Compass and steel

Ok, this is for all you scientific folks and us ordinary users. IF you have a small button compass such as the one on the Firesteel tubes, AND have a loop to hold it on your knife sheath, the compass will always point to the knife, right? Ok If this is so, will it have any affect on the compass when removed from any influncing metal, STILL POINT to magnetic North? Seems to me that it should, but will it?

I do believe so, the steel isn't changing the polarity, just adding something other than the magnetic pole to swing to. As soon as you remove that influence, it should swing around to north

MOK, that's what I thought, but then again I thought that over the long haul it may change it. Perhaps I should have asked the same question about the military lensatic compass. You know the one that "Freezes" the needle when you flip the little magnifier arm down IF you flip it down with the needle NOT pointing to north.

I've never heard of that problem

But I don't know much

Haha, do any of us really?

naw, but some know more than others

Randy, send me your set-up and I will try an experiment or two with it!

Hi,

To demagnetise metal you have to scatter the orientation of the magnetic fields of each individual atom.

This can be achieved by a few methods.

Heat the metal up past its Curie point.

Hit the metal multiple times really hard.

Move an opposing magnetic field against the metal's magnetic field multiple times. This is usually done with a Degaussing unit which cycles a strong magnetic field 50 or 60 times a second against the object to be demagnetised. If you've ever seen a tape wiping machine (for old magnetic tape) then this is Degaussing unit.

Now since the compass is able to float - it always links its magnetic field to the opposing field of the steel - so it doesn't have an opposing field forced against it since it can just move with the field. The floating action also acts as a shock absorber so impacts don't affect compasses. The only thing you have to worry about is heat. The Curie point for iron is about 700 Celsius - about 1300 fahrenheit.

I hope this helps.

Cheers,

Harley.

Heck of a first post harlequinn.
I've read where knife makers heat the steel up to where it loses its magnetism as part of the heat treating iirc.

Welcome to the Yard & happy new year.

Harlequinn, WELCOME TO THE YARD! It's a friendly place with a lot of nice folks. A lot of, unlike me, are pretty smart and can give very informative answers on a variety of subjects. I see that you as well are very well versed. Keep up the good work, don't be shy.

Thanks myketheknife and SkunkHunter - it's nice to be welcomed.

Happy new year.

Welcome to the yard.
We are a pretty relaxed bunch here.
Take a minute to read the rules and have fun.
The death chat can be very entertaining at times.

Harley - Howdy and Welcome to the Scrap Yard! <img src="/ubbthreads/images/graemlins/grin.gif" alt="" /> <img src="/ubbthreads/images/graemlins/thumbup.gif" alt="" />

Thanks coyotebc and Private Klink.

I've done a little testing in regards to compasses and steel.

Using a regular orienteering compass I've found that large iron based metal loads adjacent to the compass can completely skew the north point - as far as 180 degrees. I used my refrigerator as the metal load about halfway up. If you place the compass above the the metal load it still points north but with a varying degree of error (up to 15 degrees in my case). It may be that there was an electromagnetic field generated by the compressor or such skewing my results. If anyone has a large steel beam to test this against I'd be interested to see the results.

Testing the compass against a knife it gives a slight error but it will still be pretty much north. The error is greatest at the tip and heel of the knife (where the magnetic fields are strongest).

As above it won't ever permanently change the magnetic field of your compass but perhaps you should test to see the error it induces both with the knife in the sheath (there should be no effect with the knife out) and the position the compass has on the sheath with the knife in (the tip and heel of the knife produced the strongest error).

These are of course just anecdotal views and not any thorough scientific testing - but it's a pretty good starting point for further investigation.

Cheers,

Harley.

Harley: Thanks for the input! Just seemed that the compass should be skewed at least slightly by the blade from sharpening all the time.