finding out if metal is hard or soft with metal detector

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Rick1-2

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one of my other hobbies is metal detecting so today i was wondering, a little explanation about metal detectors, high end metal detectors have different sounds and numders that come out on the screen the higher the numder or high pitch sound the harder the metal, example gold usually come in with a mid tone while silver a really high tone steel come in like a grunt, so i figured let me use the metal detector see about metal hardness, i've noticed when detecting some chunks of steel sound high pitch while others sound low, so i tried it and sure enough, rebar comes in at a low tone no mid tone whatsoever, mower blades some low some low with mixed mid tone, bed frames and other old chunks of steel that my neighbor gave me, sound mid tone, not saying this shows hard metal but its interesting
 
That is really interesting. It would be really amazing if someone could post or link or create (any voulenteers?) a table that showed a list of different metals and their typical hardness ranges. That would be cool to compare with all the different blade hardnesses that we know about. I think some cannot be measured on the C rockwell scale. I forget the relationship between the numbers on the rockwell scale. For instance I don't think the relationship between numbers is linear as they go up.

Just an idea. What do blades on knives typically run? 47 to 68max?
 
A metal detector does not differentiate between harder metals. It essentially discriminates between ferrous and non-ferrous metals. I suppose highly sensitive detectors could pick up alloy content... but to a degree that is useful to a knifemaker? I have strong doubts.

The higher the tone the more Non-ferrous the metal. Gold and silver are softer than steel . = higher pitch
 
A set of hardness files would be 10x more accurate, and even they'll leave something to be desired. For what a higher end metal detector likely costs, I'd just keep an eye out for a used hardness tester and get spot on results.
 
Measuring "hardness' is much different than measuring "hardenability" or the potential hardness of a given steel. I suspect 52100 would sound the same whether it was fully hardened or dead soft in the spheroidized state
 
Metal detector imposes magnetic field into a metallic sample then "reads" the magnetic properties of the different types of metal. It cant determine specifics of steel alloy. Thats only available thru chemical or spectrum sampling.
 
Short answer - NO.

Longer answer - A metal detector creates a magnetic field. Any metallic object in the field will affect the way the field is shaped. Ferrous objects affect it most. Other metals will allow the field to move through it at different rates. The shape and size of the object, as well as its orientation to the field are the prime factors in the tone, not hardness. If you drive a 12" spike in the ground, the detector will make a certain sound and reading. If you lay the spike flat on the ground, it will have a very different reading. The sounds would be the same if the spike was hardened or fully annealed.
 
I want to find a great metal detector for a beginner. I want to start to look for some coins as I heard this could give you a lot of money
 
Rick1-2 said:
one of my other hobbies is metal detecting so today i was wondering, a little explanation about metal detectors, high end metal detectors have different sounds and numders that come out on the screen the higher the numder or high pitch sound the harder the metal, example gold usually come in with a mid tone while silver a really high tone steel come in like a grunt, so i figured let me use the metal detector see about metal hardness, i've noticed when detecting some chunks of steel sound high pitch while others sound low, so i tried it and sure enough, rebar comes in at a low tone no mid tone whatsoever, mower blades some low some low with mixed mid tone, bed frames and other old chunks of steel that my neighbor gave me, sound mid tone, not saying this shows hard metal but its interesting
Click to expand...
What model/brand detector you have ?
 
DeLinux said:
I want to find a great metal detector for a beginner. I want to start to look for some coins as I heard this could give you a lot of money
Click to expand...
Next time first look in date on last post in topic ...now we are in trouble :)
 
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