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28-11-2019 17:03:20  #1

Mainspring - how tight?

Hi, I have today had the unfortunate business of having the drawbands on 2 machines spinning back and around their respective mainspring hubs while I did some maintenance (sometimes we just have clumsy days). Anyway, I have rewound the mainsprings and the drawbands have good tension again. But this got me thinking, how tight is too tight? And how much "over-tension" can 50-year-old mainsprings take?

Obviously if the carriage is flying to the left or skipping spaces when typing, that would be a sign, but I was wondering if there was a better method while actually winding the mainspring to begin with. Thanks in advance for any insight.


28-11-2019 18:17:32  #2

Re: Mainspring - how tight?

Hi Typeitup

If memory serves me correctly, correct mainspring tension should give about 2 pounds (0.9kg) force on the carriage at mid point with escapement disengaged (carriage release held with elastic band). Hope this points you in the right direction,



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