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Fitting A New Watch Stem.

Geo

By Geo
in Your Walkthroughs and Techniques

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Geo Distinguished Member

Geo

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When fitting new stems to watches I use these tools :-

1-1.jpg

Digital calipers,

Fine grade diamond lap

Wire cutter

Pin vice

Now for fitting.

(1) Hold the stem in the pin vice and screw on the crown tightly by hand.

(2) With the movement fitted correctly in the case, insert the stem until it locks in place. Now measure the gap between the case and the underside of the stem. In this case it is 2.16mm.

2-1.jpg

(3) Subtract 0.2mm from this size and this will give the amount to remove from the stem. In this case it will be 1.96mm which will give 0.2mm clearance below the crown when fitted to the watch.

(4) Now remove the crown from the stem and hold the stem very tightly in the pin vice, then place the pin vice and stem between the jaws of the digital calipers then zero the calipers.

(5) Remove the calipers and without touching the zero button set them to minus 1.96mm. THEN RE-ZERO THE CALIPERS AT THIS LENGTH The wire cutters are now used cut off the excess thread leaving a small amount to be filed to the exact length.

(6) All that is required now is to dress the stem with the diamond lap a little at a time until the calipers read zero.

3-1.jpg

(7) Finally screw the crown on tightly and it should be ready to fit to the watch without further adjustment.

5-1.jpg

I find that this method cuts down on trial and error.

FOR SCREW DOWN CROWNS.

A) Screw down the crown tightly onto the case without the stem and measure the distance nbetween the bottom of the crown and the case.

B ) Screw the new stem tightly into the crown, then insert into the watch until it engages and locks into the movement.

C) Press the crown down firmly as far as it will go and hold it there.

D) Using the vernier callipers, measure the distance between the bottom of the crown and the case.

E) Subtract the size determined in (D) from the size measured in (A) then subtract a further 0.15mm from this size. This is the amount to shorten the stem by. This should allow the crown to screw full home without compressing the stem too tightly between the movement and the inside of the crown.

F) Cut the stem leaving it slightly longer than the size determined in (E), and dress down to size using the diamond lap and vernier callipers as described in the original post.

G) Screw the crown onto the shortened stem and check fit and function, before using a tiny spot of Loctite 221 to secure.

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Geo Distinguished Member

Geo

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OOPS, I forgot to say the calipers had to be re-zeroed again!

(5) Remove the calipers and without touching the zero button set them to minus 1.96mm. THEN RE-ZERO THE CALIPERS AT THIS LENGTH The wire cutters are now used cut off the excess thread leaving a small amount to be filed to the exact length.

Please edit this into the original post if possible Mark.

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SeikoWatch Super WRT Addict

SeikoWatch

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Thank you Geo..For my part I purchased the same type of stem and I measure the same length and I cut and I file the end of the threads of the stem. for me, this solve the problem..I'm lucky because it has never happened to have a watch with a piece of the stem. It is also rare that I buy a watch with a broken stem..Sorry for my bad english ;) your explanations are the best..

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Mark Distinguished Member

Mark

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OOPS, I forgot to say the calipers had to be re-zeroed again!

(5) Remove the calipers and without touching the zero button set them to minus 1.96mm. THEN RE-ZERO THE CALIPERS AT THIS LENGTH The wire cutters are now used cut off the excess thread leaving a small amount to be filed to the exact length.

Please edit this into the original post if possible Mark.

 

Your wish is my command :)

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Geo Distinguished Member

Geo

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FOR SCREW DOWN CROWNS.

(A) Screw down the crown tightly onto the case without the stem and measure the distance between the bottom of the crown and the case.

(B ) Screw the new stem tightly into the crown, then insert into the watch until it engages and locks into the movement.

(C ) Press the crown down firmly as far as it will go and hold it there.

(D) Using the vernier callipers, measure the distance between the bottom of the crown and the case.

(E) Subtract the size determined in (D) from the size measured in (A) then subtract a further 0.15mm from this size. This is the amount to shorten the stem by. This should allow the crown to screw full home without compressing the stem too tightly between the movement and the inside of the crown.

(F) Cut the stem leaving it slightly longer than the size determined in (E), and dress down to size using the diamond lap and vernier callipers as described in the original post.

(G) Screw the crown onto the shortened stem and check fit and function, before using a tiny spot of Loctite to secure.

This is now added to original post by Geo.

Edited by Geo
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bobm12 Distinguished Member

bobm12

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Hi Sendikumar,

 

The screw down crown has a spring between the stem and the crown (it is part of the crown ensemble) that creates a certain tension when properly screwed into the case tube. The spring tension translates into a shorter stem -- since the spring supplies the rest of the length -- and in the end it "takes back" that length to seal the watch...this is normally used in diving watches. Did I confuse you more? I'm not very good at explaining!

 

Cheers,

 

Bob

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