Stem broken in crown, advice please

[d3xmeister]

Hi fellow watchmakers ! I have a watch with a broken stem in the crown. The crown is a special shape, and signed (Orient Star) and it cannot be sourced from the manufacturer. I can find stem (any modern Orient stem works) but I would like to recover the crown. How do I remove the broken stem part from the crown ? Obviously it is also glued in there.

[Marc]

Your best best is to dissolve it out using a solution of alum.

You may have to give it a day or two at room temperature, or you can always warm it up a little if you're in a hurry.

[rossjackson01]

15 minutes ago, Marc said:

Your best best is to dissolve it out using a solution of alum.

You may have to give it a day or two at room temperature, or you can always warm it up a little if you're in a hurry.

I failed miserable with alum. Tried that for a crown. Everyday couple of days for 1 month. No discernible reduction in the stem. Have ended up having to buy a replacement crown. Boo hoo.

[rehajm]

I’d be curious to know if this could be drilled out? I have a gold back plate with broken screws and I’m frightened of alum…

[Marc]

2 hours ago, rossjackson01 said:

I failed miserable with alum. Tried that for a crown. Everyday couple of days for 1 month. No discernible reduction in the stem. Have ended up having to buy a replacement crown. Boo hoo.

It's unusual that you had no luck with this method as it's a well established technique for dealing with the removal of otherwise inaccessible steel casualties from non-ferrous parent material. There are a couple of possible explanations for this though, the first of which is that the stem was made of stainless steel (alum doesn't dissolve stainless steel), which would be unusual but not impossible; the second is that it was the wrong kind of alum.

Technically "alum" refers to a range of compounds (see here). It may well be that some alums are better than others for dissolving steel. I believe that the one to use is potassium alum KAl(SO4)2·12 H2O. This has always worked well for me.

18 minutes ago, rehajm said:

I’d be curious to know if this could be drilled out? I have a gold back plate with broken screws and I’m frightened of alum…

I think I'd be more worried about the potential for damage from a slipping or breaking drill bit, or the drill bit actually impinging on the threads in the parent material. I'm pretty certain that the alum won't stain or otherwise damage the gold, however, a simple experiment with an otherwise redundant gold plated item would answer that question.

[rehajm]

29 minutes ago, Marc said:

I think I'd be more worried about the potential for damage from a slipping or breaking drill bit, or the drill bit actually impinging on the threads in the parent material. I'm pretty certain that the alum won't stain or otherwise damage the gold, however, a simple experiment with an otherwise redundant gold plated item would answer that question.

Thanks. I know I can’t use an alum in my case since the support structure of the case back would likely be dissolved as well. I see videos of train wheels being pivoted with tiny drills in lathes and such so I’m desperate/hopeful there’s an alternative…

[ColinC]

3 hours ago, d3xmeister said:

Obviously it is also glued in there.

You suspect the stem is glued in there with superglue - what about soaking it in some acetone and then seeing if it will move?

[rossjackson01]

1 hour ago, Marc said:

It's unusual that you had no luck with this method as it's a well established technique for dealing with the removal of otherwise inaccessible steel casualties from non-ferrous parent material. There are a couple of possible explanations for this though, the first of which is that the stem was made of stainless steel (alum doesn't dissolve stainless steel), which would be unusual but not impossible; the second is that it was the wrong kind of alum.

Marc.

Wrong metal? I think you are correct. When I look a the broken stem it really does shine. Cannot mark it with tweezers or screwdriver.  What I do have, as a Christmas present to open in a few days time (woohoo) is a screw removal tool. Not sure if it would work on a sealed end product like the crown. But, who knows?

 

[Marc]

1 hour ago, rossjackson01 said:

Not sure if it would work on a sealed end product like the crown. But, who knows?

@rossjackson01 you can but try

[rossjackson01]

Marc

Like your site https://watchmender.wordpress.com/, especially the eta 2789-1. This movement was my first attempt. 3 pivots broken, 'pings' everywhere. Did not photograph anything.  1 month later began Marks course and found out where I went wrong. Ha!

Edited December 21, 2023 by rossjackson01

[nevenbekriev]

4 hours ago, rehajm said:

I’d be curious to know if this could be drilled out? I have a gold back plate with broken screws and I’m frightened of alum…

No need to be frightened of alum, but it will not dissolve the screws - they for sure are stainless steel. I guess that they are big enough, e.g. 0.8 mm in diam, so drilling them is normal choice, but do it carefully. If 0.8, then 0.5 drill bit (carbide) should be used. I do it by hand, the drill bit in pin vise. After the drilling, a tool like reamer shoud be pressed in the hole, then the tool gently forced in both directions - screwing and unscrewing, many times, untill the screw begins to move a little, when this happens - success is close.

[Neverenoughwatches]

1 hour ago, rossjackson01 said:

Marc.

Wrong metal? I think you are correct. When I look a the broken stem it really does shine. Cannot mark it with tweezers or screwdriver.  What I do have, as a Christmas present to open in a few days time (woohoo) is a screw removal tool. Not sure if it would work on a sealed end product like the crown. But, who knows?

 

Like you say Ross these extractors act on both ends of the screw at the same time turning out the screw rather than drilling it out.. Somehow it needs to get a bite on the broken end leaving the crown head untouched. Its possible to drill stainless steel, not sure if you could buy anything that small that would have any chance of not breaking off inside. A 0.9mm double fluted hss or carbide drill bit will likely have a central web of well under 0.2mm. The pros would use something like a carbide boring bar that has more body to it. Interesting idea to find a good solution to the problem, ive been waiting 2 weeks now for some sodium bisulphate for different uses I'm in an experimenting mood at the moment as you can tell. 

7 minutes ago, nevenbekriev said:

No need to be frightened of alum, but it will not dissolve the screws - they for sure are stainless steel. I guess that they are big enough, e.g. 0.8 mm in diam, so drilling them is normal choice, but do it carefully. If 0.8, then 0.5 drill bit (carbide) should be used. I do it by hand, the drill bit in pin vise. After the drilling, a tool like reamer shoud be pressed in the hole, then the tool gently forced in both directions - screwing and unscrewing, many times, untill the screw begins to move a little, when this happens - success is close.

I still want to know where you get your carbide bits from Nev, the ones i have are like brandysnap.

[rossjackson01]

Never

"Like you say Ross these extractors act on both ends of the screw at the same time turning out the screw rather than drilling it out.. Somehow it needs to get a bite on the broken end leaving the crown head untouched."

I do have an idea, but need to wait until I can open the present. I intend to put two crowns back to back, solid against solid. Place a screw lightly into one and then begin the screw system of turning the loose screw into the crown and hopefully the other out. Will let you know before the new year.

[nevenbekriev]

10 minutes ago, Neverenoughwatches said:

I still want to know where you get your carbide bits from Nev, the ones i have are like brandysnap.

Before the Brexit, I used ebay.co.uk and a company named GABIELI  UK to BG that delivers from UK to Bulgaria goods bought by bulgarians from Ebay. Now i use Aliexpress, delivery is from China and takes about 3-4 weeks normally. The drill bits are the same as what You have, I order normally 1-2 times per year and have ordered more than 10 times till now.

[RichardHarris123]

Heat would break the bond of the glue.  After that, probably no choice but to drill. 

[Neverenoughwatches]

3 minutes ago, nevenbekriev said:

Before the Brexit, I used ebay.co.uk and a company named GABIELI  UK to BG that delivers from UK to Bulgaria goods bought by bulgarians from Ebay. Now i use Aliexpress, delivery is from China and takes about 3-4 weeks normally. The drill bits are the same as what You have, I order normally 1-2 times per year and have ordered more than 10 times till now.

I must be doing something wrong with them then, i broke five in a row trying to hand drill a hole in some carbon steel.

[nevenbekriev]

9 minutes ago, rossjackson01 said:

Never

"Like you say Ross these extractors act on both ends of the screw at the same time turning out the screw rather than drilling it out.. Somehow it needs to get a bite on the broken end leaving the crown head untouched."

I do have an idea, but need to wait until I can open the present. I intend to put two crowns back to back, solid against solid. Place a screw lightly into one and then begin the screw system of turning the loose screw into the crown and hopefully the other out. Will let you know before the new year.

Ross, drillinfg is the way to rid out the broken piece. This is done in the lathe, the bit is drilled thru, like tube. Then tool with grains, like reamer, is pressed in the piece. The crown has to be heated to melt the thread fixer and then the piece will unscrew.

I will advice not to risk breaking the new tool. It is usefull, but not in this case.

3 minutes ago, Neverenoughwatches said:

I must be doing something wrong with them then, i broke five in a row trying to hand drill a hole in some carbon steel.

I don't know why. You have to be gentle and steady.

If You nave seen the video I made with drilling clock spring, the bit may chip in the end of the hole, when the tip of the bit is about to go thru. In the whole process of drilling, this is the dangerous moment. And, when the hole gets deep (3-4-5 X diam), it may happen that the bit will begin to stuck and turn in the hole with great friction, then it will break if continue drilling. The solution then is to sharpen the tip not symetrically - the one cutting edge to be longer than the other. Thus the diam of the hole gets bigger than the bit diam.

[CYCLOPS]

white vinegar will dissolve steel, I have used it on broken screws in main-plates before, it might be your only choice, I think the stainless crown should be safe in vinegar, if dis-colored the crown can be polished...

[d3xmeister]

How would white vinegar dissolve the leftover stem inside but not the rest ?

[Neverenoughwatches]

5 minutes ago, d3xmeister said:

How would white vinegar dissolve the leftover stem inside but not the rest ?

I've used vinegar extensively on watch parts in the past, the acetic acid does eat away at rust though I've  never known it to dissolve parts . In time i assume it would , it turns good steel grey and etches the surface. I dont use it anymore, i dont like the flash rusting that can occur on steel. But on a brass crown it wont effect the brass.

[CYCLOPS]

most stems are regular steel and rust which the vinegar attacks, most crowns are stainless steel and are somewhat resistant to chemicals, I don't like to use vinegar either but in your case if the crown does not come apart in pieces like older Rolex crowns do you have no choice but drill, dissolve or replace.....