Mainspring replacement

[arron]

Good Saturday to you all,

 

I'm trying to replace the mainspring on an Elgin 10s Grade 22 pocketwatch; serial 948039.  I've never had to replace a MS when I didn't have the correct one to take measurements.  The existing MS broke during winding.  It's a modern MS which had been working fine before my COA; but the bridle tongue was actually on the wrong side (not on the sharp side of the catch, but rather on the sloped side of the catch, but it still worked.  I think the barrel-catch is to catch the MS hole, but the existing MS also has no hole at the end).  There is a cut out on the barrel lid for the bridle-catch to hook into but no cut out in the barrel.

I've spend a hours now trying to figure out how to order a new MS.  I tried the parts links in the PW database, but they took me to random watches and parts.  I've tried the different watch parts supply stores but i'm not finding a close match to the measurements I took and formula I found online for how to size a MS.  I'm also not finding a bridle with a hole and only one catch; most that I see have a T bridle, so there needs to be a hole in the barrel floor as well.  There is a drawing in the PW database showing this watch MS bridle with a hole and one catch.

The calculation I did was as follows:

Thickness: 15 (ID of barrel)/87=0.1724 mm

Length: 15 (ID of barrel)*30=450mm   (17")

Width: 3 (barrel depth)-.1 (clearance)-.45 (thickness of barrel lid)=2.45

The GR catalogue (I forget the exact name) lists an Elgin 10s PW and gives the demensions of: .17 thickness; 440 length; and 1.65 width.  Searching the cousins site using the GR# got me to this very MS.  the thickness and length are good I think, but the width seems pretty far off.  Also the bridle is the double brace and hole end; which maybe I could grind down the extra catch on the bridle.

I thought finding a replacement was going to be a lot easier than it has been but maybe I'm missing something.  Should I order the cousins MS or should I be looking for something else.  Thanks for reading.

  

[arron]

Hi Guys,

I'm hoping I can get help with one question on this mainspring.  I tried ordering an "original" mainspring off ebay but it was not the right one and doesn't fit.  It looks like the barrel catch was modified so that the new modern MS would catch and stay in place.  Since I can't find the original, I've decided to try and replace it with one similar to the modern one.  I found something on cousins, GR 6265 non auto, but it doesn't say what type of end it has to hook to the barrel catch.  Somewhere there I thought I read that if it doesn't specifically say what type of end, then it's the "standard" end.  I can't find anywhere on cousins where it lets you ask questions of support staff--it makes you search their FAQs.  I'm sure many of you have bought MSs from cousins.  Is the mainspring that I have, the one in the attached picture, a "standard" non auto end, or is it called something else?  Thank you. 

[Kalanag]

The standard end for non automatics is the „tongue“ as shown in your photo.

[arron]

Cool.  thanks for responding.  i'll go ahead and order it.