measuring the main spring

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  • #49453
    • Topics Started: 22
    • Total Posts: 60

    Can someone explain the use of the main spring measuring devices please and how to equate the results to the main spring packet. I had to go through my complete main spring collection, over 50 springs, to find the right size spring for a Harley wrist watch I am renovating. The guages read 10 thick and 4 wide. on top of all this, I put the mainspring down and could not find the barrel. I thought I put it in a spring packet when I cleaned up so I went through all the packets again trying to find the barrel with no luck. Looked all over the place still no barrel. I sat back at my bench looking at the spring thinking were the hell is the bugger. I picked up the spring and bugger me the barrel was sitting under the spring. I need another hobby I think, I spent another hour and a half looking for a winding stem for it, I have to put my stems in one place I have numerous draws and little containers every where with stems in them, another job for later.

    chris mabbott
    • Topics Started: 119
    • Total Posts: 1525

    Personally, I’ve never used one (bad, bad), I use a vernier, measure thickness, width and length, and of course, the anchor end must match, or it can be fine tuned to fit ;)
    There is a rule of thumb guide for the amount of spring that occupies the barrel, but I can’t for the life of me remember how much it is right now.. I think it’s in the Chicago School of Watchmaking manual, which provides an excellent, if not one of the best studies on mainsprings..

    david pierce
    • Topics Started: 90
    • Total Posts: 1360

    A company called LULU PUBLISHING sells a hardbound edition of the CHICAGO SCHOOL OF WATCHMAKING. The course has a fairly comprehensive coverage of metric and Dennison mainspring measurements, shows how to use a Dennison gauge, and has conversion charts as well as mainspring charts for various watches. Tom posted a link to purchase the course (book) a few months ago and it is buried somewhere in the previous posts.

    • Topics Started: 75
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    just type in “chicago school of watchmaking” in the search and you will get everything you need about the book. Toms lead to it thru lulu was great….I bought one also, not a bad price either. I think someone posted a index for the book also but I cant remember….need more java this mourning. William

    bernie weishapl
    • Topics Started: 58
    • Total Posts: 1218

    Here is a link to the Chicago School of Watchmaking.

    Looks like it is $65. I found a link on the NAWCC forums that you could download and burn to a CD that was free.

    • Topics Started: 22
    • Total Posts: 60

    Thanks Bernie, the 700 page Chicago School of Watchmaking (Complete Watch Repair Course in ONE BOOK) looked to good to pass so I bought it. can’t wait to read it.

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blondfellowmeasuring the main spring