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Is there any "wiggle room" when it comes to replacing a mainspring?

Max50916
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Max50916 Watch Enthusiast

Max50916

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Forgive me if this is a dumb question. I'm currently working on an AS 1187 1194 movement which has a broken mainspring. I have a bunch of NOS mainsprings and would prefer to use one of possible. After looking into it, it seems the proper mainspring size for this movement is Denn. 6 x 11 -- 11.5

I've got ones close to that but not exactly that. So my question is, is it possible to use a mainspring with a slightly different width, strength, or length?

Is there more wiggle room in regards to any measurements in particular? (by that I mean, maybe there is no wiggle room in width but some wiggle room in strength etc) 

I've attached some photos with ones that seem to be relatively close, and am wondering your thoughts on using any of them? This is for a personal project so I'm looking to spend as little money as possible, otherwise I would buy a new mainsprings from Jules Borel.

Thank you for any help you can give!

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clockboy Distinguished Member

clockboy

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The correct spring for the AS 1187 is as follows:

H. 1.60  Thickness 0.105  L 220. Diameter 8,5

The correct spring for the AS 1194 is as follows:

H. 1.60  Thickness 0.105  L 280 Diameter 8,5

The difference between to two calibers is the length.
Personally I never move away from the correct spec unless it is absolutely necessary.  

If you move away from the correct spec the height must not be higher that the correct height , moving away from the correct length it will alter its standby time, strength, if too weak it might not give the correct amplitude and to strong can cause over banking.

 

 

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HSL Distinguished Member

HSL

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Posted (edited)

I'm thinking of those metric lenghts, 11 to 13 1/2 .. is that mm .. naah  Guess that is in inches so 220mm would be near 8 1/2 inches and 280 would be someting like 11 inches. The width (height) seems to be in mm.

So from those you have the 2750W is the closest. (If the bridle is ok).

Edited by HSL
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Max50916 Watch Enthusiast

Max50916

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1 hour ago, clockboy said:

The correct spring for the AS 1187 is as follows:

H. 1.60  Thickness 0.105  L 220. Diameter 8,5

The correct spring for the AS 1194 is as follows:

H. 1.60  Thickness 0.105  L 280 Diameter 8,5

The difference between to two calibers is the length.
Personally I never move away from the correct spec unless it is absolutely necessary.  

If you move away from the correct spec the height must not be higher that the correct height , moving away from the correct length it will alter its standby time, strength, if too weak it might not give the correct amplitude and to strong can cause over banking.

 

 

Thank you! Do you mind if I ask where you find these measurements since they didn't match up with what I'd found? Also, here's where it gets tricky, this movement is signed 1287 and 1294, what would you make of this? (See photo)

16210221605255343411115111464992.jpg

JohnR725 Distinguished Member

JohnR725

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Posted
4 hours ago, Max50916 said:

'm currently working on an AS 1187 1194 movement

In this particular case it doesn't make a huge difference but the numbers they give us initially and the picture and the later numbers it be nice if they all agreed. But just in case they don't I have links to both watches.

I even gave you the mainsprings for both watches you'll notice there's just a slight Height difference But that's not always the case of the numbers art exact for the caliber you have and it leads to confusion of somebody like me is reading from the beginning.

Hamas attaching a PDF to help with the confusion? If you try to substitute a mainspring that the height is higher than the barrel itself it will not fit. If it just barely fits will be too much friction and it's just a total waste of time. The length determines how long the watch runs if you go too far in length it won't fit in the barrel and the watch won't run at all and if it's too sure it just won't have running hours. But I'm commenting on extremes here. If it's too thick ill have too much power and you love too much amplitude that will be an issue. The same as to the end that you won't have enough power to run the watch as long as you're reasonably close you should be fine.

Then the reason why there's two numbers on the main plate is that basically both watches are identical except the diameter the movement. All the parts for one will interchange with the other except the main plate as a guess because that's what diameter the movement is.

 

so the mainspring for the 1287 from the links below is 1.50 x 9.0 x 0.10 x 290mm

The mainspring for the 1187 1.60 x 9.0 x 0.10 x 290mm Almost identical except the height

 

 

http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&0&2uswk&AS_1187

http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&0&2uswk&AS_1287

 

Mainspring - DennisonChart.pdf

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