Seiko 6138/9 sweep hand issues

Hello everyone! To start with, apologies for the lack of updates over the past few months but it’s been very hectic here on a personal level as well as a business one. Without going into too much detail my parents were involved in quite a serious car crash at the beginning of the summer, my father escaped relatively unscathed but my mother and a passenger weren’t so lucky. Thankfully they’re both back home now but my mother was in hospital for three months and is now having to learn to walk again, which at the age of 80 is going to take some time. As if this wasn’t enough at the beginning of September my partners father suddenly and unexpectedly died, this was a huge shock and taking care of his wife and all the things that a death in the family brings with it has taken some time. I’ve been working seven days a week (when I’ve been home) to try and keep on top of the work queue and things are slowly getting back to normal.

Anyway I thought I’d do a little informational post on something I see on a regular basis and that’s misaligned 6138/9 sweep hands. The bullhead pictured below came in for a movement service but as you can see the sweep hand consistently resets to the 1 second past position which means it’s been fitted incorrectly.

6138-0040

No problem I hear you cry, just remove it and reposition it! Unfortunately with the calibre 6138/9 it’s not as simple as that. The chronograph centre wheel pinion isn’t circular like most pinions, to counteract the g-forces generated during a reset Seiko machined the end into a “D” shape.

6138 chrono centre pinion tip

This means when the hand is pressed on its pipe takes the shape of the end of the pinion, and from then on that hand is matched to that pinion. Try swapping the hand to a different pinion and the chances are it’s not going to end up resetting bang on 12 as every centre wheel’s “D” is in a slightly different position. This makes a job like fitting a new chronograph centre wheel (a component that commonly fails) not so simple as the original hand will no longer reset to 12. Also fitting used hands to replace aftermarket ones are prone to do the same.

The only solution is to try and reshape the hands pipe back to being circular, it sounds a simple job but it’s fraught with problems. The first of these is the age of the hands, I’m not sure if the metal becomes more brittle with the passage of time but what I do know is it’s amazing how many pipes split when they’ve been reshaped and pressed into position of a different pinion. The secret to any adjustment is actually reshaping the pipe, if you don’t have the correct tool then it’s nigh on impossible to do, in the early days I had some success using a pin vice but I think that was more good luck than good judgement! The third is no matter how good the reshaped pipe is the hand always wants to press back on in the position it came off, it takes some force to twist the hand whilst it’s being pressed down to overcome this problem. The tool to use is a collect/hand vice, these are miniature little vices that accept different size collets and are used to tighten hairspring collets or tighten hand pipes.

Collet vice

The 6138 above has obviously had a NOS hand fitted, but it has been fitted badly which is very frustrating.

Seiko 6138-0040

Once the hand is removed it’s placed into the vice with the correct sized collet for the diameter of pipe. Then it’s nipped up gently and slackened off.

6138-0040

The hand is rotated through 90 degrees and the vice is gently tightened again. Slacken it off, turn a bit more, squeeze it up again, rinse and repeat until the pipe is round again.

Seiko 6138-0040

It can take quite some time massage the pipe circular again, the temptation is to tighten the vice too much which eventually will reduce the diameter of the pipe and it won’t go back on the pinion no matter how hard you press! Slow and steady is the order of the day and eventually it will look circular again.

Seiko 6138-0040

The next hurdle is to press the hand back on whilst trying to rotate it against its old position which was one second out. To do this I use the end of a dowel of pegwood, this “grips” the top of the hand a lot more effectively than a nylon hand press and you can exert a surprising amount of sideways force as the hand is pressed home.

Pegwood

If you’re successful then once it’s fully home it should line up at 12 o’clock. I must stress this isn’t always the case and some hands just wont to co-operate and a new one has to be fitted. The problem with that is new old stock hands are a finite resource, I’d much rather re-position an existing hand, it saves my stock and is cheaper for the customer!

Seiko 6138-0040

I tend to do any hand positioning jiggery pokery before I service the movement, once the hand’s sorted the watch is stripped….

Seiko 6138-0040

….and all the usual steps are taken to rebuild it so it’s good for a few more years.

Seiko 6138-0040

Seiko 6138-0040

Seiko 6138-0040

 

Hopefully as things slowly return to normal here the updates will become more frequent again 🙂

3 comments

  1. Great post Duncan, thank you. And I wish your family all the best and hope your Mum is on the road to recovery.

    Excellent job there though, a perfect result. So as you rotate the hand pipe in the vice it just squeezes the pipe gently, and you rotate through all the angles to eventually make it cylindrical? Once you press the hand on with the wood are you then forcing (for want of a better word) the D shape into the pipe, but any slightly retention of the original shape on the hand will simply not allow this to happen, so starting with the best possible hand shape is the only way I guess. Also do the original two part chronograph hands have the same issue?

    Cheers Duncan!

    Guy

    Like

  2. First of all, All the best for your Family and you for this New year.
    Great Post , very interesting I think I’m going to send you some watches for service…
    I’m on IG as ” Bertnet69 ”
    Congratulations.
    Kind Regards
    Bertrand

    Like

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