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Dimpled plates, when did they begin?

Willie X

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Feb 9, 2008
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I remember a thread that asked 'why dimpled plates'. I don't think it ever came to a final conclusion?

I am wondering when 'dimpled plates' got started?

I thought it was around 1960 but I'm working on what might be a 1932. :???:Junghans with nicely dimpled plates.
Something tells me that my dating is off about 30 years here? :)

Guess I'm actually asking two questions:
When did dimpled plates begin? And, is this clock from September 1932?

Thanks in advance. Willie X

OK, lots of answers came up at the bottom of this post but nothing when I used the 'search' feature prior to writing this thread/question. Oh well.

IMG_20210921_181934~2.jpg
 
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new2clocks

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Willie,

There were dimpled plates as far back as the 1930s and possibly a bit earlier.

The Junghans movement that you have shows '329' on the backplate. This could be a date code of March, 1929. However, only movements made in 1928 have been documented to use the dating protocol of [month ... two digit year]. For the year 1929, the documented dating code was reversed - [two digit year ... month].

OTOH, I do not believe that there have been any documented movements from the year 1932. It is possible that this movement was produced in March of 1932.

So, either way, perhaps this is a date code that has not yet been documented.

Regards.
 
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Willie X

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Certainly more questions than answers.

John mentioned 1932, 33 and 34, so it was a thing back then, long before I thought it was.

This movement (photo) just doesn't look 90 years old. Maybe it's the 'dimples'. :)

Willie X
 

tok-tokkie

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I seem to remember that the dimpling was applied to stiffen & maintain flatness. The dimples displace material placing the outer dimpled layer in compression. So the plate has compressed outer layers &, consequently, tensile forces in the intervening inner layer.
Same as for toughened glass. The hot glass is cooled on the outside by a "shower" of cool air jets so it rapidly cools below the glass transition temp & becomes stiff. Subsequently to inner glass cools & contracts giving the same end result = compressive stressed outer skin & tensile stressed inner body. The pattern you see on toughened glass when you are wearing polarized glasses is the pattern of the air jets.
I repeat - that is my memory of the explanation - but my memory is not what it used to be.
 

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