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Has Anyone Ever Made Knives from These Materials?

My background is in the aerospace industry where I worked for 35 years. I can't help but think of three metals that conceivably could be used in knife fabrication. For the blades, has anyone made them out of 300M heat treated to 280,000 psi? It is an expensive steel that has terrific strength but also has good ductility. It is used a lot in the places of the plane that have high stresses and a small space to put it into. Usually steels heat treated to 280,000 psi are brittle, and would not be a good choice. One problem with 300M would be corrosion, so the blade might need to be plated. I think the advantage would be an edge that would keep its sharpness a very long time.

The cadillac of aerospace steels is called MP35N. You can heat treat it to about the same level as 300M and is also ductile. But it's real advantage is it is a stainless steel. This stuff is amazing, but very costly. It has cobalt in it, thus raising the price. But you wouldn't have to face about corrosion issue. Again this would hold an edge very well.

Lastly I can't help but think of magnesium for other parts of the knife. Magnesium has the highest strength to weight ratio than just about any other metals including aluminum. This stuff is amazing also. You pick it up and it feels like a feather, and yet it has impressive strength characteristics. It could be used to make a super lightweight knife. Two problems would exsist however. One would be corrosion; it corrodes fairly easily. The other would be ignition/burning. If the metal was hot and a spark contacted it, it might ignite. And if it does it is nasty; very hot fire. The only way to put out a magnesium fire is to simply let it burn itself out. But I think it would work as long as it stayed away from the campfire. I know of a certain bomber that has a major brake component made out of magnesium, and it has been used successfully for more than 50 years. It is banned from commercial aircraft because of the burning issue.

I wrote these "out of the box" ideas just because I thought you might find it interesting. Feel free to comment and/or call me an idiot.

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In MemoriamPermalink Reply by D ale on October 11, 2012 at 21:07

I know the same steel used for ball bearings in the aerospace industry has been successfully used for cutlery steel .. will have to look up the specifics though .. haven't read or referenced that article in yrs.

As an engineer w/ 20+ yrs in the steel fab industry .. I am unfamiliar w/ pounds per square inch (psi) being used relative to heat treatment. Is that, by chance, the pressure at which shear occurs .. or .. failure in some other manner ?? I am familiar w/ materials being tested to the point of failure and the result being a psi rating ..but.. not for heat treatment. Please clarify.

I'll take a look @ some old reference material & see what's available relative to the exact specs on that "aerospace ball bearing" steel I read about. Will post when I find.

D ale.

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In MemoriamPermalink Reply by D ale on October 11, 2012 at 22:28

There's a general reference for cutlery steels HERE.

I find neither 300M or MP35N listed. However, 300M's cousin, AISA 4340 is listed.

MP35N is the tradename of Special Metals Group of Companies and equivalent to:

• UNS R30035

• AWS 110

... both of which I find no listing for in the earlier quoted "cutlery steel general reference". Reviewing MP35N's specs .. it might possibly find an application as a "diver's knife" .. but I'm not aware of it's general use as such.

......................................................... just a WAG .. cost prohibitive ????

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Permalink Reply by Alexander Noot on October 12, 2012 at 0:36

I'm sorry....but using Magnesium for a handle is just ASKING for trouble. Too great of a risk. And not enough gain.

The other two I don't know about. Corrosion should'nt be much of a problem. Plenty of makers that make carbon steel and Tool steel knives non coated and they do just fine. Usually they take a bit of a patina and are well protected from the elements after that.

Can you tell us a little bit more about the steels you mention? Composition? Heat treatment? Attainable rockwell hardness? I'm affraid I'm no engineer and I don't know much about PSI on materials. But I'm a knifemaker and I know hRC and steel composition.

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Permalink Reply by Jan Carter on October 12, 2012 at 5:49

wow, this is an awesome discussion and I am going to have to do some searching to see if there is anything out there made of these. I am certainly going to learn a bit about different metals. Thanks guys

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Permalink Reply by Stanley May on October 12, 2012 at 7:43

Attached is a word document with a table that converts ultimate tensile strength (UTS) to various hardness levels. In my discussion the stress levels that I refer to are UTS. The UTS refers to the failure stress level. ie, a UTS of 280,000 psi means if you had a 1" x 1" bar (area = 1 in^2), you could pick up 280,000 lbs with it, but no more or it would fail.

Attachments:

Rockwell.doc, 104 KB

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Permalink Reply by Stanley May on October 12, 2012 at 8:10

The stress levels I am refering to is Ultimate Tensile Strength. So the failure mode is tensile stress (not shear). Heat treatment has a direct impact on the UTS. The same steel can be heat treated differently to obtain the desired UTS. In a real general sense, the higher the heat treat (hardness) the more brittle the material becomes.

D ale said:

I know the same steel used for ball bearings in the aerospace industry has been successfully used for cutlery steel .. will have to look up the specifics though .. haven't read or referenced that article in yrs.

As an engineer w/ 20+ yrs in the steel fab industry .. I am unfamiliar w/ pounds per square inch (psi) being used relative to heat treatment. Is that, by chance, the pressure at which shear occurs .. or .. failure in some other manner ?? I am familiar w/ materials being tested to the point of failure and the result being a psi rating ..but.. not for heat treatment. Please clarify.

I'll take a look @ some old reference material & see what's available relative to the exact specs on that "aerospace ball bearing" steel I read about. Will post when I find.

D ale.

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Permalink Reply by Alexander Noot on October 12, 2012 at 8:19

Am I reading that thing right in that 280.000 PSI is around Rockwell 30-35 on the C scale? If so then the stuff is completely unusable as a knife steel. way way WAY too soft.

As for Cobalt in steel. It's nothing new really. Just kind of expensive. Check out knifemaker David Boye. He makes knives with Cobalt steel. Calls is Dendentric (I think) steel. Very corrosion resistant and still takes a nice edge.

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Permalink Reply by Stanley May on October 12, 2012 at 8:54

You are looking at the wrong scale for UTS. It is the 7th column over. Rock C is the first column

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Permalink Reply by Stanley May on October 12, 2012 at 9:12

Everyone, my discussion was "out of the box". I just suggested these materials to spark your intellect, and perhaps get you thinking of out of the box ideas as well. I enjoy out of the box ideas. My mentioning them does not mean that I would recommend them. Some serious studies would have to be performed to really make it a bonified material. I have some strong reservations myself about them. The purpose was more "for fun" than seriousness, although there is some logic in considering these materials.

In the end, sometimes out of the box ideas generate other ideas that are good ideas. I guess I should have mentioned these ideas are not totally recommended by myself.

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Permalink Reply by Stanley May on October 12, 2012 at 19:22

You are right, mp35n would be hard to sharpen. It would take diamond tools that is for sure. But once it was sharpened, it would stay sharpened for a long time.

I am not suggesting making the blade out of magnesium, otherwise it definitely could ignite in the process. When the piston housing of this bomber made from mag. is machined, machining oil continually sprayed on it. But even if you made the blade of steel and the rest from mag., you might accidentally touch a grinding wheel or whatever on the mag. and that could be a problem. You would probably want to detach the blade when sharpening it. It was a wild idea.

I have not worked with machines that make knives, so I am not a machining expert. My role was to calculate the stresses and other people were responsible for materials and machining.

Ron"TUNA"Dumeah said:

Stanley, I would love to see some of these get to production. Have you ever worked with machines to make knives. If so I would love to see your work. As an Engineer I am sure you could find away to do some of these things.....One question about the cobalt edge. Is it so durable that it would be hard to sharpen it? Bring the next question, if you built a knife out of magnesium could it catch fire in the sharping or re sharping process?

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Permalink Reply by Alexander Noot on October 13, 2012 at 0:22

You're right, my bad. I did see the Rockwell C scale column. But I looked in the wrong column for the other variable. Look like the steel would attain around rockwell 58-60 which is really nothing special. And you said it was kind of brittle at that hardness?

Stanley May said:

You are looking at the wrong scale for UTS. It is the 7th column over. Rock C is the first column

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Permalink Reply by Stanley May on October 13, 2012 at 8:54

I said in a very general sense, when steels (like 4330 and 4340) are heat treated, to higher and higher UTS levels they become more brittle. 300M and MP35N are special steels that maintains good ductility at a UTS of 280,000 psi. I believe 300M is actually 4330: however it is processed in a vacuum. That way the steel cannot absorb hydrogen and cause hydrogen embrittlement which makes the steel brittle.