Reply With QuoteIt would gain time if magnetised not loose it.
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A friend has a 5-year-old Submariner no-date which he bought new. It's started losing time. About a couple of minutes a week. He has had an x-ray recently so my initial thoughts were that it must be magnetised. I've told him to buy a cheap demagnetiser on ebay but have now thought about it and remembered the "parachrom hairspring" and thought that was un-magnetisable (yes I just made up that word). Am I wrong? I don't want to send him down the garden path.
Also, if I'm not wrong can anyone recommend which demagnetiser to go for please?
Thanks
It would gain time if magnetised not loose it.
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Last time I checked x-rays won’t affect a watch. If it were an MRI different matter. Perhaps due a service?
^^^ they don't even ask you to take your watch off for an x-ray, but sure as heck do for an MRI.Originally Posted by MartynJC (UK)
first thing to do if you suspect magnetism is to find a small compass and move it around on the case. Below pic shows the effect magnetism has (top compass is pointing the wrong way)
I'd think any ebay demagnetizer will be fine. They don't actually demagnetize the watch, but instead apply a chaotic magnetic field which means there's no overall magnetic alignment. This is the state all steels are in before they get 'magnetised'
Think you need to be careful with the demagnetiser though, cant' using a demagnetiser on a watch that is not magnetised damage it?
This (spelling fixed).
When I first saw that pic, I thought it was the latest offering from MB&F! : )
Be very careful with the coil based demagnetisers on eBay. You have to use them correctly or risk magnetising the watch or damaging the hairspring.
I would be surprised if magnetism is the issue anyway. The new hairsprings are bombproof.
An MRI scanner has a very large (electro)Magnet to enable the Resonance Imaging.
I bet you are right about the service though :).
Overall effect is demagnetisation.
: - )
yup
Not sure about the compass, that'll detect magnetism in the case, but what if the hairspring (or other movement parts) are magnetised but the case isn`t? The tiny magnetic field around the hairspring would be shielded by the case in such a scenario.^^^ they don't even ask you to take your watch off for an x-ray, but sure as heck do for an MRI.
first thing to do if you suspect magnetism is to find a small compass and move it around on the case. Below pic shows the effect magnetism has (top compass is pointing the wrong way)
I'd think any ebay demagnetizer will be fine. They don't actually demagnetize the watch, but instead apply a chaotic magnetic field which means there's no overall magnetic alignment. This is the state all steels are in before they get 'magnetised'
The effect of demagnetising a watch that's been affected can be dramatic, I`ve see amplitude shoot up from 215° to 290° and the rate fall by over 1 minute. Sometimes a movement will be slightly affected, it may seem to be running OK, but demaging it will increase amplitude by 10-15° and alter the rate slightly.
Never ceases to amaze me how they become magnetised thesedays, but they do.
As all (? as I don't know what alloy Rolex use) hairsprings have something in the region of 50% nickel+Iron content in their alloys, then they can become magnetised. But to do so presumably the magnetic field will magnetise the case to a greater extent, as it's around 80% iron+nickel. Based on this logic I'm not sure how you'd get the hairspring magnetised but not the case. Materials science isn't my greatest strength though so I stand to be proven an idiot.
AFAIK Rolex use 904L stainless steel which is non-magnetic and as such will not shield the movement (including hairspring) from magnetic fields (same for 316 SS).
904 and 316 are magnetic though, as both alloys are mainly iron and nickel
Being mainly iron and nickel does not make them magnetic: - https://www.finetubes.co.uk/products...904-wnr-1-4539
Edit:- Try a magnet on your saucepans and cutlery. Most will not be attracted.The grade [904L] is non-magnetic in all conditions ...
Last edited by Kingstepper; 21st January 2019 at 17:41.
I`ve forgotten most of what I learned about magnetism in the distant past, I used to know these things but it's a long time ago!
Suffice to say that modern watches do get magnetised and we don`t fully understand how. The silicon hairsprings should help, but most watches don`t have them.
As for the OP's question, I don`t think the watch is magnetised.....maybe it's been dropped or had a hard knock? Surprising how owners forget these incidents!
Correct,
I don’t think that’s correct.
I thought that usually they gain time but they can also lose time.
I don't believe they loose time.
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OK. Let’s make this more emphatic. x-rays do not magnetise watches. OP - your friends watch needs a service , simple.
(I could be wrong)
Last edited by MartynJC (UK); 21st January 2019 at 19:36.
This was worth an experiment!
316L stainless steel, commonly called surgical or marine grade, but also knife and fork grade. Two 316L spoons with a magnet. I was going to try the 'stroking it umpteen times with the magnet to magnetise them' test, but chickened out on the grounds that my wife would probably be a bit annoyed if she found all the cutlery inexplicably sticking together.
Agreed though the the OP probably dropped his watch.
Interesting, tried it on my saucepans and not attracted though cutlery is. All items marked as '18/10' which is the same as 304, not 316.
Interestingly knife blade was highly magnetic, handle, spoons and fork much less so. Although 304 is inherently non-magnetic can become magnetic by cold-working. Presumably how cutlery is manufactured?
I'm thinking of magnetising the forks one way and knives the other way now. then when the kids put a knife in the fork tray it'll suddenly jump back out and my ocd 'sleeping with the enemy' tendency will be satisfied.
The question, as I see it, is whether the watchcase can be permanantly magnetised by the influence of an external magnetic field. I’ve done a bit of homework to refresh my memory, and everything I read suggests that 316 and 904l stainless steel will not be permanantly magnetised, neither exhibit ferromagnetic behaviour. There’s a difference between a material being weakly attracted to a magnetic field, and becoming magnetised, lets be clear on that point, I think that’s where confusion can arise.
It is my belief, unless someone can provide evidence to the contrary, that the problem of watches being affected by magnetism is chiefly related to the hairspring becoming permanantly magnetised owing to the influence of an external magnetic field. The case itself does not become permanantly magnetised; the process of demagnetisation effectively reverses the permanant magnetisation of the hairspring and any other ferromagnetic components, thus allowing the watch to function correctly.
A magnetised hairspring will operate with reduced amplitude and increased rate. I think this is caused by the coils repelling each other, can’t be certain on this point but it makes sense.
I’m still surprised that modern watches become magnetised, I would expect the typical heavy steel cases to shield the movement, but that doesn’t seem to happen. If anyone can explain this I’m keen to hear an explanation.
All of my pans are magnetic - otherwise my induction cook-top couldn't work. All of my cutlery is too.
I would assume that pans you have that are not magnetic are made of aluminium or ceramic.
904 stainless steel absolutely is magnetic.
This is not entirely correct. The crystal structure of steel is usually something called a martensite which is box centred cubic and it is this which gives rise to its ferromagnetic behaviour. But in 316 etc. the crystalline structure is forced to be an unstable face centred cubic structure by the the inclusion of nickel, manganese and other stabilising additives. This produces a structure called austenite which is non-magnetic. The difficulty arises because austenite can change to martensite when heated, welded, bent, machined or stressed. Sometimes the change can even happen spontaneously. So while 316 and 904L might not ordinarily be magnetisable, it is not always so. It is also worth noting that not all stainless steels are austenitic. Some are martensitic and therefore ferromagnetic.
Wow, are you a metallurgist? I learned a fair amount about stainless steel back in the days when I had a proper job, but I don’t recall ever learning about the crystal structure of it. Face- centred and box- centred cubic?.........I always struggled with this when studying inorganic chemistry, can’t say any of it proved to be any use either.
So why do watches become magnetised in normal use, and do the cases themselves actually become magnetised? That’s the question we’re struggling to answer.
I understand how stainless steel can be weakly attracted to a magnet, but does the temporary magnetisation of the case affect the movement by causing the hairspring to be affected? I would’ve thought the case shielded the movement to a large extent, maybe I’m wrong? One of the worst cases of a magnetised movement I’ve come across was a Seamaster Pro, that’s got a thick steel case and an aluminium shield inside the caseback, but it was still heavily magnetised.
I’ve never tried to deliberately magnetise a watch, I’m tempted to have a try.
I magnetised my PRS 25 by laying it next to a rubber band I used to wear that had a magnet within it. Its so easy to do. I took it my local watch repairer he had another jeweler work on it, and its been fine since.
Appreciate your comments, Groundrush, you clearly know your stuff. I did a chemistry degree many years ago and worked for years in the chemical industry, I picked up a fair amount of knowlege re. materials, engineering, and plenty more but I’ve forgotten a lot too. I was Jack of all trades in many ways.
The concept of magnetism isn’t so easy to get your head around, have to admit I’d forgotten most of it.
The cheap demagnetisers seem to work OK, which is a good thing. I demagnetise movements out of the case, in future I’ll give more attention to demagnetising cases too.
Brilliant! That would be a very funny trick to play on your kids !
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