Steel affecting compass?

dougo83

dougo83

Joined
Feb 28, 2008
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Ok...for the second time I have had a compass that I keep in a pack with knives and other metal gear become disoriented. The first one ended up being a full 180 degrees off. The second one was about 90 degrees off. Luckily, I checked them to sun position and my truck compass before I set off.

So...what the heck is causing this problem. Neither one of the compasses were especially expensive, but not the cheapest ones on the market. I am out of ideas.
 
I carry one or two ice axes on my backpack and never experienced such
amount of offset so far. My axes are slightly heavier than 1lb. and fully
made of steel (HTed 5160). Sorry, no idea for 180 deg offset.
 
Take the compass out and away from your metal gear. Then mov e each of your gear accross the compas. If it disturbes the compass it might affect it. I had a similar problem. My swiss tool affected the compass. Since then I keep them seperate and have not experienced the problem again.
 
I think that maybe some of your gear might have been magnetized. Chances are, if a compass gets disoriented like that, it's caused by an outside magnetic field. Steel will cause a compass to deviate, but will generally not cause it to get permanently disoriented.
Mind you, i've no degree in such things, and only speak what i find logical in my own head.
I hope someone more knowledgeable can chime in, and set this thing right.
 
You may already know this but I think you can correct one that's been magnetized and off by 180 degrees by passing a magnet back across it.
 
It's not uncommon to have knives whose blades are magnetized ! In addition you shouldn't use a compass near any steel magnetized or not.
 
Austenitic stainless steels are about the only metals that I know of that will not affect a compass. Most other steels that are ferritic and martensitic steels will usually exhibit a strong pull for a magnet and all it actually needs to do is to warp the lines of magnetic flux to affect the compass.

KR
 
Be careful about checking your compass in a vehicle, or even near one. The Iron mass in the car as well as the electrical fields in a vehicle will affect the readings enormously.

As stated above take any metal objects from the pack and pass them close to the compass if the needle follows the object keep it away from the compass.

It also makes a difference if the compass is one of the inexpensive ones on the market. Many of the economical ones coming out of china seem to develop serious problems quickly.

I use one of the Cammenga lensatics and have had zero problems with it. But I can take off my glasses and the needle will follow the frames if they are held close to the compass (1 inch or so) though they do not affect it in normal use.

Get at least 35 feet from your car and see how it reads then.
 
Small pieces of steel will in fact affect your compass. If you have a ferrous belt buckle, that will throw your compass off by a few degrees if you hold the compass right up near it.

Not sure what would cause a compass to be permanently off by so much as what you're experiencing.

Ferrous items that sit still for very long periods of time will develop a slight magnetic field, as the iron atoms over time align themselves with the earth's magnetic field. Something to keep in mind. There are pieces of equipment on my parents' farm that have been sitting around for decades, and they will throw a compass off.

Sounds like your compasses are either poorly built or were exposed to a significant magnetic field. Marthinus' suggestion is what I'd probably do. You should also check where you're storing your bag, especially if it's there a lot.
 
To have a permanent error stumps me. Proximity to metal is temp., as I am sure you already know. Doesnt really answer your prob, but how about buying a really good compass.
 
My GEC trapper blade, move the compass needle like a magnet. Metal does affect the magnetic field. I used to hike on a Dormant volcano, Compasses were useless because of the iron ore levels in the rocks.
 
I agree with the folks that say the metal in your car will effect your compass, while you are near it.

When I was teaching underwater navigation, I would send the advanced students on a path that would take them over an auto that was submerged to see how they handled their compass being off. It almost always through them off course.
 
I should have also mentioned this also. The ARMY had a table of distances that you should be away from items for your compass to read correctly. Clearly they know that metals disturb compasses.

I looked it up. Here is a little sample but I remember a more extensive listing in one of the other FM's.

Manual page 2-2

Magnetic Fields Minimum Distances(meters)
High tension powerlines 60
Field guns 20
Vehicles (wheeled or tracked) 20
Telephone and telegraph wires 10
Barbed wire 10
Machine gun 3
Rifle, pistol 1
 
One other question that may be involved. Does your compass have an actual needle, or is it a disk type of compass that spins?

KR
 
wildmike said:
Be careful about checking your compass in a vehicle, or even near one. The Iron mass in the car as well as the electrical fields in a vehicle will affect the readings enormously.

Get at least 35 feet from your car and see how it reads then.
Click to expand...

This would be my advise aswell. Sitting in your vehicle will absolutely throw your compass way off with all the electrical wiring buzzing around you. Your compass usually will be off near any type of civilization IE inside or near your house or other outbuildings with electric currents running through them.
 
I got a thread somewhere in here on things that threw off my compass and by how many degrees. Things like rocks, knives etc, ...i cant find the thread though
 
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