Real antimagnetic watch

[szbalogh]

Want to make an antimagnetic watch with Faraday cage for myself by replacing the spacer ring, dial and adding an additional cover plate.

I was just wondering why watch manufacturer using soft iron shielding material instead of much better Mu-metal or permalloy? 

Anyone has experience with Mu-metal machining? After some reading i know it is soft and can lose its properties by altering its shape. Would it be still better shileding material than iron after.. for example milling and turning?

[Bill_Lewsey]

A Faraday cage doesn't affect magnetism. It will stop radio waves, high voltage-low current electricity, but not magnetism.

Sent from my Hudl 2 using Tapatalk

[rodabod]

They do use mu-metal in some watches such as the Omega 6B/542. You are correct in that it can not be deformed. You must machine it. 

Edited August 2, 2017 by rodabod

[szbalogh]

11 hours ago, rodabod said:

They do use mu-metal in some watches such as the Omega 6B/542. You are correct in that it can not be deformed. You must machine it. 

So i can machine it? I know to keep temperature low, but it wont lose the shielding property? Only if bent? 

Sounds promising since i got now two of those HDD magnet shields

[rodabod]

I only know this from audio engineering where mu-metal is used for shielding transformers. You can not bend it. Even denting it can affect its performance. 

From what I understand, it needs to be machined. Good luck!

[rob1crazydude]

isn't a ROLEX Millgauss watch a real antimagnetic watch?

[vinn3]

high quality stainless is not magnetic,  nor is brass.

[szbalogh]

2 hours ago, rob1crazydude said:

isn't a ROLEX Millgauss watch a real antimagnetic watch?

Not antimagnetic enough    

2 hours ago, vinn3 said:

high quality stainless is not magnetic,  nor is brass.

I want to keep magnetism out of the case. Steel and brass wont block it. 

[vinn3]

block magnetism?

[szbalogh]

6 hours ago, vinn3 said:

block magnetism?

I mean leading magnetic force field lines around the movement. or something

[dadistic]

I'm guessing you either work with MRI machines, or at CERN.  

[szbalogh]

3 hours ago, dadistic said:

I'm guessing you either work with MRI machines, or at CERN.  

MRI-s dont have that high field, up to 3-4 T. I am working with an NMR with 10T. 

 

Edited August 8, 2017 by szbalogh

[dadistic]

9 minutes ago, szbalogh said:

I am working with an NMR with 10T. 

 

No wonder you want shielding!

[WatchMaker]

An alloy like MuMetal certainly has superior magnetic 'permeability' protection at lower magnetic field strengths but this drops rapidly once we're into higher realms; let's say above about 0.6 Tesla. At these higher field strengths I understand soft iron actually outperforms if we're talking about a simple single layer situation comparison. 

In a lab situation the cage type situation you've mentioned would normally consist of various measures e.g. soft iron and separated MuMetal layers to provide maximum protection to what's inside the 'cage'. For a watch manufacturer with ultra limited space then they've had to judge the best route for the protection they're seeking that could affect the watch movement and have decided the best  is an iron core. But remember even the best anti-magnetic watches out there will only cite 10,000 to 15,000 Gauss protection ... so 1 to 1.5 Tesla. 

If you want protection above this you're going to have to get creative. Given the above information you might want to consider a largeish gents watch case ... but with a small (ladies?) movement sourced for its lack of non-ferrous materials. Now you have the space between movement and case to try some creative layering to create the best low-Gauss chamber!

 

Edited August 9, 2017 by WatchMaker

[szbalogh]

4 hours ago, WatchMaker said:

An alloy like MuMetal certainly has superior magnetic 'permeability' protection at lower magnetic field strengths but this drops rapidly once we're into higher realms; let's say above about 0.6 Tesla. At these higher field strengths I understand soft iron actually outperforms if we're talking about a simple single layer situation comparison. 

In a lab situation the cage type situation you've mentioned would normally consist of various measures e.g. soft iron and separated MuMetal layers to provide maximum protection to what's inside the 'cage'. For a watch manufacturer with ultra limited space then they've had to judge the best route for the protection they're seeking that could affect the watch movement and have decided the best  is an iron core. But remember even the best anti-magnetic watches out there will only cite 10,000 to 15,000 Gauss protection ... so 1 to 1.5 Tesla. 

If you want protection above this you're going to have to get creative. Given the above information you might want to consider a largeish gents watch case ... but with a small (ladies?) movement sourced for its lack of non-ferrous materials. Now you have the space between movement and case to try some creative layering to create the best low-Gauss chamber!

 

Many thanks for the comment! I have the case and the movement, my first thought was to replace the spacer ring and the dial with something other than simple steel and brass. I have made some experiments which i will show you in a video if i have time to compile. Compared shileding properties of Si-steel (used for transformers), the sames steel heated to ~800 Celsius, Mu-metal and one that was also heated to the same temperature and finally copper. I was using a small neodymium magnet and measured the field with my tablet. I have found that there is basically not much difference between the mu-metal and the steel and the heat treated ones at this low field. It was up to 3000 Gauss if i put the magnet directly on the tablet. 

I think i will stick to the Si-steel because it is available in large amount (i have one square meter sheet of that , 1.5 mm thick) and it performs just as well like the mu metal. The NMR i am working with is sheilded vertically, it has about 500 Gauss at the sides. Higher field are at the top and bottom openings but i can manipulate there with one hand, changing samples and probehead so that shield up to 3000 Gauss should be enough.   

Did i mention that i want to make enamel on the Si-steel dial?  This is why i checked the heat treated pieces. 

[WatchMaker]

We're in danger of making this a magnetic science thread but I'm certainly very interested if you get time for a video!

I thought from some of the earlier comments that you were into the stratospheric Gauss ratings but with the shielding of the machine you use keeping things down to around 0.3T your approach sounds both interesting and plausible. I did find this thread for you which gives the relative properties of different materials ... http://www.fieldp.com/magneticproperties.html ... now if only you could find some supermalloy! ;-)

I'm getting into making my own dials at the moment so would also be interested in your enamelling procedure as this is something I've considered dabbling in!

 

[szbalogh]

17 hours ago, WatchMaker said:

We're in danger of making this a magnetic science thread but I'm certainly very interested if you get time for a video!

I thought from some of the earlier comments that you were into the stratospheric Gauss ratings but with the shielding of the machine you use keeping things down to around 0.3T your approach sounds both interesting and plausible. I did find this thread for you which gives the relative properties of different materials ... http://www.fieldp.com/magneticproperties.html ... now if only you could find some supermalloy! ;-)

I'm getting into making my own dials at the moment so would also be interested in your enamelling procedure as this is something I've considered dabbling in!

 

Thank You very much for the link! That tablet is not calibrated with a known field, but if i had one i could calibrate it. It measures up to 3000 Gauss, my old phone did it only up to 250. Now i will check the NMR again with the tablet

I did not know but discovered recently that the two main enamel sources are selling now enamel for steel! Did not tried or or neither ordered yet but i will soon. Maybe i will try the enamel for copper tonight on steel