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Toad's Guide - Repairing Broken Post on Subdial Hand (i.e. Fixing Screw-ups in Hand Removal)

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Hey fellow RWG'ers.  It's been a long time since I posted a guide..and it all started with me deciding to dive back into learning how to work on watches, after a long hiatus from anything technical.

 

If you're going to learn to do something...and are essentially starting from ground zero...why not do it with trying to service a broken A7750? 

 

I originally posted a somewhat stupid question here:  Toad's Stupid Question on A7750 Weirdness

 

The question was NOT stupid because it highlighted weirdness in the a7750 movement with press fit caps, wheels, and shims, but highlights me forgetting that dial hands have inserted posts to hold them on to the counting wheels, and realizing that I had accidentally damaged my subdial hands on removal without noticing when I posted my question.  With this realization in mind, I thought I would post a quick guide on how to fix this problem...in case anybody runs into this problem like me.

 

THE PROBLEM

Even though I used proper tools, I still broke my subdial hands by separating the mounting post from the hands themselves.  How did I not notice this?  Well, as you can see from the picture below, these are SMALL parts:

20191127-213851-1.jpg

This is a sample screw...the post in question is probably half the size of this screw.

 

 

20191128-155049-1.jpg

Broken Post

 

Here is a picture of a hand with the post attached, and one without:

20191128-152659-1.jpg

Top = no post; Bottom = post attached

 

SOLUTION

If you're feeling lucky...you could try and just press the parts together without using the proper tools...but...yeah...good luck with that.  The odds of little pieces going flying or bending things badly is VERY HIGH!!

 

However, if you want to learn to do it properly, and you just happen to be a hoarder and happen to have a staking tool set lying around that you almost forgot about, buried in the basement behind spare electrical parts and drywall tools (no joke) you can do what I'm detailing here.  If you're even luckier, you may know how to use it...or know how to Google (yes, Google is a noun and a verb).

 

PREP WORK:  dust off the tool. and clean it up a little if yours happens to be as dirty as mine.

 

1) Insert broken post, long tube into the anvil base of the staking tool, in the hole that is large enough to receive it, but small enough to catch on the lip of the post

20191201-124330-1.jpg

The observant among you will notice the hole second from the right has the needle tip jammed in it that I broke off trying to clean out the 10 years of grime that filled the holes.  DOH!!

 

2) Select staking punch that will fit over the post but press onto the lip of the separated post

20191201-124804-1.jpg

 

20191201-125019-1.jpg

 

3) Use some Rodico (preferably cleaner than the piece I'm using) and hold the subdial hand in place, with the hole centred over the post

20191201-125246-1.jpg

 

4) Insert the staking punch into the anvil top and align it, centred over the post / subdial hand combination, being careful to ensure everything is lined up

20191201-125310-1.jpg

 

5)  Press down, and voila!!  I have seen some recommendations to either solder, or epoxy the tube to the hand as a backup.  I'm not sure my soldering skills can do that without ruining the subdial hand

20191201-125411-1.jpg

 

And here is the final repaired hand.  Now, if only I could find that other post...then I could repair the other dial hand that got damaged.

Enjoy...and hopefully somebody finds this useful.

 

Toad.

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Dang Toad, that’s a nice write up. Thank you for all the great articles you do here! :notworthy:

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