Broken Screw Removal from Nickel Plated Movement

[nlapietr]

Good day.  I have a WWI Galco (Gallet) Trench watch with a FHF movement.  To hold the movement into the case there is a pin on one side and a screw (pocket watch type, i.e. round with half head removed) on the other side.   The screw was broken off when I bought the watch.  I believe the movement/main plate is Nickel Plated.  My question is can I use Alum powder in water to dissolve the screw or will that also screw up the nickel plating?  Thanks in advance.

[praezis]

Good question. I once removed a screw with alum solution from a nickel plated chronograph plate.
After, the nickel had considerably changed its appearance and looked different from the rest of the movement. I will not (and did not) do that again!

Frank

[nickelsilver]

 I have used 12% sulphuric acid, sold as Vissen by Bergeon, on nickel (German silver) parts to remove broken taps. I noticed that if the part wasn't super clean the acid could stain it, clean no problems.

 

If you have discoloration like Frank describes, often rubbing wet blanc de Meudon might restore the original color. This is a white powder also called blanc d'Espagne which is readily available in Europe but not sure elsewhere. French chalk works the same. It's also used in ceramics and as a base for gesso so art supply stores may have it.

[VWatchie]

If you can reach to screw from two sides you could also try with a screw extractor. I bought this tool some time ago and it worked really well. However, be aware that the tip of the extractors is very sensitive and easily deforms. Luckily the extractors are replaceable. Not cheap, like anything Bergeon, but as I said has worked well for me.

[Neverenoughwatches]

20 minutes ago, VWatchie said:

If you can reach to screw from two sides you could also try with a screw extractor. I bought this tool some time ago and it worked really well. However, be aware that the tip of the extractors is very sensitive and easily deforms. Luckily the extractors are replaceable. Not cheap, like anything Bergeon, but as I said has worked well for me.

I think i would also be trying this route first. Mechanical before chemical, mechanical approach more predictable?  For me personally i would say yes, you can stop at any point.

[nickelsilver]

23 hours ago, VWatchie said:

If you can reach to screw from two sides you could also try with a screw extractor. I bought this tool some time ago and it worked really well. However, be aware that the tip of the extractors is very sensitive and easily deforms. Luckily the extractors are replaceable. Not cheap, like anything Bergeon, but as I said has worked well for me.

I agree with this, but often the screw size is too small for the smallest setting of the tool. You can then make on your lathe new bits, or use a jeweling tool. Make a pusher and stump in unhardened steel that fit. Clamp the (hard steel screw) between the two, and unwind the stuck bit turning the plate around. Has worked for me more times than the (well conceived) Bergeon tool. The unhardened steel grips the hard screw quite well.

[VWatchie]

7 minutes ago, nickelsilver said:

You can then make on your lathe new bits

So another reason to get a lathe! I guess it will pay off in the long run. And if (when?) I get one I will probably wonder how I ever could be without it 

[TimeWerks]

I have a similar problem with a twist.  I have a dial screw that is broken so the screw is on the edge of the movement and the dial is still attached.  

 

I could try a bit if crazy glue on the end of screwdriver blade, but not sure it wouldnt sheer off due to the torque, and also worried I might make things worse with the glue.

I ordered a set of screw extractors (simple hand tools) but the bit sizes were too large.  Could try to make a extractor type bit out of high speed steel, somehow secure the movement flat on a tool platform on a watchmakers lathe, and try running the lathe in reverse pushing the fabricated extractor against the remaining screw thread.

If that doesn't work, I was going to follow an old recommendation and use a really small drill bit in the normal direction, along with a subsequent broach.

Any other suggestions welcome.  

 

[praezis]

On 9/27/2022 at 10:39 PM, VWatchie said:

So another reason to get a lathe! I guess it will pay off in the long run. And if (when?) I get one I will probably wonder how I ever could be without it 

Exactly how it will be! You can save at least 100 "special" tools if you have a lathe. I use mine daily for 1000 small  tasks that have nothing to do with turning a balance staff or so.

Frank

[Neverenoughwatches]

47 minutes ago, praezis said:

I use mine daily for 1000 small  tasks that have nothing to do with turning a balance staff

tool making money saving guru Frank. I hope you are up for giving some of these ideas away.