Not really much to say about this, everyone knows they are the holy grail of Seiko dive watches, and this 62MAS does not disappoint. Great condition and the drama of a worn barrel bushing make for an exciting tear down and rebuild.
Movement in the case.
Automatic work removed. We can see dried up oil on the seconds wheel pivot/bushing and a very old case-back gasket.
Dial and hands removed.
We can see the calendar work.
The movement side. With the ratchet wheel removed we can see a lot of old oil and metal particles seen on the top of the barrel bridge near the hole for the arbor.
Barrel/ train bridge removed exposing gear train and barrel.
We can see the oil has turned into a grinding paste and worn the hole for the arbor oval. This will cause the ratchet wheel to rub on the bridge and the barrel to foul the seconds wheel, resulting in a big amplitude drop and timing issues. It needs to be properly addressed.
To the lathe we go! For more abundant calibers like the 61xx series movement's we install jewels that are made to fit, however, we don't see enough 62MAS's come through the workshop to install jewels. In this case we drill out the bridge and make a bushing. First, we need to centre the bridge with the microscope.
Next, we ream out to size.
Here we can see the bridge ready to receive the bushing.
We use a stock bushing with a smaller inner diameter, then ream to the interior size using the same method. Centring with the lathe and reaming.
Here we have the completed bushing, reamed to final size.
The repaired bridge.
Now we test fit to make sure everything went to plan. The barrel is upright and we have even spacing on both sides of the bridge. If our drilling was off centre, that would be seen here. The barrel would be lopsided.
Next, we check centre wheel and barrel engagement - looks good.
Last step is to remove the mainspring for cleaning and then into the cleaner the movement goes.
While we wait for the movement to clean, we can start rebuilding the crown. The crown gasket used in these and the 6105-8xxx series watches tend to become rock hard over time and it makes it very difficult to set the time, and they also lack water resistance. We have gaskets made to OG specs that we use to make time-setting easier and get them water resistant once again. We can generally make 90% of all vintage Seiko's that come through the workshop pass a water resistance test. The crown pictured below, with stem removed.
Next, we open the crown up and remove the old gasket. Opening the crown is a tedious process so as to not to damage it. I see a lot of crowns with damaged washers as people try to dig them out with a screwdriver - very ugly stuff. You can see the old gasket is cracked and rock hard - the new, blue gasket on the right.
Installed in the crown. Note the tight fit - all the way to the edge of the crown.
Closed up again and ready for water testing.
With the cleaning cycle complete we can get to assembly and lubrication.
The mainspring has been cleaned, lubricated and wound back into the barrel. The barrel and gear train are installed.
Barrel/train bridge, ratchet wheel and pallet fork in place.
Finally, the calendar side assembled. We also needed to replace the setting lever spring as it had worn and wasn't giving a nice 'click' when pulled out.
Dial and hands installed. What a beauty.
Freshly serviced and repaired movement in the case.
The final product. The watch was then pressure tested for water resistance and passed with all new gaskets installed. Next up, final testing.