Broken Stem Inside Crown...

[KyleP88]

Hi. A friend has snapped off the stem flush with the crown on a Miyota 2035 movement. Is there anyway I can remove the broken stem from inside the crown as there is no protruding stem to grab hold of. Thanks for reading. Kyle

[chrisdt]

A new Miyota 2035 movement  complete with stem is only around £3.50.

Cut to the right length and fit a new crown. A lot easier than drilling the crown.

You will need a new stem anyway because the old one will be too short.

Chris

[Ishima]

If you wish to re use the crown (though an appropriate replacement shouldn't be too hard to source just looking at the picture) you can corrode out the steel of the stem over the course of ~a week using a solution of water and aluminium potassium sulphate (easily found online, it's used to whiten bread), this rarely if ever effects the crown itself as it is made up of different metals or stainless steel, not regular steel. 

Edited September 16, 2016 by Ishima

[Brian3]

Vinegar works too, will take a good few days to fully dissolve the stem but it's good, I use it whenever required.

[KyleP88]

thank you for the replies everyone. most helpful. Brian whats the ratio of vinegar to water or is it just 100% vinegar with the crown fully submerged? thank you. Kyle

[parmenion31]

You can read this post too , its older but you may find something usufull

 

 

[Stian]

Hi guys,

 

The stem on this watch was bent close to the crown, and snapped off, leaving a tiny piece inside the crown. The piece is too small to get hold of with a tool.

 

 

Is it an option to use Alum to dissolve the system piece, or would that damage the crown in the process? Do you have other suggestions for getting the broken stem out?

 

Thanks,

Stian

 

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[jdm]

Just replace the crown. Other attempts would probably just waste time and produce frustration.

 

[RyMoeller]

I have used alum to remove a broken stem from a crown before.

[clockboy]

A new crown would be my option. If not then drill it out but be warned it could damage the thread of the crown if not careful.

[Stian]

Thanks, guys. This is an original crown for a vintage watch, so replacing it is really the last option.

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[Stian]

I have used alum to remove a broken stem from a crown before.

Thanks, did that in any way damage the crown?

Stian

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[RyMoeller]

7 hours ago, Stian said:

Thanks, did that in any way damage the crown?

Stian

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No, but I hesitate to say you'll have the same result.

The alum water solution will react with carbon steel (the stem) but the thing to remember is if there is any carbon steel in the crown then it's at risk as well.  Most crowns seem to be either plated brass or stainless steel and alum doesn't seem to be very reactive with those metals.

[vinn3]

just apply a little penitrating,  soak if posible - dry and  heat with a jewelers torch.  stem stub should screw out.

[jdm]

just apply a little penitrating,  soak if posible - dry and  heat with a jewelers torch.  stem stub should screw out.

Really! And how one would grab a stem snapped flush as in picture above?

[jdm]

Thanks, guys. This is an original crown for a vintage watch, so replacing it is really the last option.

Vintage of a value such to require full original parts? You will be surprised at the variety of a good crown assortment.

[Stian]

A new crown would be my option. If not then drill it out but be warned it could damage the thread of the crown if not careful.

Thanks, and what is the best way to drill the old screw out then?

Stian

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[rogart63]

54 minutes ago, Stian said:

Thanks, and what is the best way to drill the old screw out then?

Stian

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In a lathe? with a small drill then larger and larger until you can remove the threads? But not sure it will work? 

For what  watch  is it? 

[Stian]

In a lathe? with a small drill then larger and larger until you can remove the threads? But not sure it will work? 

For what  watch  is it? 

It's for a Zenith 133.8

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[rogart63]

There is crowns for Zenith on Cousinsuk if it doesn't work. But i guess they are only for the newer Zenith? 

Edited February 2, 2017 by rogart63

[Stian]

There is crowns for Zenith on Cousinsuk if it doesn't work. But i guess they are only for the newer Zenith? 

Yeah, and fit vintage watches it's really important for the value to keep it original as far as possible... But thanks anyway

Stian

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[vinn3]

"how would I grab the stem - stub"  that is the chalage.  first get penetrating oil down alongthe threads.  (I prefure it to allum).   NOW to turn out  the stub.  one way is to use a left hand turning drill.  first try  moving it with a very small punch.  BUT most would just buy a new one (save the original).  vinn

[StuartBaker104]

Stian, it's likely that the stem is done up tightly or possibly even loctited in place. If the latter then this will be a challenge to deal with. You can try alum, but any plain steel parts will be attacked too.

Loctite threadlockers for this kind of application should be low strength, but you have nothing to hold on to, so that won't help much. The strength is dramatically reduced by heating to about 250C, but if you have a rubber seal in there, you don't really want to exceed that for long. Sometimes the washer can be prised off so you can remove the seal and then heat without fear. If it's a regular o-ring then that means you can also fit a new seal afterwards.

The stem is hardened and therefore will be difficult to drill, but not impossible.  Because the stem is hard, if it has broken with a ragged edge, that will make drilling it centrally more tricky. The upside is that this means you may be able to use a screwdriver to turn it - hold it in a pin vice whilst still hot.

If the surface is completely flat, you are going to have to drill it, and as others have said a lathe gives you the best chance of centring things. I would heat it for an hour or so first to help break down any loctite present.  What you are trying to do is to drill out to the thread root diameter (of the stem, not the crown!) and then you should be able to chase the remainder out with a tap or fine needle. If you end up drilling off centre then just make sure your drill is small enough to stay inside the thread root and not damage the thread in the crown.

 

 

[jdm]

If using alum one can suspend the crown so that only the interested part gets submerged. And I wouldn't even think of drilling without a lathe and the appropriate bits. Either way, good luck.

[Andyclient]

I had a stem broken flush in a signed vintage Camy crown , so replacement wasn't really an option .

I got some alum powder cheap from Ebay and gave it a go , I have to say if i hadn't seen it with my own eyes i would of doubted it at best ,or never believed it at worst. In approx 24hrs the old stem had completely dissolved away.

Maybe i was just lucky but it worked for me , I did make a strong solution and read that it worked best warm so warmed it up also, if it's working you will see bubbles coming from the stem.

Good luck