Non magnetic knife...

[alanganes]

So this is sort of a thought experiment as much as something I actually plan to make, but just wondering what the think-tank might come up with here:

Talking with a friend the other day the subject of non-magnetic knives came up. This would be for a pocket/work type knife preferably a folder. A quick search on the web turned up surprisingly few options. There are some specialty fixed blade knives made for scuba divers (does not screw up your compass) and people who clear landmines (does not get you blown up) both of which are very expensive and not folders.

The most workable option seemed to be this one by Boker Plus:

http://amzn.com/B004NS9PVK

and another similar offering by the same company:

http://www.amazon.com/dp/B003XA3CZE/ref=cm_sw_su_dp

They both use a ceramic blade and either titanium or carbon fiber handles. Both seem to get mostly OK reviews, so I ordered one of the titanium body ones.

While this solves the magnetic part, I have mixed feelings about the ceramic blade due to the susceptibility to chipping under general "working on stuff" type usage. I do know enough not to use my knives for prying things or doing other such dumb stuff but I also don't baby them. They get dropped, the edges occasionally get dulled when cutting tie-wraps or whatever against a hard surface, etc. Not a huge deal with a standard blade as I just touch up the edge and it's good to go. Not so sure that will be the case for the ceramic blade.

Having never used a ceramic blade I may be worrying about nothing here, time will tell. But it got me thinking, is there a good non-magnetic metal that one could make a decent blade out of for this sort of usage?

Thoughts??

Thanks,
Al

[EdK]

I believe there are some stainless steels that are non-magnetic. That would be an interesting project.

Ed

[alanganes]

True, I have worked with non-magnetic stainless of some sort (I don't know what type it was, long time ago) but not for something that was designed to be sharpened to an edge. No idea if it would make a decent blade.

[PixMan]

I think the reason that the "magnetic" stainless steels such as 416, 420, 440F, 440C and other martensitic and ferritic stainless steels are so often used in knife making is because that carbon content adds the ability to be a little harder and maintain the sharp edge. An austenitic 300 series stainless (303, 316, 321, 347) just don't seem to have the hardness needed. Looking at the tensile and yield strength values for the 400 series versus the 300, it's no contest. The 400 series stuff is quite a bit stronger and can get much harder.

In ceramics, the hardness is always there, but so hard it's downright brittle. When I worked for Norton Company in their High Performance Ceramics Research & Development Center (Northborough MA) there was work going on to find new materials for knives. It's BIG business in meat packing here to have your knives in the plants, and they went after it with Transformation Toughened Zirconia. That ended up being the overall winner, beating many variations of silicon carbide, aluminum oxides and SiAlON. You could actually get a bit of a bend in the TTZ blades. The other materials had better properties under heat, but knives never see elevated temperatures.

I have no idea if they sold the ideas off to the big knife makers, got it stolen, or stole it themselves but it seems to be the material of choice to this day.

[alanganes]

So I finally returned home and got a look at my new "non magnetic" pocket knife. I was disappointed to find that while it is a pretty nice knife, it is definitely NOT non-magnetic overall. The ceramic blade and the titanium frame parts are indeed non-magnetic, but the pocket clip, the stud on the blade, and the pivot parts are all plenty magnetic. And that defeats the entire reason that I bought it.

Guess I'll have to come up with something different or make my own somehow. Good try, though...