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WWII Gurley compass with magnetized rear sight


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#1 oleake01

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Posted 14 January 2019 - 02:22 PM

Hey all,

 

I recently acquired a WWII Gurley lensatic compass to add to my collection, but was very surprised to find that the metal of the rear sight has been magnetized! When the sight is folded down to the glass surface, the floating dial snaps up to the inside of the glass as if attracted to the sight and only moves back into its original position when the sight is brought up and away from it.

 

The dial itself has also been having some problems pointing due north, which I'm wondering if it might be due to the sight being magnetized and confusing the needle.

 

Any ideas on how to de-magnetize the sight without screwing up the rest of the compass?

 

Many thanks!



#2 Blacksmith

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Posted 14 January 2019 - 05:37 PM

I dont know that you want to demagnitize it, as I believe it is by design.

I will defer to the compass experts, but believe that function is designed to protect the compass moving parts / points of friction while it is not being used.

I have seen some with sliding buttons as physical locks, and some with this snap-to feature.

Edited by Blacksmith, 14 January 2019 - 05:37 PM.


#3 oleake01

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Posted 14 January 2019 - 06:30 PM

I dont know that you want to demagnitize it, as I believe it is by design.

I will defer to the compass experts, but believe that function is designed to protect the compass moving parts / points of friction while it is not being used.

I have seen some with sliding buttons as physical locks, and some with this snap-to feature.

 

That's fascinating! I didn't know that. My Superior Magneto Corp compass doesn't do that as far as I can tell, which is why I was so surprised when the Gurley did.

 

I guess the question now is why it's struggling with pointing north and how that could be fixed?



#4 doyler

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Posted 14 January 2019 - 07:20 PM

I dont know that you want to demagnitize it, as I believe it is by design.

I will defer to the compass experts, but believe that function is designed to protect the compass moving parts / points of friction while it is not being used.

I have seen some with sliding buttons as physical locks, and some with this snap-to feature.

 

+1

 

some compass's  have a lever that's activated to keep the needle from moving once the lid is closed.You will see it on the pocket watch type issue compass for example.



#5 Blacksmith

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Posted 14 January 2019 - 07:22 PM

Hard saying. If you’ve been trying it indoors, take it outside and try it maybe. I’ve seen where interior electrical wiring will create funky magnetic fields.

#6 doyler

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Posted 14 January 2019 - 07:28 PM

Hard saying. If you’ve been trying it indoors, take it outside and try it maybe. I’ve seen where interior electrical wiring will create funky magnetic fields.

 

Yeah.Some older homes or buildings have metal mesh/screen for under lay of the plaster or concrete...Im not to wear a tin foil hat near the micro wave any more.... :blink:



#7 Dogsbody

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Posted 15 January 2019 - 08:24 AM

I don't think the rear sight is magnetized. When I touch the rear sight on my example with something made of iron it doesn't 'attract'. I believe it is some kind of mechanical operation. When you push the rear sight down very slowly you can feel some resistance at a given point and when you push through that resistance the dial will flip up.

 

Rene



#8 Blacksmith

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Posted 15 January 2019 - 08:30 AM

You are correct. That mechanism is generally called a pin lock. As I mentioned, it is to protect the moving parts of the compass when not in use.

I don't think the rear sight is magnetized. When I touch the rear sight on my example with something made of iron it doesn't 'attract'. I believe it is some kind of mechanical operation. When you push the rear sight down very slowly you can feel some resistance at a given point and when you push through that resistance the dial will flip up.
 
Rene




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