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Loose sub-dial hands Seiko 7A38

Pip

By Pip
in Watch Repairs Help & Advice

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Pip WRT Addict

Pip

Posted
Posted

Hi all,

I've had lots of 7A28's and 7A38's apart before but not had this issue previously - two of the hands just do not seem to bind at all with the sub-dial posts. I can fit them, press them so they are sitting reasonably low to the dial, then just lift them off with tweezers. So far as I can tell nobody has been in this movement before and they seemed ok when I was given the watch. I've only had them off twice so I'm surprised they won't reinstall. I'm sure the 3 sub-hands are all identical but I'll have a good look under the microscope in a minute.  I was wondering if the calendar ring was getting in the way but I don't think it is (sitting nice and central and evenly viewable through each of the 3 sub dial holes, there's nowhere else for it to go).

Any ideas? Is it me mishandling them? I can see from the first pic below that the one on the right is slightly chewed, not bad enough for this though?

Thanks in advance.

Pip.

Pics of top and bottom below and pic of the bottom sub-dial (running seconds) pivot? stem? post? Not actually sure what that bit is properly referred to as.

27750887449_6010964000_z_d.jpg  39496956072_5dcef8448a_z_d.jpg

27750979029_86659223c7_z_d.jpg  39497082702_b203a2592e_z_d.jpg

wolfwatchwerks Member

wolfwatchwerks

Posted
Posted

....you could try some type of hole closing tool. Also a quick non intrusive fix: get a loupe, stretch a thin layer of rodico over the hole with your tweezers. (you will not be able to see the rodico with the naked eye) place over the pivot and seat. This will hold the hand on and work as a temporary fix until more permanent repairs can be made.

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rogart63 Distinguished Member

rogart63

Posted
Posted (edited)

The left one looks a little damaged . Pressed them to far down?  Not you but the tinker that was there before?  Or coming from an other watch?  As they don't look the same on the back? 

Edited by rogart63
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clockboy Distinguished Member

clockboy

Posted
Posted

You could give them a squeeze with a pin vice BUT support the inside with something like a piece of brass wire to avoid an oval shape.

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rogart63 Distinguished Member

rogart63

Posted
Posted

Serviced a 7A28 yesterday. Having trouble setting the sub hands in the right position. Not like a normal 6138/39 where you could press the reset button and the hammer holds it in position . Get it right and then press it down it twist a little. And i have to take it off again and again to get it as perfect as i can. That could be a part of the problem? Lots of on and of can wear it out. 

Pip WRT Addict

Pip

Posted
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Posted

I’ve had a bit of on/off with previous services. These have been off once and after I put them on one fell off and one was loose! Might have been someone else’s efforts a long time ago, this was in a drawer for many years (allegedly). It was a complete non runner that I’m fixing up for someone I know. I’m attempting the pin vice later I think.


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Pip WRT Addict

Pip

Posted
  • Author
Posted

Apparently the correct technique is to tighten them up in a watchmakers lathe. Someone is showing me the way to do this next week, wish me luck!


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rodabod Distinguished Member

rodabod

Posted
Posted (edited)

I find the best way to tighten hand collets is to use a jewelling press. Works for me every time and is extremely precise.

Edited by rodabod
jdm Distinguished Member

jdm

Posted
Posted
1 hour ago, rodabod said:

I find the best way to tighten hand collets is to use a jewelling press. Works for me every time and is extremely precise.

Like a Seitz? How do you do that?

rodabod Distinguished Member

rodabod

Posted
Posted
18 minutes ago, jdm said:

Like a Seitz? How do you do that?

You use a cup-shaped plunger with a larger inner circumference than the collet. You then lower the plunger onto the collet with light pressure and raise the micrometer gauge back until it meets resistance against the plunger. Now drop the micrometer gauge 5/100 at a time and press until the collet is a snug fit. Where possible, you repeatedly measure the hand collet on a hand gauge to confirm you’ve reached the correct size. 

I’ve tried things like using a pin vice in the past, and it can crush the collet out of round and is a bit unpredictable. 

jdm Distinguished Member

jdm

Posted
Posted
5 minutes ago, rodabod said:

You use a cup-shaped plunger with a larger inner circumference than the collet.

You mean, tool ID larger than collet ID (and smaller than collet OD) ?

rodabod Distinguished Member

rodabod

Posted
Posted

The plunger ID has to be larger than the collet OD. You have to go through the plungers until you find a snug fit which allows the plunger to just cover the collet. 

 

jdm Distinguished Member

jdm

Posted
Posted
4 minutes ago, rodabod said:

The plunger ID has to be larger than the collet OD.

How can tighten the collet if it's larger?

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