Measuring Mainspring

[david carlson]

I am needing a new mainspring for the clock I am working on. I tried to unwind the old one to measure it, but it is hard to get the last 5 wraps straightened. Can I guess at the last few inches or do I need to get a good grip on it and get it unwound. Is there an easy way to get it unwound with cutting your fingers off?

[willofiam]

Hi David…I was just measuring mainsprings this morning too. A good trick especially with small mainsprings, though this works great with any size, is to lay the mainspring on a flat surface and tape, tie or clamp one end of a string to the outer end of the mainspring. Then tuck the string between the coils as you work your way to the center. When you get to the center of the mainspring cut off the string at that point and lay the string out for a measurement. Will get you pretty close. Have a great day, William

[dave booth]

Dave – Don’t forget to measure thickness (strength). That is moderately critical. Whenever I have to do that, I anneal enough of the end to make certain I can get it straight, so that my measurement is not across the rise in the arc. To anneal it, just heat it to a dull cherry red, and allow it to cool slowly. If you have trouble with it cooling too fast, lay it on some sand in a pie pan, and heat the whole shebang. If need be, you can even do that on the kitchen stovetop.

[david carlson]

Thanks for the help.

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