Screw broke off under its head

[Paquerette]

Greetings fellow watch enthusiasts,

I am new to the field of mechanical watch repair and have just encountered a problem that I could use some advice on. While disassembling my first watch, one of the screws broke off under its head, leaving the screw shaft stuck in the watch (please refer to the attached photo with the affected parts circled in green). I am now seeking guidance on how to proceed and find a solution to this issue.

I have tried using tweezers to extract the remaining screw shaft, but it seems to be tightly stuck and won't budge. I have also looked for online resources and forums for similar situations but couldn't find anything helpful. Therefore, I would like to reach out to this community for any suggestions or tips on what to do next.

I appreciate any insights or recommendations you may have regarding this problem. As a beginner in this field, I understand that mistakes happen, and I am willing to learn and improve my skills. I look forward to hearing from you and thank you in advance for your time and assistance.

 

Thank you !

 

Paqeurette

[JohnR725]

One of the problems when you're new to watch repair is surprises like screws that are left handed threaded. Sometimes on modern watches billing grave extra lines on the screw head so that you can see that it's a left-handed thread otherwise you just have to know that that's probably most the time a left-handed screw

there's a variety of ways to get the screw to go away. My favorite would be to make sure there's no other steel components on that bridge other than the broken screw. You can mix up a really strong solution of  alum  and with a little heat with by the way that has to be mixed in Thin glass or plastic but if you're heating it you can't use plastic so I would use glass. So if you warm it up it will dissolve the screw out and leave everything fine. You set the careful but there's no other steel components left or they will dissolve away also

Then you didn't say who made the movement? Because it might be possible just find another movement off of eBay And cannibalize it for the necessary parts.

[RichardHarris123]

Try heating the bridge to expand it. It might loosen the screw. 

[Nucejoe]

The crown wheel screw normall loosens in counterclock direction.

Bergeon tool 30209 is nice to have.

A 48hrs soak in Coca-Cola penetrates and cleans the screw threads, to a point that it unscrews easy. A needle or any tool of your choice is likely to work, thats  how easy a clean screw is to remove. 

Good luck.

[Paquerette]

Thank you for all your tips !

I finnaly found a replacement part on ebay (mouvement is FHF 26, but I didn't know yesterday, had to look for it).

 

But I will still try to keep the original bridge. When you talk about heat, sorry if the question is a bit stupid, but what type of temperature and tool ? I don't have a heat gun yet. Would an oven or hair dyer works?

 

[RichardHarris123]

I would try soaking in boiling hot water until the bridge reaches the same temperature.  There are special tools to remove broken screws but once hot, I would try a screwdriver on both ends and see If I could get enough friction.