, more shatter resistant than sapphire. Apparently, there are at least two grades of standard Hardlex as well as a high-quality HARDLEX "used for the PROSPEX watches and ordinary sports watches" (Tokunaga-san, SCWF, 2002). The extremely domed crystal can give rise to excessive reflections, but under water viewability is excellent.



Lumibrite luminous paint at hands and marks

The lume used in the SBBN007 (and my IWW’d 6309-7049) is Seiko’s own Lumibrite, generally acknowledged to be the best non-radioactive lume on the market – as evidenced by the fact that it is used by Swiss manufacturers such as Omega, under the name Superluminova. According to the manual, if exposed to a light of more than 500 lux (average room luminance), for approximately 10 minutes, LumiBrite can emit light for 5 to 8 hours. While I find the luminescence lasts all night, I particularly appreciate it under the low light conditions we have in northern Europe at this time of year, which saves me a lot of squinting to read the time



But…its just a Quartz!

Ah yes, but WHAT a quartz, WHAT a pedigree! Movement: Quartz 7C46. 5-year long life battery (SEIKO SR43SW) Frequency of crystal oscillator: 32,768 Hz (Hz = Hertz … Cycles per second … my 6309-7059 runs at 5Hz ) Accuracy: +- 15sec/month.







The in-house, 7-jewelled 7C46 movement is a high-end, adjustable, high torque quartz movement used in this the 300m diver as well as the 600M Quartz Prof. Diver (7C46-6009) and the 7c46-7009 Professional Diver's 1000m. The pedigree here speaks volumes about the movements quality. Cheaper quartz movements may have a single (or no) jewels and no possibility of regulation. Irrespective of the WIS attitude to the “soul” (or not) of quartz watches, they are more accurate and stable than mechanical watches. The 32,768 Hz oscillation of a quartz watch is considerably more regular than oscillations of the balance wheel of a mechanical watch, and their accuracy is not determined by the wind state of a mainspring. Furthermore, their accuracy is not as affected by shocks, or by the position of the watch, or to mechanical failures (due to their paucity of moving parts – all factors making them ideally suited as tool watches. However, quartz movements are inherently sensitive to moisture, an argument which has been used to promote mechanical movements in dive watches. Whatever, I have quartz and mechanical movements in my collection, each of which gives me the opportunity to tell about their virtues, their specifications and their developement.



In summary...

All in all the 300m diver lives up to my expectations. With the bezel mod I feel I have brought my watch a step closer to its historic legacy. I appreciate the quartz accuracy and the fact that it is ready to go as soon as I pick it up. It is a big watch, but not uncomfortably so. It makes a statement but is easily wearable. The dial and hands are easily readable under all conditions. All in all, a great addition to my tool/dive watch collection and a watch which will be competing actively with my 6309-7049 as my daily wearer. It will be interesting to see if I can differentiate between wearing the 6309 and the Tuna...



Oh, one more (important) thing, she-who-sees-all hasn't realised I have bought another diver - to her they look the same! Actually, this is the most expensive watch i ever bought (my IWW'd 6309-7049 is in the same league, but was picked up as the result of a trade). But it is a nice feeling buying something this nice, being able to collect so much knowledge about it and sharing the experience with others who have the same passion

6306/6309 ramblings...

A few years ago I decided to buy an affordable, classic automatic diver. After weeks of study I identified a watch known and respected by all watch collectors, a watch with classic lines and provenance, with an instantly recognizable style entirely its own – a style capable of withstanding fashion and trends. This watch was the Seiko 6309 diver. Hours spent reading the SCWF archives; Seiko Diver History and the 6309 Buyers Guide lead me to my first deal: a 6309-7049 from Stephen Go. I wore this watch day and night, and found myself looking at the perfection of its hands (unsurpassed in ANY divers watch, in my opinion) the simplicity of the dial and the wonderful functionality of the case. In time, I told myself, this infatuation for the 6309 divers will pass.





"Infatuation for the 6309 divers will pass..."



Pictures of that wonderful case, downloaded from the internet, began to fill my hard-disk, desktop and office wall. I traded a mint 62MAS for a IWW’d 6309-7049, and felt guilty about my good fortune (thanks Mark ). I began to experiment with straps, “NATO”s and bracelets. I always returned to the Z-22. I discovered Tokunaga-sans posts on the SCWF and began to understand the mind behind this perfection. "Please touch your own favorite watch with your kind heart and love for ever." Ikuo Tokunaga. I began to realise the 6309 series had been designed by a genius, and was already perfect. In time, I told myself, this infatuation for the 6309 divers will pass.



I bought a YAO dial and hands and immediately realized I would never use it. I bought a Tuna 300m diver, and realized I would never wear it. I traded the Tuna and received my first 6306 diver (thanks Badrun ), revelling in its rarity. I discovered that after wearing a 6309 every day for two years, looking at my 6309s and my 6306 was just as satisfying as if I had just received them. I completely lost interest in my lifelong grails, the Rolex Sub (so small, so common and yet so expensive) and the Omega Speedmaster (such a pity about the silly tachymeter scale – why did they not make a rotating bezel version for NASA?). Both of these grails have been heavily "hommaged" - an honour not restricted to them only:





"Imitation is the best form of flattery..."



It must be particularly satisfying for Tokunaga-san to see a Swiss watchmaker "hommaging" his design!



In time, I told myself, this infatuation for the 6309 divers will pass. But it hasn’t. So I would like to spend a moment to share some impressions of the 6309-7049 and the 6306-7001 Seiko 150m Dive Watches, using two examples from my collection:





Seiko 6309-7049 (left) and 6306-7001 (right).



Table 1: 6306/6309 specifications.





For me, the bidirectional bezel is an absolute plus. I use the bezel every day, to mark start points in time: 6 minutes for the eggs, 10 minutes for the lab centrifuge, so my son can track if it is 6pm yet (could be arrival time on a long car trip, or the start of his favourite TV show). So I save a lot of anticlockwise turning by being able to turn clockwise, too! And, lets face it, the "vintage diver" experience is not complete without a bidirectional bezel - after all, how much more exclusive can you get, knowing 99% of the dive watches out there are unidirectional Note added: the 6306 series was apparently also sold outside Japan, specifically the Phillipines (thanks Janice&Fred).



Notice the weight (mass) of each watch. The 6306 is significantly lighter. Perhaps it has been polished and brushed so much it has lost a lot of case material. Or maybe the case design is different to the 6309? Perhaps someone who has both models on the same strap would be so kind as to verify that there is in fact a weight difference? The differences in case design may be marginal, but they are there:





Crown comparison. 6306 at right.





Case comparison. 6306 at bottom.



Notice the differences in the shoulders of the lugs - they are higher on the 6306. Note added: the weight difference and shoulder sugges that my 6306 case has been heavily altered. Earlier 6306 cases had a significantly larger crown cut-out, but in my examples the cut-outs appear about the same. Buts lets dwell on the genius of the case for a minute. The crown protection offered by the case is perhaps the most elegant, the simplest and the most innovative ever conceived. It’s what makes the 6309/6 series instantly identifiable, a true trademark design element. Notice also how the planes of the case mould into the arm and the back of the hand. This is the reason why the 6309/6s are as comfortable in use, as wearable as a dress watch in spite of their heft and presence:





"The planes of the case mould into the arm and the back of the hand..."



Comparing these two watches is also a comparison of two (almost) identical straps. On the 6309: a Chinese Z-22; on the 6306 a Japanese 6306. The Chinese strap is stiffer, and retains its "bend" in the picture below. The holes in the strap are larger, too.





Chinese Z-22 strap (top), Japanese Z-22 (bottom).





Chinese Z-22 strap (top), Japanese Z-22 (bottom).



The Japanese strap is far softer, more pliant, and lies flat. Both are immensely comfortable, and on the wrist I can feel no difference. Somehow I feel like the Chinese strap will last longer.





Table 2: 6306/6309 beat rates.





I often see technical reviews with lists of data, which at first glance seem dry and uninteresting. But many of these numbers are capable of telling a fantastic story if we can compare them with something tangible. Take the beat of 21.600 bph. Hmm? Nothing? Now consider the equivalent 6bps - that’s really swinging! Or over half a million single, precise beats of the balance and escapement. A day. And we hear of 6309s being used daily for 20 years without a service. That’s almost 4 thousand million beats. Running at a precision greater than 99%. The mind boggles...



Table 3: 6306/6309 jewel distributions.





As we all know, jewels are included in a watch to reduce friction at the main pivotal points of the watch mechanism. I have tried to identify where they are used in the 6309/6. The first main area of use, in pretty much all jewelled watches, is the Escapement and balance. Let me repeat the numbers: "[...] we hear of 6309s being used daily for 20 years without a service..[.].. almost 4 thousand million beats." The 6306 has replaced an escapement hole jewel with a hole-and-cap (2 jewels) giving improved oiling and potentially a slight increase in performance. Less important from a performance point of view are the Gear Train jewels, increased from 5 to 8 in the 6306 by upping the third wheel to a full complement of 2 jewels (replacing a bushing) and adding a cap to one of them) and replacing the fourth wheel bush with a jewel.



For kicks, I wore both the 6306 and the 6309 for the last week, and recorded their timings. Actually, I had started with recording the 6309's time a few days earlier:



Table 4: Results of 6309 timing study.





Table 5: Results of 6306 timing study.





Table 6: Summary of 6306/6309 timing study.





Of course, rates and amplitudes depend on the condition of each watch. The 6309 had some kid of horological hiccup over the weekend, losing a couple of minutes, but seemed to recover. I stopped the test today and will repeat it next week with each watch on the winder for a week at a time.








So there we have a comparison of the 6309 vs 6306 third generation Seiko Diver watches. So similar yet so different.



In time, this infatuation for the 6309 divers will pass. Just not for me...

How to fit a domed sapphire crystal (Seiko 6309-7040)

Having seen a number of questions regarding the fitting of new crystals to Seiko divers, I have prepared the following simple guide. From the outset I would like to say that anyone can do this, with a few simple tools, even if their 9-year old son William is watching and has an inexhaustible line of questions.

Start with a clean work area. A sheet of printer paper gives a nice, dust-free work surface. The crystal is a domed sapphire crystal from Harold Ng (Yobokies), the watch is a wonderfully patinaed original vintage Seiko 6309 on a Super Oyster with Yobokies solid end links:



Using a sharp pocketknife, ease the bezel off by pushing the knife under the crystal and twisting gently. The bezel will pop off. Take care not to lose the small steel ratcheting ball.



Tell William to keep quiet. Use a rubber-ball (or other) caseback remover to...remove the caseback:



Press down on the retaining mechanism and remove the crown:



Turn the watch over and gently tip out the movement. Cover the movement with a shot glass:



Get another shot glass, pour a whiskey and tell William to keep quiet. Rummage in your box of tools and find the crystal press:



Remove the crystal retaining ring in the same way you removed the bezel:



Send William out to blow his nose. Crystal retaining ring removed:



Use crystal press to remove crystal. A firm squeeze:



...and it pops right out. Check the condition and orientation of the crystal gasket and wipe it with a smear of silicone grease:



Clean the surrounding area with a Q-tip:



Press the new crystal in with the crystal press, checking that the crystal gasket is not pinched:



Place the crystal retaining ring in position:



...and use the crystal press to snap it home:



Insert the movement and crown, making sure the chapter ring lines up:



Lubricate the caseback with a dab of silicone grease and fit, after which the bezel can be snapped on using the crystal press:



And admire your handiwork, after unlocking the cupboard and letting William out:





Time taken: a little over 10 minutes.

THE VERDICT: it was a pleasure to deal with Yobokies, in the same way it is a pleasure to deal with our other suppliers of Seiko parts. We really need to stop from time to time and thank our blessings by having suppliers who also are enthusiasts.

The crystal is a wonderful upgrade to the flat Seiko original. The gentle dome gives depth to the dial and creates a wonderful play when moving the watch. The dome gives life to the watch and makes it look like it is under water, even when it is not. The AR coating on the inside of the watch gives fascinating blue reflections (see last picture) and makes the dial easy to read at all angles. The fact that it is a scratch resistant sapphire gives peace of mind in daily use. In all, a "mod" which improves an already perfect watch. SCORE: 10/10.