Elgin 626 movement mainspring choices

[WilliamTK48]

Hello everyone,

I recently purchased a watch with an Elgin 626 movement from the early 1950s. I was able to disassemble the movement and give it a clean, but discovered that the mainspring had become weak and was no longer capable of giving consistent power.

The spring has a hole near the end which fastens to a hook inside the barrel, as well as a bar with a tooth that sticks through a slot in the top and bottom of the barrel. I'm afraid I don't know the proper term for that.

When I looked on the Ofrei website, it appears I need a spring for a 15/0 Elgin, Grade 557 spring in white alloy. There are four different choices, each with a different strength measurement: .091, .102, .107, and .114. 

Assuming I've found the correct spring, which strength should I order for this watch?

Thank you,

-William

[dadistic]

Use calipers to measure your existing spring, those strength measurements are in millimeters. 

[WilliamTK48]

I ended up ordering from the McCaw Co. in Toledo, OH. They only had one spring choice on their inventory. It's white alloy, Swiss made and wound up in a blue aluminum washer labeled 15.00. The difference between the new and old springs was like night and day. Once the new spring was wound into the barrel, I had to dip and demagnetize the hairspring, but now it seems to have settled into a steady rhythm and is matching my other pre-war Lord Elgin for accuracy.

Sadly, the tiny second hand was a casualty during this. It didn't seem to be sitting straight on its arbor, and my efforts to adjust it broke the hand off. The arbor's fine, but the little hand isn't. Maybe I'll find a donor movement with the hand still intact and make a swap.

[dadistic]

According to Ranfft, the sub second arbor is .20 mm

http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&1ranfft&b&2uswk&Elgin_626

You can find various small hands at Otto Frei, this page lists hands for chronographs and sub second hands that fit a .20mm arbor.

https://www.ofrei.com/page966.html

Cheers!

[WilliamTK48]

Thanks for that tip, dadistic.

Dr. Ranfft's website is a great resource, and I'm embarrassed to admit that I didn't know how the hand measurements worked. 

So now it's a decision between around $3US+shipping for a new hand, or somewhere between $10 and $20 for a parts movement with the hand intact. I may go that route for the spares, and another movement to tinker with. The price of gold must have people selling their watch cases for scrap and orphaning the movements.