Replacement Mainspring question
After several months watching 100s of videos, reading countless posts, and bidding on dozens of eBay non-runners, I have purchased a glorious vintage piece to attempt a repair on. Frustratingly, I disregarded all the advice in those posts and videos,(start with pocket watch, make sure it’s incabloc, get pictures of the movement before you buy), and purchased a 30mm, nonincabloc, piece from little known brand.
It has a broken mainspring. And a movement that I can’t find in the ranfft database. I’ve measured it to the best of my ability. And can’t find an identical one.
So here’s the question; how much smaller can the dimensions be and still expect it to function? Intuitively I don’t want to order anything that is larger on any dimension. But it seems like too small would allow excessive movement, leading to more wear and tear.
It’s a manual that will be worn once or twice a week at most. So power reserve is something that could be sacrificed.
Height 1.37
Thickness .09
Length 270
Barrel 9.4
Thanks for your reply.
Closest I’ve found is
1.35x.09x260x8.0
Closest I’ve found is
1.35x.09x260x8.0
The main dimension that you don't want to mess with is the height. If the height is a lot smaller, it won't wind evenly and could cause more wear. You should also never get a mainspring that is thicker, although a slightly thinner one could work. Since I'm assuming you don't have mainspring winders, you also want to make sure the diameter of the mainspring is smaller than your actual barrel so that you can push it in.
The one that you found seems to be a really good match, so I don't think it would cause any issues. I wouldn't worry about the .02mm difference in height and the slightly shorter length will affect the power reserve, but probably not by much. Good luck and have fun!
The link below may be useful, it's the list of main spring sizes from the Watchguy website
https://watchguy.co.uk/cgi-bin/mainsprings
The main dimension that you don't want to mess with is the height. If the height is a lot smaller, it won't wind evenly and could cause more wear. You should also never get a mainspring that is thicker, although a slightly thinner one could work. Since I'm assuming you don't have mainspring winders, you also want to make sure the diameter of the mainspring is smaller than your actual barrel so that you can push it in.
The one that you found seems to be a really good match, so I don't think it would cause any issues. I wouldn't worry about the .02mm difference in height and the slightly shorter length will affect the power reserve, but probably not by much. Good luck and have fun!
Appreciate your response. I’m going to give it a try.
The link below may be useful, it's the list of main spring sizes from the Watchguy website
https://watchguy.co.uk/cgi-bin/mainsprings
That’s an impressive list. If this first one goes well, that will definitely come in handy
Thank you.
That’s an impressive list. If this first one goes well, that will definitely come in handy
Thank you.
You're welcome 🙂