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Help with shorting a stem for a screw down crown


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Hi all,

I’m working on building a watch with a screw down crown and an NH35 movement. 
The screw down crown assembly does not have a spring mechanism, so Im concerned about getting the length correct so the crown will screw down correctly but also not put a load on the movement, and then of course unscrew and allow winding, setting. 
Any tricks for doing this? I’ve never done a screw down crown before. 
Thanks for any help with this,

Bill

0624113B-BF00-4F75-87C0-90071853A4EB.jpeg

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So no one here knows how to do this eh? Ok. 
thanks anyway. 
I did figure out that the crown assembly is spring loaded, and then I cut the stem too short. Got more ordered and I’ll get right next try. 

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Sorry for the silence. I guess everybody assumed that somebody else would answer.

I guess the "measure twice, cut once" advice would be a little late now.

The watch should be place in the winding position and the stem cut until the crown is able to wind without engaging the screw down threads. It's better to err on safe side and cut less initially and slowly adjust to the correct length.

Good luck on your second attempt.

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If it's spring loaded, it's just a "normal fitting" ?

What I'd do, is make sure the crown is screwed on fully, and the stem pushed in. Then using callipers, measure the distance shown - you don't need the number, just leave the callipers at that setting.
Then holding the stem in a pin vice, remove the crown and measure, from the end of the stem, the amount to remove using the callipers. Mark with a felt pen, then cut and file (to slightly longer at first), and try the fit.  
When happy with the fit, Loctite the crown.

image.png.dd963055130c982dd11641b193ea1b57.png 

SEE CORRECTION BELOW

 

Edited by mikepilk
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5 hours ago, HectorLooi said:

Maybe it's too early in the morning.... but if you measure and cut it according to the photo above, it'll end up too short. 

It should be measured from the end of the case tube to the bottom of the crown.

Morning HectorLooi, its 7am Now in Uk. Might that mean the bottom of the crown doesnt reach the case ? Depending on how much the tube is protruding.

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8 hours ago, HectorLooi said:

Maybe it's too early in the morning.... but if you measure and cut it according to the photo above, it'll end up too short. 

It should be measured from the end of the case tube to the bottom of the crown.

I think you are right. It was late (and wine was involved), and I wasn't thinking about the spring loaded crown.  

You want the bottom of the crown to sit flush with the end of the tube, then push in the spring loaded crown to screw tight.

image.png.4a9c150b39565c8107edd89edbf96dc6.png

 

Edited by mikepilk
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8 hours ago, mikepilk said:

I think you are right. It was late (and wine was involved), and I wasn't thinking about the spring loaded crown.  

You want the bottom of the crown to sit flush with the end of the tube, then push in the spring loaded crown to screw tight.

image.png.4a9c150b39565c8107edd89edbf96dc6.png

 

This is exactly what I did, and it came out too short. I probably just cut it so close to the mark that when I filed it down it made it shorter than needed. 
thanks for the help guys.  

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We learn from our mistakes, and I've made plenty, which is why I've improved so much 😄

At least parts are available and not expensive. You can buy stem extenders if you cut one too short and can't find a replacement.

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14 hours ago, mikepilk said:

We learn from our mistakes, and I've made plenty, which is why I've improved so much 😄

At least parts are available and not expensive. You can buy stem extenders if you cut one too short and can't find a replacement.

 

14 hours ago, mikepilk said:

We learn from our mistakes, and I've made plenty, which is why I've improved so much 😄

At least parts are available and not expensive. You can buy stem extenders if you cut one too short and can't find a replacement.

I still think you were  right the first time mike, so not so early or drank too much. Stem fully pushed home, the crown wound on fully. This is how it would be when the watch is running and on your wrist, the stem cant be any further in nor can the crown. Then the measurement taken from the case to the crown edge. Take this measurement from the stem end plus add a little back to allow for error in cutting and adjustment.

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15 hours ago, mikepilk said:

We learn from our mistakes, and I've made plenty, which is why I've improved so much 😄

At least parts are available and not expensive. You can buy stem extenders if you cut one too short and can't find a replacement.

Definitely worth having them in your parts stash as a backup  Mike 

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How is it possible to have a screw in crown without a spring loaded crown? I am confused.

I've not worked on a NH35 before. Without a spring loaded crown, how would the winding stem collapse in without breaking?

The only non spring loaded screw down crowns I've seen are Russian Amfibia and Komandirskie. And these are limp and flop around when the crowns are screwed out.

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1 hour ago, mikepilk said:

You are right @Neverenoughwatches. I misread the OP and thought the crown did have a spring. 

As these movements cannot be manually wound, you only need to be able to pull out the crown for setting. 

(I'll shut up now to stop more confusion 🙄 )

Haha. Its fine Mike, you just need that Yorkshire full English for brekkie.

1 hour ago, HectorLooi said:

The only non spring loaded screw down crowns I've seen are Russian Amfibia and Komandirskie. And these are limp and flop around when the crowns are screwed out.

They are fun to set the time, apparently to prevent damage to the stem adjusting time, date while on the wrist.

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The crown did indeed have a spring assembly, it was just stuck and I didn’t push hard enough to break it loose at first.  
I finely did get a stem cut correctly and it now works great. 
Here’s a photo of the finished watch. 
Thanks for the help everyone. 

3AFF6FD0-BD50-46DF-AF1A-DF7126CE3C16.jpeg

F424BEE4-7740-4CF9-B76A-B3882CC9CCCE.jpeg

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3 hours ago, BillM said:

The crown did indeed have a spring assembly, it was just stuck and I didn’t push hard enough to break it loose at first.

Yes, I  let you discover it for yourself. If you read my earlier post, it is impossible to screw in the crown unless there is some way for it to collapse down without crushing the stem.

Good job!

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Thanks H, my original post was pointing out that I was concerned about damaging the movement. It didn’t make any sense to me that the crown couldn’t collapse.  
lessons learned on our own are usually the ones that stick.  

Thanks again everyone.  

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