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Bob Tascione

    Hi Kurtflys,

    If the spring forming technique that we discused in our email exchange the other day didn’t do the trick then the next thing to check would be the arbor hook itself. I’m not sure what type of watch you are working on but if the arbor has a standard hook then make sure that it has enough material to actually hook and hold the mainspring in place. Hooks sometimes become worn, bent, or filed down and may just begin to catch the spring and then pop off as soon as the arbor is turned a little. If the arbor looks good then it’s a matter of forming the inner coil of the mainspring so that the hole in the mainspring presses against the arbor when unwound. If the arbor hook needs to “reach” for the mainsping hole then it’s possible that it won’t latch onto and hold the spring. Often times the spring has been formed incorrectly so minor adjustments will be necessary. Spring shaping can be tricky at first. Things appear to move opposite to what you would expect! It’s a little like trying to back a car up for the first time while looking in the rear view mirror. If you make a couple of wrong bends it can be difficult to correct your mistakes. If possible make some practice bends with an older mainspring on the bench to get a feel for it. After a while it will begin to make sense.
    Hope this helps and maybe others have some tips they can pass along,

    Have fun Kurtflys!