Seiko 6138-7000 slide rule

I thought I’d feature this 6138-7000 because it’s a variation of Seikos twin register chronograph that isn’t seen very often. It’s unusual in as much as it has a slide rule bezel and indicator much like the contemporary Breitling Navitimers, although quite how pilots were meant to operate it whilst flying a plane I’m not entirely sure! This example came in for a bit of a smarten up and a full movement service.

Seiko 6138-7000 slide rule

The caseback indicates a production date of June 1972.

Seiko 6138-7000 slide rule

Once I’d removed the back I could see the movement was complete and in reasonable shape.

Seiko 6138-7000 slide rule

With the movement uncased the dial and handset appeared to be in cracking condition.

Seiko 6138-7000 slide rule

I soon removed those which revealed the day/date disks, again in good shape.

Seiko 6138-7000 slide rule

With those removed along with the date changeover wheel and a couple of plates the top chronograph plate could be removed.

Seiko 6138-7000 slide rule

This reveals the 12hr register wheel and reset/start levers along with the keyless work.

Seiko 6138-7000 slide rule

With the lever work removed it just leaves the keyless work to go….

Seiko 6138-7000 slide rule

….which didn’t take too long.

Seiko 6138-7000 slide rule

I could then turn the movement over to start on the chronograph/motion work.

Seiko 6138-7000 slide rule

Here the train wheel bridge is ready for removal.

Seiko 6138-7000 slide rule

The stripped components were then sent for a trip through the cleaning machine.

Seiko 6138-7000 slide rule

Seiko 6138-7000 slide rule

Whilst the cleaner was running I turned my attention to the case parts. The watch arrived with a better case and bezel, a NOS crystal and an original plastic indicator ring. These are very difficult to source these days!

Seiko 6138-7000 slide rule

The case, pushers, springs and crown were all ultrasonically cleaned….

Seiko 6138-7000 slide rule

….then new seals were fitted along with the crystal and indicator ring and the case was now ready for the movement.

Seiko 6138-7000 slide rule

After the movement parts were cleaned the inspection turned up a shattered top barrel arbor jewel, this component is critical as the 12hr register is run directly from a wheel located on the arbor, any lateral movement would play havoc with the reset.

Seiko 6138-7000 slide rule

I had an old top plate with a good jewel which I managed to remove without cracking it! This meant the jewel was a direct fit and no adjustment of the plate was necessary. The old jewel was pressed out of the plate with my Seitz tool.

Seiko 6138-7000 slide rule

The old and the replacement compared.

Seiko 6138-7000 slide rule

The jewel was pressed home flush with the plate, again using the Seitz jewelling tool Here is a shot of the old donor plate and the transplanted jewel in place in the new one.

Seiko 6138-7000 slide rule

The jewel in its new home.

Seiko 6138-7000 slide rule

Reassembly could now start beginning with the mainspring.

Seiko 6138-7000 slide rule

The motion work and chronograph layer are ready for the bottom chronograph plate to be fitted in this shot.

Seiko 6138-7000 slide rule

And here the plate, pallets and balance work is all reinstalled. The movement can now be demagnetised and roughly timed.

Seiko 6138-7000 slide rule

On the other side reassembly started with the keyless work….

Seiko 6138-7000 slide rule

….then the 12hr chronograph levers and wheel….

Seiko 6138-7000 slide rule

….the top chronograph plate is next, note the top barrel arbor jewel and its proximity to the hour register pinion.

Seiko 6138-7000 slide rule

The day/date disks were next….

Seiko 6138-7000 slide rule

….followed by the dial and handset.

Seiko 6138-7000 slide rule

The movement was recased then the autowind mechanism and oscillating weight were refitted….

Seiko 6138-7000 slide rule

….which meant my work was done. I have to say this is a cracking example of Seikos little seen twin register chronograph ‘slide rule’.

Seiko 6138-7000 slide rule

Seiko 6138-7000 slide rule

Seiko 6138-7000 slide rule

And a shot with the chronograph running.

Seiko 6138-7000 slide rule

 

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