How to take out a broken screw inside the barrel arbor?

[EatPeach]

So half of the rachet wheel screw is broken inside the barrel arbor, I can take the upper half out apparently. The problem is how should I take the rest of it out? I'm thinking about use the liquid which used to soak the broken stem inside the crown. But I'm not sure this is a safe solution. Will the arbor survive after the soak? And will the screw dissolve (I guess the material of the stem is different from the screw)

Thank you guys!

[watchweasol]

The fact you have a steel screw inside a steel arbour negates the use of acids/alum as it will attack both parts. try using a needle point to unscrew the remains and be aware it may be a left hand thread,     Other wise a screw extractor may be the only way.  Is the screw broken by the head or is it lower down in the arbour. A photo of the arbour and screw stub may be  useful so other members may see and appraise the problem.         cheers

[Cmmb8519]

Put it in the ultrasound cleaning machine for 5 min. Might come out if not too tight

Sent from my SM-G975F using Tapatalk

[steve1811uk]

I had the same thing happen to me when winding up a movement via the barrel screw. Lesson learned that in future only do that for one or two turns when the barrel is completely wound down. I was lucky though as the screw sheared right near the top and I could tease the threaded part out with a needle.

Sent from my Moto G (5) Plus using Tapatalk

[EatPeach]

Put it in the ultrasound cleaning machine for 5 min. Might come out if not too tight

Sent from my SM-G975F using Tapatalk

yeah I tired. No luck

[toptime810]

ALUM is what you need to extract the screw.

[JGrainger]

You could try a 3 or 4 sided centre, gently tapped onto / into the middle of the thread to create an impression, then rotated to unscrew it.

If all else fails and the part is basically scrap (and you enjoy trying overly tedious methods) then it might be possible to carefully examine the remaining threads to see whether it's a left or right-hand thread, then carefully try drilling the remaining thread in the opposite direction (by a hand method with an optical aid). Checking the hardness of the other half of the part might allow you to discover which type of drill might work - there's also a high chance of breaking a drill or damaging the threads you want to save. The tiny hole then might be a candidate for trying to stick a tapered faceted steel pin into to use as a thread extractor.

The hole could be started with a 3 or 4 sided pointed tool to create a centre in the stuck piece.. possibly with a tiny brass bush on the outside so that it can centre on the existing threads without damaging them. It might also get enough grip to remove the part if rotating in the correct direction to undo it.

In theory it could also be possibly to use spark erosion to drill through the remaining thread so that you can stick something in it to unscrew it.

[EatPeach]

1 hour ago, toptime810 said:

ALUM is what you need to extract the screw.

You mean that chemical？ Will it harm the arbor as well?

[EatPeach]

24 minutes ago, JGrainger said:

You could try a 3 or 4 sided centre, gently tapped onto / into the middle of the thread to create an impression, then rotated to unscrew it.

If all else fails and the part is basically scrap (and you enjoy trying overly tedious methods) then it might be possible to carefully examine the remaining threads to see whether it's a left or right-hand thread, then carefully try drilling the remaining thread in the opposite direction (by a hand method with an optical aid). Checking the hardness of the other half of the part might allow you to discover which type of drill might work - there's also a high chance of breaking a drill or damaging the threads you want to save. The tiny hole then might be a candidate for trying to stick a tapered faceted steel pin into to use as a thread extractor.

The hole could be started with a 3 or 4 sided pointed tool to create a centre in the stuck piece.. possibly with a tiny brass bush on the outside so that it can centre on the existing threads without damaging them. It might also get enough grip to remove the part if rotating in the correct direction to undo it.

In theory it could also be possibly to use spark erosion to drill through the remaining thread so that you can stick something in it to unscrew it.

I will try. But the hole is too small. I need a set of tools to continue doing anything. I dont even get something that small to get into that hole.