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Hi -

I was just wondering if there are any plastic parts in most ETA movements, or in some of the high end movements? I know some Seiko movements like the 7s26 and 36 have plastic parts, and that actually contributes to their toughness - so I'm not suggesting that plastic is bad, or anything of that nature - I was just thinking about the ubiquity of plastic, and wondering if something like a mechanical watch might be made without any - I couldn't remember if the Incabloc system used a plastic piece or not -

As an extention of that question - are there any watches with no plastic? Nothing on the dials, hands, etc?

Thanks for indulging this random question -
 

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Hi -

I was just wondering if there are any plastic parts in most ETA movements, or in some of the high end movements? I know some Seiko movements like the 7s26 and 36 have plastic parts, and that actually contributes to their toughness - so I'm not suggesting that plastic is bad, or anything of that nature - I was just thinking about the ubiquity of plastic, and wondering if something like a mechanical watch might be made without any - I couldn't remember if the Incabloc system used a plastic piece or not -

As an extention of that question - are there any watches with no plastic? Nothing on the dials, hands, etc?

Thanks for indulging this random question -
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Most if not all of my Swiss automatics have steel movement spacers instead of plastic. In contrast, most if not all of my Japanese automatics have plastic spacers.

As far as plastic actually being used inside the movement itself, that is a good question. I strongly suspect that most Swiss autos will use little to no plastic and definitely less than, for example, the Seiko 7sx6 movements.

The Incabloc anti-shock system uses no plastic.

I have a number of watches that use little to no plastic. My best example is probably the Korsbek OE. Most dials are painted on steel. As far as hands, most that I've seen and worked with have also been painted on steel. But whether some form of plastic is used on the top of some hands sets to form outlines, etc., is an open question.
 

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The ETA/Val 7750 has a plastic brake for the chronograph second and hour wheels, as wells as a plastic cup for the second hand tensioner.

The use of plastic really does not contribute to the "toughness" of a movement. The weakness part of any mechanical movement is the balance staff.

The use of plastic in any movement or watch is done for one reason only, despite what they tell you, to reduce the cost.
 

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I have a number of watches that use little to no plastic. My best example is probably the Korsbek OE. Most dials are painted on steel. As far as hands, most that I've seen and worked with have also been painted on steel. But whether some form of plastic is used on the top of some hands sets to form outlines, etc., is an open question.
Just a note here most dials are brass (In fact I have not seen one that was not). Brass is a mue metal and offers magnetic shielding. Steel can be magnetized, even in some forms of Stainless, so it would be a bad choice for a dial.
 

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I bought my first "serious watch" 14 years ago with much less research than I would do now. At that time, I just liked the look and image of it (Fortis Cosmonaut's Chronograph, day & date with 7 moving hands!). It's been my daily beater since then. Smashed the crystal once - dropped from 3 floors up, and countless knocks, shocks and bumps. Its taken it all. Along the way, I learnt more about the movement. Mine was the Lemania5100 - they don't make them anymore - and it has plastic parts and only 17 jewels. A beauty of simplicity and tough to boot.
 

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Just a note here most dials are brass (In fact I have not seen one that was not). Brass is a mue metal and offers magnetic shielding. Steel can be magnetized, even in some forms of Stainless, so it would be a bad choice for a dial.
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Thanks for the correction Samanator. I should have said "painted on metal" to be more accurate. And, you're right about brass being commonly used. But here is what throws me off a little bit. Maybe you can look at these and see what you think.

These are a couple of dials I had laying around. On the left is a Seiko SS Samurai dial and on the right is a Seiko 6309-7290 dial. Here is what I think I see on them. I see potential signs of brass content on the Samurai dial. But on the 7290 dial, I would think there would be more signs of tarnish or fading if alot of brass was used, especially considering the age of the dial. On the 7290, I do clearly see that the dial feet are made of brass as they are a richer brown color.

The Austenitic series of steel grades are non-magnetic. My understanding is that the austenitic grades are known as the 300 series of grades. For example, 310 or 316L are essentially non-magnetic grades. These grades also tend to also have the highest resistance to corrosion. Not a big point because most dials will not be made of this grade.

So, what do we make of these? Could they simply have a zinc coating or just high zinc content? Or some other metal? For example, aluminum?


 

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The 7750 series of movements are the only ones that I know have plastic components. However, these movements have been around for 30+ years and any durability issues would have surfaced a long time ago. I don't think that you have to worry about reliability if a movement has some plastic components.

TZ has a great article, http://www.timezone.com/library/horologium/horologium631672313433425752, on the 7750. From the photos I can only identify two components that are plastic.
 

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Just a note here most dials are brass (In fact I have not seen one that was not). Brass is a mue metal and offers magnetic shielding. Steel can be magnetized, even in some forms of Stainless, so it would be a bad choice for a dial.
Brass does not protect from magnetism.

Mu-metal is a nickel-iron alloy and is very easily magnetized.

The way a magnetic shield works is this:

The "shield" must be a magnetic material (like soft iron or Mu-metal) and completely enclose the part to be shielded. The magnetic shield being and easy path for the magnetic field, draws the magnetic flux into the "shield," this forms a 'bubble' in which there are no magnet flux lines, therefore a shields the interior of the enclosure.

A brass dial would offer no magnetic production.

Do not confuse a magnetic shield with a Faraday cage. A Faraday cage protects from electrical fields and varying magnetic fields, not a static magnet field. Static magnetic fields are what cause watches to become magnetized.
 
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