The "amagnetic qualities" of U-boat steel

[Crusader]

Information from Sinn, May 2006

All Sinn watches are antimagnetic to 4,800 A/m which is in accordance with the DIN/ISO norm. This antimagnetic rating derives from the high-grade materials of the movement alone. Some watches, like the 656/756/856 aviation watch series and the models 244 and 900, boast a much higher antimagnetic rating of 80,000 A/m which results from a soft-iron inner case.

I was wondering whether the highly amagnetic U-boat steel used in the U-series dive watches affects the antimagnetic rating of these watches at all, i.e. whether these watches have a higher antimagnetic rating than the standard 4,800 A/m. Here is the answer from Sinn (again, summarized and translated inexpertly by myself):

The antimagnetic qualities of the 656 etc. models indicated above derive from the soft-iron inner case which reacts to and deflects magnetic fields. The soft-iron inner case is not inherently amagnetic like the U-boat steel which does not react to magnetic fields at all, much like glass or plastic. Therefore the basic antimagnetic rating of the movement (4,800 A/m) is not increased by the U-boat steel in the U-series watches.

However, amagnetic U-boat steel, because it cannot be magnetically charged, does not affect sensitive navigational instruments, unlike a soft iron case which can carry a magnetic charge (on the outside).

In other words (these are my thoughts): antimagnetic qualities like in the aviation watches prevent the influence of strong magnetic fields on the watch and its accuracy; they protect the watch from outside influences. The amagnetic qualities of the U-series watches work just the other way around, protecting things outside the watch from magnetic interference by the watch itself. This, I might add, is not only relevant for navigational instruments, but also, e.g., for magnetically triggered mines or magnetic detection in general.

[Tim got his boots back]

Thanks Martin for taking the time to solicit the information, translate it and post it up for us.

So....The sub steel case does not help in any way to protect the movement from the harmful influences of an outside magnetic force. But....the sub steel case will prevent outside instruments from the harmful influences of a magnetic movement.

I'm confused, how can the steel be unable to protect the movement but will protect any outside instruments from internal magnetism? I thought the concern should be to protect the watch.

So...if you are worried about your watch becoming magnetized, avoid the sub steel and get a watch with a farraday cage.

[Crusader]

So....The sub steel case does not help in any way to protect the movement from the harmful influences of an outside magnetic force. But....the sub steel case will prevent outside instruments from the harmful influences of a magnetic movement.

I'm confused, how can the steel be unable to protect the movement but will protect any outside instruments from internal magnetism? I thought the concern should be to protect the watch.

The "protection" to the outside instruments is that the watch case cannot carry a magnetic charge, so it does not so much protect them but doesn't pose a risk in that respect.

As far as submarines (and, I may add, underwater military operators) are concerned, they worry most about magnetic detection, hence they tend to use lots of plastic or amagnetic materials lest they trigger a magnetic mine, or set off a magnetic sensor.

In the end, both the aviation watch setup (protecting the watch from outside influences) and the U-boat setup (minimizing the magnetic signature of the watch) are sensible things, and perhaps even mutually exclusive?

The EZM 3, by the way, is built with an antimagnetic inner case and has the increased anti-magnetic rating in a dive watch.

[Tim got his boots back]

I have in front of me, REVOLUTION Magazine, a magazine from Singapore, which was sent to me by Kool Cat, (thanks again Jeff). This magazine is a technical guide to luxury watches with great pics and very interesting articles. In it there is a great in-depth article on Sinn watches and it's associated engineering and technology....and an interview with Lothar Schmidt.

In this interview, Lothar Schmidt was asked:

A few of your watches feature anti-magnetic protection. How truly important is this for daily life?

Mr. Schmidt answers:

Anti-magnetic protection is very important. You may wear your watch without bumping it into anything and one day it may start to lose accuracy. Chances are: your escapement has become magnetized by coming in contact with a magnetic field from your handphone, a sterio speaker or even your computer. That is why in many of our watches such as the EZM3, we feature an anti-magnetic inner case. However, we do not feature this case in the Submarine Steel watches because the case material of these watches is innately anti-magnetic and able to provide protection to the movement.

Straight from Lothar Schmidt's mouth, unless he was misquoted.

[Crusader]

Tim, can you give me no., year and page of the magazine quote, and I'll put the matter to Sinn ?

Many thanks!

[Tim got his boots back]

Sure Martin.

REVOLUTION MAGAZINE - volume four (The Ultimate Issue) 2005 or 2006 I'm assuming
This magazine is issued in Singapore.

There are no page numbers in the magazine. The article is in the Hour Glass presents...TEMPUS pages section.

Please see pics below. You can copy these if you want.

Thanks Martin.

[Crusader]

Thanks, Tim ... give a bit time to prepare this and submit the question to Sinn (as you know I am very busy at the moment with family affairs).

[Tim got his boots back]

No trouble and no rush Martin.

[Crusader]

Just off the phone with Lothar Schmidt (an engineer himself - maybe that goes a long way toward explaining the appeal of "the Sinn Spirit") and here is the official info by Sinn on the antimagnetic rating of the U-series watches:

The U-boat steel is an amagnetic substance, much like titanium, plastic, or wood. It does not affect magnetic fields, so they go right through the material. The movements are antimagnetically protected to 4,800 A/m (they come that way from ETA as a standard), and as the U-boat case does not add magnetic protection, 4,800 A/m is the antimagnetic rating of the U-series watches. Something must have been confused along the way for the report in the Revolution magazine (a common observation when dealing with journalists, I am sorry to say).

However, the U-series watches have very little, if any, magnetic "signature" themselves, i.e. since they consist largely of amagnetic material, they will not disturb magnetic fields as other watches might. Not having such a signature is crucially important for some applications, like working near magnetically-triggered mines, or other sensors or magnetically sensitive instruments. And that's where the advantages of the U-series of watches come into play. (If one desires a higher protection of the movement from outside influences, the EZM 3 is the way to go as far as Sinn dive watches are concerned.)

Adding a soft-iron inner case to the U-series watches, as in the EZM 3 (or in the 656/756/856 and 900 watches) would result in a substantially higher magnetic signature of the watch, negating the particular amagnetic properties of the U-boat steel. Normal 316L steel (tegimented or not) can be magnetized to some degree - but this does not affect the movement, of course, which is inside a soft-iron case. Interestingly, ice-hardened steel (as used in the Damasko watches and the Sinn 756/1st series) can be magnetized to a much higher degree than regular 316L steel. This will still not affect the watches own movement (protected by the soft-iron inner case) ... but it may pose a magnetic risk to unprotected watches lying next to such a magnetized watch!!! B-) :-X

By way of an analogy, the soft-iron inner case of the aviation watches and the EZM 3 works like a "suit of armor", keeping magnetic fields away from the movement, whereas the U-boat steel is like a "stealth coat", providing no extra protection to the watch but making the watch more or less unnoticeable to magnetic fields around it.

Guys, I just love the technological aspect of Sinn watches! :gold