Seiko 8306-8020

I thought I’d feature todays watch because you don’t see too many calibre 8306’s around, this one is in truly fantastic condition and it’s a front loader so I thought I’d explain the different methods available for crystal removal. This watch is branded ‘Business-A’ which was a Seiko JDM marketing campaign in the 60’s and early 70’s to try and make young Japanese businessmen think their life in the cut and thrust world of commerce would only be complete with one of these branded timepieces strapped to their wrist!

Seiko 8306-8020

As can be seen from the back this has a production date of June 1967, but also of interest to saddos like me is the split 8306/46 reference and the ‘One Piece Case’ script. The 8306 is identical to the 8346 apart from the jewel count, the 8306 has 30 jewels, the 8346 27. If this watch didn’t have a ‘One Piece Case’ I would imagine the casebacks would have individual references but as a case is a lot more expensive than a caseback a bit of rationalisation was called for.

Seiko 8306-8020

There are three usual ways of removing a pressed in crystal from a front loader, the first if the watch has a split stem is to use a case pump, you can buy these and they look like a small bicycle tyre pump, however I prefer to use a syringe and a sheet of polythene! You remove the stem by pulling it out of the tube, place the polythene sheet over the tube to and pierce a small hole in it the place the syringe over the tube and pump. In theory the crystal will pop off with the increased pressure in the case. This system does work but I’m not a fan as to an extent it’s uncontrolled and watch repairers don’t like uncontrolled. However certain watches can only be opened with a pump so it’s used in these instances.

Seiko 8306-8020

The next two methods utilise different types of crystal clamps, one is a traditional crystal ‘claw’ that can be tightened onto the crystals circumference to grip and compress it slightly. The claw can then be pulled to remove the crystal from the case but the disadvantage of this type is you risk marking the crystal with the individual claws if it slips. The final type, and my preferred method, is to use a circular crystal clamp. This has varying sizes of crystal adapters that fit into the holder.

Seiko 8306-8020

Once the watches bezel is removed you select the correct sized adapter to fit the crystal, place it into the holder and fit it over the crystal. Gently squeeze the grip to compress the crystal slightly….

Seiko 8306-8020

….twist and pull at the same time and the crystal will slide out of the case in a controlled and steady fashion. No damage, no scratches, no marking – lovely jubbly.

Seiko 8306-8020

Once the crystal’s out you can see why a pump cant be used on this type of watch, the stem has to be released by pressing the button by the two o’clock marker as it doesn’t have a split stem. Before you do this the case locking circlip has to be rotated to allow the movement to drop out.

Seiko 8306-8020

Here’s a better view of the circlip in the unlocked position, note that split reference again!

Seiko 8306-8020

This has such a pristine sunburst type dial, it’s hard to believe it’s almost 50 years old.

Seiko 8306-8020

With the dial removed you can see the day/date discs, note the day disk only has seven positions and as such only has one language. The advantage of this is it changes over pretty much at the same time as the date so there’s no delay until the correct day appears like there is with the twin language discs.

Seiko 8306-8020

Under the day disk you can see that the day/date changeover fingers are opposite each other to facilitate the synchronised day/date changeover.

Seiko 8306-8020

With the movement turned over the rotor can now be removed to allow the case to be held in a clamp.

Seiko 8306-8020

I then turned it over again to continue the dial side strip.

Seiko 8306-8020

I’d removed all the calendar components by now, just the keyless work to go.

Seiko 8306-8020

And there we have it, a bare plate, jewel caps and canon pinion removed.

Seiko 8306-8020

I could now turn the watch over again and start on the motion work. As this has a hand winding facility you can see the upper crown pinion wheel in this shot. Also, the autowind work is more like a swiss watch than a typical Seiko.

Seiko 8306-8020

The first thing I do is remove the balance and put it out of harms way, especially as the autowind mechanism is situated right next to it.

Seiko 8306-8020

A bit further in and the reverser mechanism can be removed.

Seiko 8306-8020

The train bridge is removed in this shot, not much more to remove now….

Seiko 8306-8020

….and then the watch was fully stripped ready for cleaning and inspection.

Seiko 8306-8020

Seiko 8306-8020

After cleaning no problems or issues were found so the rebuild started with the mainspring as usual.

Seiko 8306-8020

The train is coming together in this shot, ready for the bridge to be fitted now.

Seiko 8306-8020

The bridge is fitted now, part of the difference in jewel count between this and the 8346 is due to the dust covers on the fourth and escape wheel. These are known as diafix jewels and are supposed to offer some shock protection but in reality as there’s no chaton to move and absorb any shock it’s purely there to keep the dust out.

Seiko 8306-8020

The balance is fitted and the power wound on here which meant I could then roughly time and adjust the movement.

Seiko 8306-8020

The autowind mechanism is refitted here. A word of warning about lubrication at this point, with Swiss watches (I’m referring to ETA here) the reverser wheel lubrication is critical, use the wrong stuff and it will cause you no end of problems very quickly. To this end I use a product called Lubeta v105 which is specifically designed for the lubrication of ETA reverser wheels. As the 8306 has a reverser wheel I lubricated it using Lubeta v105 and thought no more of it. After two days on test the watch stopped! On inspection nothing looked wrong with the autowind but when the rotor was spun it wouldn’t wind the barrel. I took the reverser back out, cleaned it again, lubricated it with synthetic oil this time, replaced it and the problem was solved. Lubeta leaves waxy deposits in the mechanism which is just what an ETA reverser wheel needs but in the Seiko version it actually keeps the fingers from engaging with the internal ratchet. Be warned if you ever service one of these!

Seiko 8306-8020

I turned the watch over again and started on the dial side components, the keyless work is refitted and lubed here.

Seiko 8306-8020

The date disc was next….

Seiko 8306-8020

….then the day disc.

Seiko 8306-8020

This allowed me to refit the dial and hands, did I mention what beautiful condition these are in?

Seiko 8306-8020

Turned over again I could fit the rotor….

Seiko 8306-8020

….then the movement could be recased.

Seiko 8306-8020

The watch came with a replacement crystal to be fitted but it didn’t have a polished tension ring as per the original.

Seiko 8306-8020

To solve this I removed the tension ring from the original crystal and fitted it to the replacement. It wasn’t a straight fit and a certain amount of fettling was involved. These procedures are time eaters, it’s amazing how a seemingly innocuous job like this takes a shed load longer than you imagined it would! Once done this just left the bezel as the final piece to be fitted.

Seiko 8306-8020

Et voilà! Another beautiful Seiko set for a few more years. Excuse the fingerprint on the bezel, it’s to late to retake the shot when you notice it after the watch has been returned 🙂

Seiko 8306-8020

Seiko 8306-8020

Seiko 8306-8020

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