PLEASE HELP - crown tube tapping

[saswatch88]

Hello i have this very rare wwii elgin canteen diver. The crown is irreplaceable so keep that in mind. The stem broke and the other half is stuck in the tube and only a tiny bit is sticking out. I have tried everything from heating it soaking it in PB blaster and I cannot break it loose I’m pretty sure it is held in by glue or some sort of Loctite. Not to mention it’s been like that for 80 years and it’s rusted. I cannot get a tight enough grip on the tiny bit that is sticking out. I think the only way out of this one is to drill it out and then re-tap it with a number eight. However I do have micro drills And a crown tap set but this needs to be done with extreme Percision and I think it is a job for a watchmakers lathe which i do not have. I am wondering if there is anyone on this forum that can do such a task. I just need help I’ll pay whatever you want. I paid $1300 for this watch and if I can’t get this crown fixed it’s pretty much only good for parts.

 

 

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[watchweasol]

Hi  a bit sad, If it loctited in its going to difficult to remove in the whole. If the crown is all made of brass then using Alum (Aluminium Oxide) powder dissloved in hot water and soak the crown.  The Alum dissolves the steel but leaves the brass intact.  You are sure to get other opinions to consider and I wish you well

[saswatch88]

Hi  a bit sad, If it loctited in its going to difficult to remove in the whole. If the crown is all made of brass then using Alum (Aluminium Oxide) powder dissloved in hot water and soak the crown.  The Alum dissolves the steel but leaves the brass intact.  You are sure to get other opinions to consider and I wish you well

I considered alum but i think the crown is steel too. The case is parkerized stainless steel, so i will assume the crown is


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[jdm]

14 minutes ago, saswatch88 said:

I think the only way out of this one is to drill it out and then re-tap it with a number eight.

No. The way it's done is with a crown (hollow) mill on a lathe or boring machine. I know becuase I am being taught by a Master watchmaker that developed the below machine exactly to do that. The hollow end mill is hand made with a triangle file and then hardened. One only cuts just enough tube to grab the stem safely. I hope you can find someone that can do that for you.

[saswatch88]

No. The way it's done is with a crown (hollow) mill on a lathe or boring machine. I know becuase I am being taught by a Master watchmaker that developed the below machine exactly to do that. The hollow end mill is hand made with a triangle file and then hardened. One only cuts just enough tube to grab the stem safely. I hope you can find someone that can do that for you.

Do you think your guy can do it? I’ll pay whatever he wants. My only other option which is something I don’t want to do is basically grind the end of the stem down and re-tap the outside of the tube then use a stem adapter. Or Solder the stem directly to the tube. Both these options would be what I consider rigged and I am a stickler for details especially when it comes to these extremely rare watches


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[BrianB]

This may be a really stupid suggestion, but it can't hurt to throw it out there in case it sparks a better idea.

On a MUCH larger scale I've seen people use an arc welder, hook the ground to the part with the broken off "bolt", file the exposed surface of the broken threaded piece so it's flat, then hook the "positive" wire to a junk bolt that has a similarly prepped face, then touch the bolt to the broken off stud and the bolt gets welded to the broken off part. Then use a wrench to turn the broken off part out.

That said, if the stem broke in the first place whatever thread locker is holding it in the crown is probably is strong enough that what you tack weld to it in this manner would also just snap off.

What is the diameter of the original stem?

[jdm]

12 minutes ago, saswatch88 said:

Do you think your guy can do it? I’ll pay whatever he wants.

Answered in PM and for the record not for money.

My other observation is that on lathe, even a "model engineer" one with a collet chuck it is trivial to cut 1 or 2 mm off the tube.

Edited August 17, 2020 by jdm

[saswatch88]

This may be a really stupid suggestion, but it can't hurt to throw it out there in case it sparks a better idea.
On a MUCH larger scale I've seen people use an arc welder, hook the ground to the part with the broken off "bolt", file the exposed surface of the broken threaded piece so it's flat, then hook the "positive" wire to a junk bolt that has a similarly prepped face, then touch the bolt to the broken off stud and the bolt gets welded to the broken off part. Then use a wrench to turn the broken off part out.
That said, if the stem broke in the first place whatever thread locker is holding it in the crown is probably is strong enough that what you tack weld to it in this manner would also just snap off.
What is the diameter of the original stem?

Yes I have heard of that before but the problem is I don’t think there is nearly enough sticking out to weld. I don’t know the size I just know it is a tap 8 stem


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[rodabod]

I don’t think you want to attempt to cut into the existing stem as it will likely be harder than the crown pipe. 

If it’s any consolation, I recently repaired an original irreplaceable crown on a £7k JLC Mk11 and it worked out fine. 
 

There are many ways to skin a cat, but here is what I would do:

Firstly, I’d find out if the crown pipe is stainless, or at least significantly less likely to corrode than a carbon-steel stem. Usually this will be the case. Which opens up the opportunity to dissolve the stem in acid.

To dissolve with acid, you can suspend the crown such that only the end of the pipe is sitting in the acid. You can use an oiler to spread the rest of the pipe with silicone grease to acid-proof it. I’ve attached a photo of a crown from a 1980’s issued Precista military diving watch having this done just now. The corroded stem gathers at the bottom of the container.

 

[Marc]

53 minutes ago, watchweasol said:

using Alum (Aluminium Oxide) powder

Actually aluminium oxide is an abrasive grit, not soluble in water, and pretty inert.

Alum is potassium aluminium sulphate, water soluble and will dissolve steel but not brass, and not stainless steel.

I would be surprised if the crown were a plain carbon steel as this would make it rather prone to rusting as it's exposed to the outside world. If it's stainless or brass though then alum is your answer.

[watchweasol]

Hi Marc     Thanks for the correction  Wrong Alum .  I remember its used as a cut stick when shaving , good job I didnt use Aluminium Oxide  

[saswatch88]

Actually aluminium oxide is an abrasive grit, not soluble in water, and pretty inert.
Alum is potassium aluminium sulphate, water soluble and will dissolve steel but not brass, and not stainless steel.
I would be surprised if the crown were a plain carbon steel as this would make it rather prone to rusting as it's exposed to the outside world. If it's stainless or brass though then alum is your answer.

Ok It is 100% stainless steel. What is the correct name for the solution I need to look for. I will just go to my local Home Depot


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[saswatch88]

I don’t think you want to attempt to cut into the existing stem as it will likely be harder than the crown pipe. 
If it’s any consolation, I recently repaired an original irreplaceable crown on a £7k JLC Mk11 and it worked out fine. 
 
There are many ways to skin a cat, but here is what I would do:
Firstly, I’d find out if the crown pipe is stainless, or at least significantly less likely to corrode than a carbon-steel stem. Usually this will be the case. Which opens up the opportunity to dissolve the stem in acid.
To dissolve with acid, you can suspend the crown such that only the end of the pipe is sitting in the acid. You can use an oiler to spread the rest of the pipe with silicone grease to acid-proof it. I’ve attached a photo of a crown from a 1980’s issued Precista military diving watch having this done just now. The corroded stem gathers at the bottom of the container.
 

What solution did you use


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[Marc]

11 minutes ago, watchweasol said:

good job I didnt use Aluminium Oxide  

I've used razors before that felt like I was shaving with a 60 grit aluminium oxide paper!!!!   

[Marc]

10 minutes ago, saswatch88 said:

Ok It is 100% stainless steel. What is the correct name for the solution I need to look for. I will just go to my local Home Depot

As @watchweasol alludes to it's an astringent used in old fashioned wet shaving.

I use this as I have it around anyway (being convinced that the peak of shaving technology was reached in the late 1800's to early 1900's and everything else since has just been marketing hype to part a man and his money) and it works fine.

Interestingly enough as well as a shaving product, and for dissolving steel, it also makes an excellent un-perfumed deodorant, and is used as a food preservative, so you might be able to pick it up in the food aisle at your local supermarket in powder form.

[rodabod]

17 minutes ago, saswatch88 said:

What solution did you use


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Phosphoric acid. I wouldn’t bother with alum as you’ll be waiting until next year for it to finish off!

[Marc]

3 minutes ago, rodabod said:

I wouldn’t bother with alum as you’ll be waiting until next year for it to finish off!

Usually no more than about 3 days. Quicker if you keep it warm.

[rodabod]

I do use alum, but I find it can be very slow when dissolving stems which are trapped as there is so little material exposed. 

[saswatch88]

I do use alum, but I find it can be very slow when dissolving stems which are trapped as there is so little material exposed. 

It seems not one grocery store has alum in stock but i can get phosphoric acid. The tube is stainless steel but it was treated and it is not magnetic. The stem however is since its carboned steel. Will the acid ruin the tube too?


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[rodabod]

Acid will slowly attack the stainless steel. In theory, you should be able to dissolve the stem without affecting the crown pipe. 

[AlexeiJ1]

I mix up my alum, put it in a urine container/jar, then I drop it into a thermos full of boiling water for 3 days. Longer if needed.
I'd persevere with the alum. It will eventually get the job done.
Seiko use stainless steel stems in some models. I have been unable to dissolve a diving watch stem recently.

[jdm]

2 hours ago, AlexeiJ1 said:

I mix up my alum, put it in a urine container/jar, then I drop it into a thermos full of boiling water for 3 days.

Starting with the 1.3L model, ultrasonic cleaners come with heating. They are not expensive and ideal for maintaining a controlled temperature over time. Of course you would have to place the alum setup in bain-marie. 

[philipk5]

On 8/17/2020 at 11:33 PM, saswatch88 said:

It seems not one grocery store has alum in stock but i can get phosphoric acid. The tube is stainless steel but it was treated and it is not magnetic. The stem however is since its carboned steel. Will the acid ruin the tube too?


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Whereabouts are you? If in UK I can send a small amount of Alum. 

Cheers,

Phil

[saswatch88]

Whereabouts are you? If in UK I can send a small amount of Alum. 
Cheers,
Phil

Appreciate the help Iam in USA and I ordered some alum from ebay should be here by friday


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