# Magnetism Marvel?



## eroc731 (Aug 4, 2010)

Ok I'm new and just started laying track, and perhaps this is not a new idea, but after dumping my bag of rail joiner screws for the 2nd time, I uesd a magnet to pick them up....I then discovered that they stuck very nicely to my little Aristo screwdriver as I hunched over those little bugger holes and found I dropped very few screws after that!...a little magnet to the screw driver also helped...

Perhaps this is a homer simpson "DOH" moment but it was rather helpful!

Be well!
Evan


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## Trains West (Oct 4, 2008)

they used to be stainless and non magnetic wonder when they changed


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## eroc731 (Aug 4, 2010)

Scott upon further investigation, I do not beleive these are original Aristo screws....I inherited them when I bought up the garden railroad which is now the basis for my railroad....and I realize that being "ferrous" means they will rust...a touch or realism perhaps but perhaps a pain later on?....


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## steam5 (Jun 22, 2008)

A magnet can come in handy to find a screw which has dropped from a loco or rolling stock, assuming it magnetic. 

I'm sure I saw a magnet mounted to the underneath of a flat car on a thread here, great idea I think.


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## SE18 (Feb 21, 2008)

I wonder if a metal detector can detect something that's non magnetic; and, that small

Dave


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## SteveC (Jan 2, 2008)

Posted By SE18 on 07 Sep 2010 05:39 AM 
I wonder if a metal detector can detect something that's non magnetic; and, that small

Dave Depends on the type and quality of metal detector, and the ability of the person using it.


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## Ironton (Jan 2, 2008)

Not all stainless is non-magnetic. 

A trick I used when buying parts for my sailboat was based on this. Screws at a chandlery are much more expensive than at the local hardware store. So you take a magnet down to the hardware store and check if their stainless screws are magnetic. If they are, move on. If not, they are perfectly useable on the boat.


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## Torby (Jan 2, 2008)

Hmm. They didn't used to stick to a magnet.


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## rkapuaala (Jan 3, 2008)

From physlink.com 
Stainless steels are a very broad group of metals. The name was adopted as a generic term for steel alloys with a minimum of 10.5% chromium. The chromium gives the steel its 'stainless' properties - essentially corrosion resistance. On the surface of the metal, a very thin chromium-rich oxide layer is formed which is inert - i.e. it prevents the steel from rusting. The advantage of stainless steels over plated steels is that, if scratched or damaged, the steel will 'self-repair' as a new oxide layer is formed. In plated steels, scratches in the plate will often lead to corrosion of the steel underneath. 

Stainless steel wrenchIn general, the higher the proportion of chromium, the stronger the corrosion resistance of the steel. In addition to chromium, other metals are added to give the steel particular properties such as strength and malleability. Specifically nickel is used to strengthen the oxide layer. 

As for whether they are magnetic, the answer is that it depends. There are several families of stainless steels with different physical properties. A basic stainless steel has a 'ferritic' structure and is magnetic. These are formed from the addition of chromium and can be hardened through the addition of carbon (making them 'martensitic') and are often used in cutlery. However, the most common stainless steels are 'austenitic' - these have a higher chromium content and nickel is also added. It is the nickel which modifies the physical structure of the steel and makes it non-magnetic. 

So the answer is yes, the magnetic properties of stainless steel are very dependent on the elements added into the alloy, and specifically the addition of nickel can change the structure from magnetic to non-magnetic. 

The following company website has a useful high-level definition of the broad stainless steel categories.


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## Greg Elmassian (Jan 3, 2008)

I went to the following site, and did not see any stainless steel scale humans, ha ha! 

I see your link "slipped" bu a few lines, in the beginning of paragraph 2, the system editor is giving me fits too... 

the wikipedia page on SS is good also. 

Regards, Greg


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## Totalwrecker (Feb 26, 2009)

Posted By SE18 on 07 Sep 2010 05:39 AM 
I wonder if a metal detector can detect something that's non magnetic; and, that small

Dave 
Gold hunters use them all the time and gold is non - magnetic. Flakes and grains are smaller than those huge (by comparison) screws!

John


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## rkapuaala (Jan 3, 2008)

Wow,,, sorry about the Greg,,, I don't know why it didn't paste that link over,,,, maybe I accidentally forgot to hi light it or windows decided for me that I wasn't going to hilight. Gets frustrating trying to copy stuff when the application wants to try to read your mind.


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## Semper Vaporo (Jan 2, 2008)

Posted By Totalwrecker on 17 Sep 2010 09:14 AM 
Posted By SE18 on 07 Sep 2010 05:39 AM 
I wonder if a metal detector can detect something that's non magnetic; and, that small

Dave 
Gold hunters use them all the time and gold is non - magnetic. Flakes and grains are smaller than those huge (by comparison) screws!

John



Aluminium is non-magnetic (unless alloyed with Nickel and Cobalt, "ALNICO"), yet anybody that has used a simple electro-magnetic metal detector will know that chewing gum wrappers with an aluminium foil surface and aluminium pull rings from "pop-top" cans or any wad or piece of aluminium foil will drive the detector nutz from great distances.

In the detector are two high-frequency oscillators (above human hearing frequencies), one at a fixed frequency and one you can adust. The detector combines the output of the two oscilators (called beating them together) and feeds the result to a speaker (possibly through an amplifier) and you hear a tone that is the difference between the two frequencies. You adjust the one oscillator to get two at the same frequency, denoted by the absence of a tone from the speaker.

One of the oscillators is also affected by a coil in the business end of the detector. If a magnetic material is brought near it, that oscillator will change frequency, thus you will start to hear a tone which is the difference between the two oscillators if that coil is brought near a magnetic field.


Non-magnetic, yet electricly conductive material, is detected because the high-frequency fluxuating magenetic field around the business end of the detector induces an electrical current in any nearby conductive material (magnetic or not). That induced current creates a magnetic field which is no different than what is around a magnetic material! Thus it interferes with the oscillator just the same and alters the frequency. The closer together the detector and the induced field are, the greater the effect of altering the frequency of the oscillator, which increases the frequency of the tone you hear. Thus the typical "wow-wow" sound as the detector is swung back and forth near different objects.

More sophisticated detectors can also detect the induced-current magnetic-field (because it will be 90 degrees out of phase with the inducing field) and can thus deterime whether the detected object is magnetic or non-magnetic (ferrous/non-ferrous) and make some indication of which is producing the difference in frequencies.

Relative strengths of these signals can also be used to make guesses whether the material is magnetic, non-magnetic, semi-magnetic, paramagnetic or diamagnetic, which equate to different minerals/elements beyond just ferrous/non-ferrous.


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