Old v. NOS Mainspring?

[grsnovi]

I thought that if I purchased a replacement mainspring, it would arrive wound such that I could pop it into the barrel without having to use a winder. The spring that I received isn't packaged like that and somebody elsewhere suggested that as old as it is, it may have taken on a "set". So, were I to use the NOS spring, will it get the tightly wound curve around the arbor from being wound in the winder or will I have to do some prep to it prior to feeding it into the winder? Would I be better off putting the old spring back in? While it looks ok, the coil doesn't seem to be a uniform spiral.

[oldhippy]

Did you buy it new? If so send it back it is out of shape. I can see coils touching so there is no even space. I would say it has been used. 

[grsnovi]

The one on the left is the old spring. The one in the package is the NOS spring which is contained in a cardboard ring of approx. 1.125" ID. The NOS spring does indeed have a pre-curved interior curve that approximates the curve of the old spring's arbor attachment end.

[rodabod]

I’d use the new spring. The old one doesn’t look awful, but it is fairly “set”. 
 

If you are lucky then the new spring’s ring will be narrower than the barrel. If not, then remove first and use a spring winder. 
 

The hooking end that wraps around the arbor is annealed and will conform to the arbor of the winder or the watch barrel without intervention usually. 

[grsnovi]

Maybe I'll practice my spring winding using the old spring...

[grsnovi]

Picked up a 2nd identical movement that should answer any questions I might have (including how the spring needs to go back into the barrel).

[JohnR725]

On 4/7/2022 at 10:58 AM, grsnovi said:

t would arrive wound such that I could pop it into the barrel without having to use a winder.

Nice fantasy are having today?

You didn't show the viewing audience something? This is an Elgin mainspring it doesn't have a tongue end sort of it has a T brace end. I have a picture below for those not familiar with what were dealing with. The best way to put these in is with the mainspring winder you wind the spring almost all the way into the winder you leave about an inch out. Then you insert the winder and the little but the spring into the barrel rotate until the T is over the slot. Press it down in the slot and verify that it actually is in their. Then with the back your tweezers or your biggest screwdriver hold the top of the T in place basically F just push it down then you can push the mainspring out of the one. Because you cannot just hope to pop this in place it will never go where it's supposed to and trying to rotated after the fact a lot of luck with that it just isn't I happen. Anything that has a protruding part like a T in any form really has to go in with a Winder.

Then I'm assuming that the right thickness of the spring that you needed? One of the problems with American pocket watch parts Elgin in particular is a part number were referred to a item but often times of common different thicknesses like mainsprings or staffs can have a lot of variations for the same part number she always at the careful of what you're getting to make sure it's right.

[grsnovi]

Thanks @JohnR725 It seems that the #817 was made in three different thicknesses. The one that was in the watch was 0.2mm. (as measured on my "inch" dial caliper) The one that I rec'd is 0.197mm. (I suppose I could be off by 0.003mm) I guess we'll see how it goes. Will report back once I've either succeeded or failed.