Reply To: pocketwatch hairspring.

[chris mabbott]

Hey Bobpat,

Tom has hit the nail on the head, I can only add that replacing a hairspring from one balance to another is not so cut and dry. The hairsprings are matched or vibrated to their balance wheels as shown here Vibrating

If you are replacing the whole balance assembly, from a scrap movement, to a good one, you also need to consider pivot size, balance size, roller jewel size etc. You will have to measure the roller jewel from one movement and size it to the pallet fork gap. Sometimes even the same model/grade can have a different setup.