I am sending a 50s watch in for a service. The watchmaker does not change the spring unless requested. Do you change it even if the power reserve is ok?
The mainspring is the engine of the watch, and if it is not delivering adequate or consistent power to the train and escapement, all the tweaking in the world at the balance is not going to get you a good timing result. Now I'm sure there are watchmakers who don't have access to the parts (will likely be more common now) and those who think it's not needed, etc. but I change it on every watch I service. The only exception is usually some old obscure caliber that went out of production so long ago that the only springs available are blued steel springs - then there's not much point. But that is quite rare to have a watch where I can't find a new spring somewhere... Cheers, Al
Thanks Archer. Omega 505 most likely. Is it important to get an OEM spring, or are the aftermarket ones ok?
I use an OEM spring whenever possible. However for the Cal. 505 and family, you are out of luck as Omega does not supply mainsprings for these any longer. Base movement is a 470, so the mainspring number would be 72204701208 - this might help your watchmaker find one somewhere for sale. If he can't, then finding a generic of the right dimensions is all you can do. Bestfit lists the dimensions as 3 X 11 X 14 Dennison, which is 1.20 X .10 X 356 metric. Of course overall diameter and hook diameter have to be looked at as well. Cheers, Al