Main spring replacement issue

vanjuxa

Registered User
Mar 31, 2013
221
5
18
United Kingdom
Country
First mainspring been broken
sealed part
Not sure if this is manufacturer issue ..
what is the best option for catching the hook

20210305_022309.jpg
 

Jerry Kieffer

NAWCC Fellow
NAWCC Member
May 31, 2005
2,926
550
113
wisconsin
Country
First mainspring been broken
sealed part
Not sure if this is manufacturer issue ..
what is the best option for catching the hook

View attachment 641473
Vanjuxa

I have bent the spring as is I suspect is common practice with success, but have never felt comfortable with the procedure.

My personal method is as follows

(1) To avoid the issues experienced with pin vises, I have machined a small watchmaker collet holder used in place of pin vises per first attached photo.

(2) The mainspring is inserted in the barrel along with the winding arbor. It is then mounted in the collet holder by the arbor and mounted in a vise per second photo.

(3) The spring is then pushed against the arbor while rotating the barrel where it will catch the arbor. Continue to rotate the spring barrel a few turns until the inner coil forms around the arbor and remains connected when the spring tension is released.

Jerry Kieffer

fullsizeoutput_534.jpeg fullsizeoutput_802.jpeg
 

DeweyC

NAWCC Member
Feb 5, 2007
2,404
949
113
Baltimore
www.historictimekeepers.com
Country
Jerry Kieffert thanks for advice
Now I know how to save this watch!

very uuuusefuuul

I have had several thousand mainsprings made from both Generale Ressorts and Schwab-Feller. In fact while In Switz. I visited Schwab-Feller.

Both manufacturers heat treat the inner coil to a specific arbor dimension. They will not take an order w/o the arbor size. Indeed, I had to send them an arbor and barrel for my M22 springs.

While probabilities rule life and manufacturing, both makers were quite insistent that the inner coil should not be manipulated (resized) because of the ultimate failure that will occur.

This does NOT mean the coil should not be manipulated to insert the proper size arbor. But it should not be reshaped to fit an incorrect sized arbor.
 

Jerry Kieffer

NAWCC Fellow
NAWCC Member
May 31, 2005
2,926
550
113
wisconsin
Country
For beginners that may read this, I would like to add to my post #5.

Regardless of spring supplier, sooner or later you will likely encounter a spring that will not connect to the winding arbor inner coil without assistance for whatever reason.
While the use of the winding arbor will be the safest method of fitting/forming such a spring, I use the method described on all watch mainspring installations and disassembly.
First, it is a very safe and easy way of rotating the spring to seat the arbor when installing a properly fitting spring. In addition and more importantly, it only takes a couple of seconds to apply a load on the spring and check the seated position on the arbor under a loupe. While this is not common, what I am looking for is where the tip of the spring is lifting the spring part way off of the arbor hook even under load. While this may correct itself under use, I never take the risk especially on a movement of value that is not equipped with a safety pinion.
An example of what can be encountered can be seen in the attached photos. (A handy uncleaned junk barrel and spring for illustration)

In the first photo, the spring is fully seated on the arbor per arrow no load.

In the second photo the same fully wound spring is not securely held in the original secure position and is a accident waiting to happen per arrow.
To apply the visible full wound position took all of 10 seconds to find a arbor issue that would not normally not be suspected. Since fingers are involved, it is a test done during disassembly. After cleaning, a modest load can be applied without touching the spring.

The procedure also allows the use of spring winding barrels to safely remove existing springs from spring barrels after a arbor test.

Jerry Kieffer

fullsizeoutput_80b.jpeg fullsizeoutput_809.jpeg
 
  • Like
Reactions: viclip

Forum statistics

Threads
165,007
Messages
1,435,874
Members
85,921
Latest member
Authenthic
Encyclopedia Pages
1,101
Total wiki contributions
2,873
Last edit
Weekly News 7/7/19 by Tom McIntyre