It is a truth universally acknowledged, that a Seiko man (or woman) in possession of a good pre-1976 150m divers watch, must be in want of a crown gasket that does not leak.* But let’s face it: anything pre-1976 is pretty ancient and crown gaskets do not age well, gradually losing their suppleness, hardening and eventually cracking. This would not normally be a problem were it not for the fact that the gaskets in the crowns of the 62MAS and both generations of the 6105 are encapsulated, trapped behind a permanently fixed washer, thus rendering the crown a non-serviceable item as far as Seiko were concerned. The technical documents issued at the time recommend replacement of the whole crown when the gasket becomes ineffective.
So, the choice presented to the owner of a leaky Seiko 6217-8001, 6105-8000 or 6105-8110 is somewhat stark: locate an original old stock Seiko replacement crown with a supple gasket ; buy an aftermarket facsimile part from Ebay (if such exist) or find an expert with experience in servicing this non-serviceable part. Option 1 is not to be ruled out entirely as old service stock is still available but more often than not the gaskets have hardened from age (the subject of this post is in fact one such example). For me option 2 is a non-starter: I’d rather have a leaky crown than fit a part of dubious character and so we come to option 3: I’ve seen one or two quite successfully-executed examples of gasket-transplanted crowns and one or two which look somewhat the worse for wear following the experience. The main challenge in conducting this operation is to remove the washer without damaging either the washer or the crown itself or the threaded tube into which the stem fits.
In the example shown below, the washer has been extracted by prising it out but in the process it has been mangled and the outer face of the crown shows a dimple caused most probably by the threaded tube having been bent to one side during the process of levering out the washer.
For years then, this has been the status quo, no one having come up with a neater method for replacing the original gasket. However, back in July, a member of the Seiko and Citizen watch forum and UK-based Seiko parts trader announced that he’d found a way to remove the washer from a 6105 crown without damage. He did not reveal his method at the time but a couple of months later did just that, and I have to say, his method is rather ingenious. As I have a growing collection of useless Seiko 6105 and 62MAS crowns with rock hard gaskets, I thought it about time I give this method a try, but this time on the earlier crown fitted to the 6217-8001 and 6105-8000 watches.
The crown I selected for my first attempt was a NOS crown bought from Yahoo Japan a couple of years back but when I received it, I discovered that the gasket was so hard I could not even get the crown to sit on the pendant tube of the watch I had in mind for it. Here it is, blissfully ignorant of the indignities about to be inflicted upon it.
This view nicely presents the dilemma we are faced with: how do we remove the washer sitting over the gasket without it ending up looking like that of the crown in the opening photo? Any ‘pull me’ approach would seem inevitably to involve leverage and the likely damage to the washer. But what about somehow pushing the washer out from the rear? How could that be accomplished? The proposed method is not completely dissimilar to the approach used to remove crystals from some designs of one piece watch case: a pump is attached to the pendant tube and air pumped in until the interior pressure is sufficient to pop out the crystal. We can’t do that here but we can exert pressure from within through the method of gasket stuffing. The process goes something like this:
Step one: Assemble a small collection of rubber gaskets whose inner diameter clears the inner tube on the crown and whose outer diameter clears the aperture in the washer. Insert the first gasket
and then, using a spot of brute force as required, work the crown onto the pendant tube of any spare watch case whose tube is of the correct diameter. Repeat with a second gasket, and then again with a third and so on until you start to see evidence of doming of the washer.
As I was in the process of servicing another movement at the time (to feature in the post after this one), I took advantage of the opportunity and popped the crown and spacer into the watch cleaning machine with the movement parts for a spruce up.
We now are ready for a fresh gasket of the correct size. Locating such is not as straightforward as would normally be the case because the gasket is not of a common size available from watch materials houses. Seiko do not list the gasket as a separate part either and so I had to measure the old gasket and see if I could locate something suitable. Fortunately, I found a supply of nitrile o-rings of the correct size from a seller on Ebay for a couple of pounds. The new o-ring fits snuggly into its new home.
Aside from the initial extraction, the next most challenging step follows: how to re-seat the washer. In a sense, refitting simply requires the reverse of the removal process: the pressure from the gasket stuffing had domed the washer out to a cone shape and to I thought the best way to refit it without the need to resort to glue, was to shape it into a more symmetric cone shape whose outer diameter was slightly smaller than that described by the lip around the inner edge of the aperture in the crown. To accomplish this I used my staking set with a dome-ended punch combined with a bowl-shaped stump.
Inevitably, as this was my first attempt, the washer did not emerge entirely unscathed, but only marred in a minor cosmetic sense. Here it is sitting back in position ready to be flattened back into position.
The flattening of the washer increases its outer diameter again so that it now sits snuggly and securely once more within the groove in the crown. All that is left is to transplant the stem from the watch to which I wish to fit this particular crown (the ‘basket case’ whose story can be found here).
The proof of the pudding, and the whole point of the exercise after all, is to check that the new crown gasket is capable of providing sufficient water resistance. I decided to take a slightly prudent approach in this case, and removed the movement prior to the test, with the crown then held in position solely by the friction of the new o-ring gasket against the watch case pendant tube. Here is that old 1970 vintage 6105 case, poised above the water level at 6 bar, waiting for a period sufficient for any leaks to equalize the pressure within and without the watch case.
A little while later, the case is lowered into the water and the pressure released. If the watch is leaky, then a return to atmospheric pressure above the water level will result in a stream of bubbles from the now pressurized watch case emerging from any points of weakness. In this case, no such stream emerges, only the odd lazy bubble from air trapped in cavities within the exterior fittings of the case.
Satisfied that this old favourite of mine was now water tight, I dried out the case, refitted the movement together with its new crown, and have been enjoying it again for the past day or two, secure in the knowledge that the odd inadvertent dunk is not going to do it any harm.