When a simple job is not so simple

Recently I had a quartz Seamaster in for refinishing, electrical checks, new seals, and of course a new battery. Everything was fine up until I disassembled the HEV - rust:



The seal that was in the HEV cap was toast - thankfully the second seal inside the HEV prevented any water from actually entering the case:



But the real issues started on the case tube side of the case:



You can see that the case tube itself is no longer round, and there are two dents on the crown guards. The crown looked fine, so this tells me that the watch was dropped and the crown was replaced, but whoever did the work left the slightly mangled case tube in place. Not a big deal, as I replace these often. I removed the crystal and heated the case tube:



And removed the tube - it came out unusually easy. Comparing the new and existing tubes, we can see there's a problem:



The old tube is very short, so someone has machined it down in length for some reason - well that reason is that the threads in the case itself are pretty messed up:



Lots of extra glue, and threads that were mashed over - not good as the new tube would barely go in 1 thread after I removed the glue. So, ordered in a set of taps for the case:



There's a starter tap and a finish tap - this is so that the material is removed a little at a time, preventing the tap from breaking inside the case, which would be bad:



So I used the starting tap first - I turned it in only with fingers, to again help prevent the tap breaking - I could feel it cutting:



Then the finishing tap - more cutting:



Fair amount of steel chips coming from this, so I was wondering how much thread would be left, but it turned out great - the threads are nice and sharp again:



Test fit - new tube screws all the way in:



If this didn't work, the only solution was a new case, and that was $1600, so this was a good save.

Sometimes the simple jobs get more complicated really fast, in particular when the person who worked on the watch previously doesn't fix the problems properly.

Cheers, Al

Both very interesting and educational. Thanks for posting, Al.

Always appreciate when you spend your time to educate us. Thanks for this one and all the others.

That would've been more expensive :

https://omegaforums.net/threads/unfortunate-repair-situation.170169/

Always nice to see the lengths a good watchmaker goes to to do things the correct way.

My father was a plastic surgeon. He said the worst part of his work was trying to fix what another surgeon fυcked up.
Glad you were able to save this one and thanks for sharing it,

Could this case have been welded,drilled and then tapped?

Stainless is a not easy to cut, so I think that's one of the main reasons they do this. Of course I was backing the tap out to break the chip at least once per turn in.


Yes, but finding someone who can do this, and reproduce the exact hole location, is way tougher than it sounds. Even just to drill out the soldered case tubes, and drill and tap the case for a threaded case tube, requires some rather elaborate fixturing - I did use this in training at Omega. I specifically asked to do this when I finished on the Friday afternoon, and all the others in class were still doing the watches they were assigned. This is the kit from Omega, which is quite a lot of money - different rings for each case to help center it:



Set-up for drilling here - a specific probe is used to align the existing hole in the case:



Now tapping the hole:



If the hole isn't positioned accurately, it can cause major issues. It has to be spot on regarding the position of the hole on the circumference, while at the same time the hole cannot be angled up towards the crystal, down towards the case back, or off on a tangent. If it's off, it can cause alignment issues, extra wear on the movement, and snapped stems.

If you fill in the hole, then locating the new hole becomes much more difficult then just drilling out the hole as shown above.

Al, does the new tube have a slightly large OD? Kinda amazed you were able to recut threads like that.

Nope - it's just the same tube that was removed - well at least the same as it was before someone mangled it. I was just really following the existing threads, and removing the portion that was flattened out at the peak of the threads. As you can see, there's still plenty of thread left down at the root.

The case was pressure tested in both dry and wet testers, so it had the full Monty of testing. It passed in the dry tester just fine, and to 37.5 bar in the wet tester as well.

Yes, better repair method that welding or soldering a plug in. For something like that, without having the sort of fixturing that I've shown above, a jig borer would be the best option, with a vertical mill being my second choice.

Finding a shop that would take it on wouldn't be easy - they are all busy and shop time is expensive here - I know who I would ask, and it would be people at the shop I worked with a ton back in my engineering days when I was rebuilding a lot of machinery. I would definitely be calling in a favour for old times sake and buying my old friend Carl lunch!

Workholding is always a challenge because this is not raw material that you can just clamp up - it's already a highly finished piece with surfaces that are easily damaged. I would have to convince the customer to spend the money to try the repair, knowing that it might not work out. I wouldn't have an issue with a case repaired this way, but watch people can be funny sometimes - some may never trust it again with that sort of unofficial repair done. Thankfully none of that was needed.

This is the sort of advice we need more of.

Always nice to see the specilized tools.

There was a time when the watchmaker was expected to make such tools themselves. Tolerances and the statistical grading in this day and age make that a difficult proposition.

It IS nice to hear something other than that "the repair can not be done. Or can only be done by the manufacture."