American PW Elgin mainspring part number

admitch

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Jun 5, 2010
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The Elgin movement serial # is 26947394, a Grade 303 Class 144 12s 7j Code 03n3p.

I need to order a mainspring replacement for a 1923 Elgin watch. I know I can send the serial # to a vendor for their evaluation, but how do you know you are getting the one which should be used? Being new to watch repair, I am trying to understand everything. I would prefer to look in a parts catalog and select a part number! However, I understand that a lot of the info has been lost over the years. The Elgin information on Elginwatches.org was very useful, but limited in a couple of areas. The website had a 1915 materials catalog, but the movement is 1923. The grade and class was in use prior to 1915, so it may be accurate.

The 1915 MC gives several choices for 12s. Some choices have the same part number but different thickness. As follows:
PN 1712 for steel barrels - .184mm thickness for 19j, 23j
PN 1712/2449 for steel barrels - .190mm thickness for 7j, 15j, 17j
PN 1720 for thick going barrels - .184mm thickness for ? j
PN 1720 for thick going barrels - .190mm thickness for 7j, 15j, 17j
PN 2339 for thin going barrels - .184mm thickness for ? j
PN 2339 for thin going barrels - .190mm thickness for 17j
PN 2339 for thin going barrels - .196mm thickness for 7j, 15j
PN 6329 for thin going barrels "Elgin Dura Power" same as 2339

There was no selection based on Grade or Class. I assume the steel barrels were used in early watches. I know the number of jewels but not the barrel type. I looked up the barrels in the MC and found 2 for Class 144, thick and thin.

Can you order different thickness for the same part #?

O.K. people, what PN should be selected and WHY?
 

richiec

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Admitch, According to the information that I have, you should be using a 2339 mainspring and a 2177 barrel for model 3 after movement 10388201, hope this helps you.
 

admitch

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Thanks Richiec, this is very helpful. I have several Elgin PW's of this time period. I was wondering if you knew where this info came from? Also, there are three thicknesses listed for 2339. Can you order different thicknesses for this part?

I guess I am a fanatic for authenticity in some watches. I only have access to the Elgin 1915 MC on the Elginwatches.org website. This websites states there are other MC's (1927, 1950, etc), but I have not found any.
 

mooredan

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Jan 23, 2022
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Is there a measurement, or visual clue, that to determine if a barrel was of the "thick" or "thin" type? Elgin PN 2100 and 2177. I assume that the thick and thin designation refers to the wall of the barrel. I have a 12s barrel and the average wall thickness is 0.48mm (18.9 mils)
 

Rick Hufnagel

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Hey Mooredan, welcome to the forum!

Thick and thin would refer to the barrel height and determine the mainspring. Your numbers are not exactly ringing a bell, can you provide a photo of the movement or the serial number?
 

mooredan

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Jan 23, 2022
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Thanks Rick, Oh, I misunderstood what is meant by thick and thin. This refers to the height of the barrel, and the thickness of the wall, correct? Here's a photo of two barrels. I measured the thickness being 2.78mm (left) and 2.74mm (right). If these are the same part number, but I still do not know which part number. Is this the 2100 "thick" barrel taking the 1720 spring, or is it the 2177 "thin" barrel taking the 2339 spring.

These barrels came from:
Elgin S/N 27843356, grade 303, class 114, model 3 (left)
Elgin S/N 13148150, grade 301, class 113, model 2 (right)

The barrel on the left has a problem, the lid will not snap shut, even without a spring installed. I've tried using the Bergeon 7922 tool, the flats of a couple of pairs of tweezers and my fingers. No matter what, one side will always pop up.

BUT WAIT! After uploading the photo, these are NOT the same. Note the inner collar, on the left it is like a cylinder, and on the right it is more like a funnel. ...is this what is meant by thick and thin?

And the lids are slightly different too. The arbors look the same.

IMG_3114.jpg

IMG_3115.jpg
 

Rick Hufnagel

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Thick and thin refers to the height of the mainspring.

The thicker barrels take the 1720 mainspring which is 2.23 mm wide

The thinner barrels take the 2339 which is 2.05mm wide.

It shows the same arbor for class 113 and 114 so no difference. Part number 1715.

The different barrels have different inside heights
Screenshot_20220221-230143~2.png Screenshot_20220221-225958~2.png Screenshot_20220221-225042~2.png

If you are trying to switch those barrel caps .. it's not going to work. You'll need to find another similar barrel.
 

mooredan

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Jan 23, 2022
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It's the inside height is different, not the outside height.

Just to summarize:
  • The thick barrel (PN 2100) has a greater inside height to accommodate the wider main spring (PN 1720) 0.088" (2.23 mm)
  • The thin barrel (PN 2177) has a smaller inside height which takes the narrower main spring (PN 2339) 0.081" (2.05 mm)
  • The barrel arbor (PN 1715) is the same for both thin and thick barrels
You are correct, the barrel lids are not interchange-able, but maybe the entire barrel is. I was thinking about just swapping out the entire barrel, since the arbor is the same and the measured outside thickness of the barrels are the off by just 40um (the replacement is shorter).
 

mooredan

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Jan 23, 2022
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After some more investigation, I'm inclined to conclude that these two barrels are variants of the thin barrel P/N 2177. One reason for this are that the springs removed from both measured to be about 2.05 mm (+/- a few microns). Another reason is that I calculated the height of the cavity based upon measurements of the lid thickness, bottom of the barrel thickness, and height of the barrel. They differ by 6um, which is third of what I would expect if one of these barrels was the thick variety and the other of the thin variety.
Barrels.png

Therefore my answers to the questions posed are:

- Yes
- P/N 2177

Opinions? Thanks, Dan
 

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