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· Premium Member
6,103 Posts
I've never done a chrono myself, but from what I understand installing the hour and minute hands are the same, the extra register hands are pretty straight forward. The issue is with the main sweep hand that does double duty as a second hand. As I understand it the mounting process for that on 6138's and 6139's is a little different than on a regular caliber and not quite as straight forward.

Maybe someone else who has done it can chime in with the exact difference.

· Registered
183 Posts
Its kind of a little more complicated.

Its not that easy... there is a little more to do.
and its quite easy to crush or bend both the sweep tube or register hands.

I asked someone- who kindly explained the way the Seiko manual suggests, and its the same way I watch my watch maker do it.
and the way I did it.
Im a hack but maybe someone who does this all the time can jump in and fix what I may get wrong here.
maybe someone who moderates the repair section of this very forum can help???

his intials are KS.

Ive done it a few times, and did Ok.
But I also broke a bunch of crap before I did ok.

You need to get the watch out of the case first, and its just a little more too it then a non complicated movement.

Open and or remove the bracelet or strap clasp/deployant its easier that way.
Take off the case back like any other watch. The chrono buttons make it a little more involved.
there is a button to release the crown just like the 6309 but you will need to depress the pushers in at the same time, then you can take the movement out.
You might want to take off the bezel and crystal- while your there now, more on that later.

Most of the diver hands are quite large and robust by comparison so bear that in mind.
taking the hour and minute hands off is very easy- but the sweep hand is often very firmly in place and sometimes is difficult to reset, the 'tube' on the sweep is delicate, more so then a seconds hand. You can use a hand puller, I have been using tooth picks and even coffee straws allot and do ok with them after some practice.
If you are using cheap hand pullers you need to mask the dial.

Or enjoy your new scratched dial

You need to set the hands to 12 and the register to zero so that the date will change correct and the chrono register hand will be easier to realign.
easier is realitive its not that easy.

to get the register hand off the way Seiko recommends that you loosen the dial feet and invert the Dial and push the register hand or hands of that way.
It makes allot of sense to let the dial do the pushing vs you doing the pulling and probably bending the hand.

Putting the hands back on is different.
the hour and minute hands are easy.
the sweep if you are replacing it usually needs the tip trimmed to fit. If its a legit Seiko part It will be long.
the tube/pinion fit is stiff but unlike a seconds hand it only goes on one way.

The register hands or in your case hand is a pain in the ass, but you can do it with a good does of paitience and trial and error.
Its going to take some time.

Your going to need to put the movement back in to a case to use the pushers and here is why you want the bezel and glass off or a spare case, if thats ever possible.

When you try to set the register hands the axles are going to spin.. you can depress the chrono buttons to reset it to zero and that will get it close.

DONT PUSH THEM ON ALL THE WAY... the hands need to be on enough to not fly off when you press the reset pusher but on loose enough to nudge.

If you put the hand on with appropriate depth, you should be able to nudge the hand to the exact zero position,
But you HAVE to be pressing the reset pusher

If you did not put the hand on enough they will go flying when you depress the pusher,
nice right???
Its going to go a few rounds.
Tooth pics work great here, but Its easy to scratch the dial.
like far to easy.
once you get the hands where you want you can set them all the way.

then you get to un case the movement, reinstall the crystal, and bezel while the movement is out, cause no body really sets the crystals while the movement is in the case right??
then you get to recase the movement ,and enjoy your handiwork.

seems simple enough.
or just bring or mail it to someone who can do that.but heh what do I know

and as a hijack when did all the little smiley guy things get so garish?


· Registered
154 Posts
The main chrono hand, the big one, needs to be re-sized any time its taken off its pipe. These get stretched out a bit when they are removed and they should be squeezed down (re-sized) in a collet so that they go on tight and don't fling off from the shock of being reset.

I wrote a piece on this over on the old forum, but I have`nt been able to find it since (Must be my cockamamie way of tittling posts, LOL)

The short answer is its not as easy as a regular 3 hand watch, not by a long shot. Allot of chron hands are ruined by repairers that don`t know the procedure. One way of getting around this procedure is to use a BRAND NEW main chrono hand when replacing them.

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