Is this a usual occurrence?

[Lotus]

I'm currently about to order mainsprings for 2 movements I've been working on, and the barrels inside diameter for each movement is 9.5 and 10.5 respectively. However, when I go on Emmywatch, which I use for movement research and, at least I believe, has accurate information, the mainsprings for the movements both have a barrel diameter of 9.0! Is it usual for mainsprings to have smaller barrel diameter specifications, and if so, why do these 2 mainsprings have the same barrel diameter listed even though they are supposedly for completely different diameters?

Barrel diameter 9.5: https://www.emmywatch.com/db/movement/vulcain--65ms/

Barrel diameter 10.5: https://www.emmywatch.com/db/movement/lemania--ds27/

[AndyGSi]

I've found Emmy to be very hit and miss with correct information and wouldn't pay much
attention to what they show as barrel size as long as the rest of the details are correct.

[praezis]

The diameter of mainsprings is that of the container ring! It must be smaller than the barrel, if you want to mount the spring without special winder.

Frank

Edited June 25, 2024 by praezis

[Knebo]

8 hours ago, AndyGSi said:

I've found Emmy to be very hit and miss with correct information and wouldn't pay much
attention to what they show as barrel size as long as the rest of the details are correct.

Agreed, It's not the most reliable source.

[VWatchie]

10 hours ago, AndyGSi said:

I've found Emmy to be very hit and miss with correct information

1 hour ago, Knebo said:

Agreed, It's not the most reliable source.

In my experience, CousinsUK.com do usually, but not always, a good job of recommending the correct spring. Even so, in some cases, you need to remove the spring from the retainer ring (when it's larger than the diameter of the barrel) and wind it into a mainspring winder or wind it in by hand.

Oh, I just saw that you're in the US, but you can still check what CousinsUK recommends and buy elsewhere. I just had a look and unfortunately CousinsUK have no recommendations for these movements.

 

[Knebo]

This list here from WatchGuyUK is also very helpful: https://watchguy.co.uk/cgi-bin/mainsprings

With the info you find there (by size and/or GR reference), you can go to CousinsUK and see if they also list your calibre for that spring. If both agree, you can be quite sure.