French Spring Thickness Gauge

Discussion in 'Horological Tools' started by THTanner, Feb 23, 2019.

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  1. THTanner

    THTanner Registered User
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    This was listed as a spring thickness gauge from France.

    The large cut outs around the edges run from "43" -which is 5.1mm down to "000" which is about 0.75mm

    The steel strip runs from a much smaller "0000" "000" "00" "0" then 1,2,3,....12

    Does anyone know what these markings actually show in terms of wire or strip spring thickness?

    SpringThickness.JPG
     
  2. wefalck

    wefalck Registered User

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    In the old days the French watchmakers used the length unit ligne, which is 2.26 mm. There was also the point of 0.188 mm. However, both units don't seem to tally with the numbers on the tool.
     
  3. Dave Coatsworth

    Dave Coatsworth Forums Administrator
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    Feb 11, 2005
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    This is a Dennison gauge for measuring the width and thickness of watch mainsprings. The conversion table between Dennison units and centimeters is attached below. Note strength = thickness.

    DennisonConversion.jpg
     
  4. THTanner

    THTanner Registered User
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    Thanks so much - I would have never guessed Dennison and the seller had no idea.
     
  5. richiec

    richiec Registered User
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    I am surprised there were no markings on the opposite side as well, the one I have is marked metric and Dennison.
     
  6. THTanner

    THTanner Registered User
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    backside is just polished brass on this one - - maybe a repro
     
  7. Dave Coatsworth

    Dave Coatsworth Forums Administrator
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    It looks legit. Not all of them have metric measurements on the other side.
     
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  8. Dushan Grujich

    Dushan Grujich Registered User

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    #8 Dushan Grujich, Feb 25, 2019
    Last edited: Feb 25, 2019
    G'Day!

    It is quite possible for the gauge to be by any of the standards used in Europe. For example, I have several of the gauges, Robert, Montadon, Dennison and a combination of Metric on one side and Dennison on the other. The list of the standards is by no means exhausted as there are many more than just the few mentioned, each mainspring manufacturer used his own standard. In one of his books, Jendritzki has given a table with sizes of Robert and Montadon standards as related to Metric.

    BTW I don't use any of them, I use only my micrometer screw to measure the mainspring when needed.

    Cheers, Dushan
     
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  9. Dushan Grujich

    Dushan Grujich Registered User

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    G'Day!

    I have scanned page with the cross reference table Robert, Montadon to Metric.

    Cheers, Dushan

    Jendritzki Mainspring table.jpg
     
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  10. THTanner

    THTanner Registered User
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    thanks so much - great documentation
     

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