What is the best metal for a knife?

[mkwarren]

I know there is not a blanket answer for this question, but here is what I have learned, maybe that will help you know what i'm looking for.

I am looking to make a few knives out of the hardest metal I can find. I have seen a few blades out of M2, but no manufacturers. Looking at some data about M steels, it seems M4 is the highest end as far as hardness (63 in the case of M4) without sacrificing toughness and becoming brittle. Sure higher M steels such as M42 can get much much harder, but it seems anything above M4 just gets brittle. M4 seems to be able to go to 63 rhc before getting brittle

I know that D2 is the most popular steel for higher end knives. Its very hard and is basically stainless. But what about the higher end D steels. I know some people use D6.

And then there is CPM Rex 121. So far in my research it seems this is the "ultimate". In fact if you google CPM Rex 121 you see almost nothing but knives. And the Crucible data shows it can get to 70.5 hardness without sacrificing toughness. Thats crazy hard. But i'm told it cannot be bought in flatstock, which means I have to either pay someone to forge it, or buy a furnace and anvil (i did see a guy get metal red hot with a torch and a few firebricks).

What would you conciser to be the "ultimate" steel for building a super hard super slicing knife?

Side question, what grind should i use with these super hard metals. will a plain V grind be sufficient or is it necessary to do a convex edge?

Thanks for the info and advice.

 

[A.McPherson]

While I know next to nothing about the specific steels you are talking about, I do know that unless you have LOTS of cash to drop on equipment, the chances of making a good knife out of those "super steels" is pretty minimal. Especially for a beginner. Read the stickies and lots of your questions will be answered.

 

[Stacy E. Apelt - Bladesmith]

Many answers depending on your finances and circumstances.

Cowry - X
ZDP-189
CPM-M4
Hitachi white paper

 

[mkwarren]

While I know next to nothing about the specific steels you are talking about, I do know that unless you have LOTS of cash to drop on equipment, the chances of making a good knife out of those "super steels" is pretty minimal. Especially for a beginner. Read the stickies and lots of your questions will be answered.

Since i'm buying a piece of flatstock and paying another guy to temper it, the cost wont be too bad. I can use a hacksaw or angle grinder to shape the metal and a rotery tool with sanding bits to fine tune the shape.

itl cost me about 42-44 bucks to have it tempered.

 

[AddictedToGear]

For a strong knife and very sharp I look at Rocksteads. But of course their grind that they so is what makes them so good. They have an excellent heat treat and grind. They use a few different steels. I would check out their website. M4 is very good and is used in production knives, but I am not a steel expert however I do think their are better steels to be used. Heat treat and grind have a large effect on the RC and the durability.

 

[mkwarren]

yea. i'v dreweld over some of the rockstead knives. i just do not have 4 grand for a knife. lol

I've thought about doing the convex grind they use. its not hard really. you just use sandpaper rather than stones. You loose sharpness due to the edge being thicker, but you gain lots of strength, due to the edge being thicker.

It may be necessary for these types of steel to do a convex grind, i don't really know. a question i'm waiting for an answer on.

 

[mkwarren]

ZDP-189 looks pretty dang good. 2 hardness points above m4. maybe i should have went with that.

 

[Fanglekai]

Rockwell hardness rating is only a small factor. The microstructure and geometry are what matter.

 

[Rhinoknives1]

Since i'm buying a piece of flatstock and paying another guy to temper it, the cost wont be too bad. I can use a hacksaw or angle grinder to shape the metal and a rotery tool with sanding bits to fine tune the shape.

itl cost me about 42-44 bucks to have it tempered.

It sounds like you have no or very little steel shaping experience?

I suggest you make one out of a less expensive common but excellent steel first.
1084 or CPM-154 with the latter being my choice. The geometry of your blade for your given slicing chore is very important as well, and of course the Heat treat being done properly.

For a slicing culinary knife. If thats what you are reffering to? I feel a full flat grind or a slightly convexed blade work best.

 

[Fanglekai]

You need a good belt grinder to shape these steels.

Also you need precise and expensive equipment to heat treat most of these steels. They aren't simple carbon. The heat treatment schedule is extremely unforgiving for most high alloy steels.

 

[mkwarren]

It sounds like you have no or very little steel shaping experience?

you got it!

i've already ordered the M4. now, being that D,M and REX steels are high speed tool steels made to cut metal, would they not be ideal for knives? (maybe not M and Rex as they have no corrosion resistance)

 

[mkwarren]

You need a good belt grinder to shape these steels.

Also you need precise and expensive equipment to heat treat most of these steels. They aren't simple carbon. The heat treatment schedule is extremely unforgiving for most high alloy steels.

Paying another knife guy to do the heat treatment.

I have a desk top grinder. ill be honest, i'm worried about how its gonna turn out.

If i make a 2nd one (probably out of zdp 189 or rex 121) i might sell it, if thats the case i can sell it for the cost of the materials, treating and a cheap belt grinder.

i'm sure harbor freight has one for about 40 bucks

 

[Fanglekai]

you got it!

i've already ordered the M4. now, being that D,M and REX steels are high speed tool steels made to cut metal, would they not be ideal for knives? (maybe not M and Rex as they have no corrosion resistance)

High wear resistance isn't necessarily the best trait for a pocket knife. Edge stability, ease of sharpening, corrosion resistance, toughness, strength.....there are many important traits to balance.

 

[Fanglekai]

Paying another knife guy to do the heat treatment.

I have a desk top grinder. ill be honest, i'm worried about how its gonna turn out.

If i make a 2nd one (probably out of zdp 189 or rex 121) i might sell it, if thats the case i can sell it for the cost of the materials, treating and a cheap belt grinder.

i'm sure harbor freight has one for about 40 bucks

Is he an experienced heat treater? Is his equipment precise enough? Does he know the heat treat schedule and how to avoid embrittlement zones? Does he know which temper cycle to use?

These are not simple steels. Rex121 is insane to work. Look at Farid's thread. He went through a ton of belts to shape knives from Rex121.

 

[zcd]

Is he an experienced heat treater? Is his equipment precise enough? Does he know the heat treat schedule and how to avoid embrittlement zones? Does he know which temper cycle to use?

These are not simple steels. Rex121 is insane to work. Look at Farid's thread. He went through a ton of belts to shape knives from Rex121.

These are extremely valid points. The best blade steel *for you* at this point in time is without a doubt 1084

 

[i4Marc]

What is your experience level?
How many knives have you made?
Do you know the proper thermal cycling, annealing and normalizing procedures for the steels you are considering?
Do these steels require cryo?
If you are not doing the HT, does the person who will have experience heat treating such exotic steels?
Who will be the end user (yourself, a friend or family member, a sportsman, a soldier, a chef)?
In what environment or under what conditions will they be using the knife (temps, moisture or water, salt, chemicals, dirt, urban or remote)?
What will the blade be expected to handle (food chores, hardwood chopping, skinning animals, prying open car doors, puncturing 55 Gal drums or body armor)?
What kind of edge do you want (glassy smooth or toothy)?
Will the blade need to be resharpened in the field?

A lot of thought and information goes into designing, making and heat treating a knife. These questions and many others should be considered. Just scrutinizing a steel chart to see which one gets the hardest does not necessarily point to the best steel for a given application. The different percentages of alloys can give very different performance characteristics between steels of similar hardness. Maybe if you tell us more about who you are making the knife for and how they'll be using it you will get more specific advice.

 

[mkwarren]

He is experienced with M steels. I have not asked about rex steels. I do know that they will do the M in a vacuum. which i read is necessary.

I know that m4/rex 121 are not necessarily "idea" for a knife. i guess my goal is to kind of push the limits on the edge and see how far i can get with it as far as sharpness and retention.

if this hobby becomes successfull. I might make 2 different types. rex121 for gear heads and zdp for everyone else.

 

[mkwarren]

What is your experience level?
How many knives have you made?
Do you know the proper thermal cycling, annealing and normalizing procedures for the steels you are considering?
Do these steels require cryo?
If you are not doing the HT, does the person who will have experience heat treating such exotic steels?
Who will be the end user (yourself, a friend or family member, a sportsman, a soldier, a chef)?
In what environment or under what conditions will they be using the knife (temps, moisture or water, salt, chemicals, dirt, urban or remote)?
What will the blade be expected to handle (food chores, hardwood chopping, skinning animals, prying open car doors, puncturing 55 Gal drums or body armor)?
What kind of edge do you want (glassy smooth or toothy)?
Will the blade need to be resharpened in the field?

A lot of thought and information goes into designing, making and heat treating a knife. These questions and many others should be considered. Just scrutinizing a steel chart to see which one gets the hardest does not necessarily point to the best steel for a given application. The different percentages of alloys can give very different performance characteristics between steels of similar hardness. Maybe if you tell us more about who you are making the knife for and how they'll be using it you will get more specific advice.

At the moment. It's just for me. I would like to push the envelope sota speak on sharpness and retention.

as far as day to day use. obviously with m4 ill have to stay out of the water. and obviously field sharpening isnt realistic. tho. the idea is to not have to sharpen it till you get back from the field. that statement could mean a lot of different things, some of which an exotic alloy would not be preferable.

experience level - 0
how many have i made - 0
what is cryo?
the guy doing the heat treating has experience
family/friends and sportsmen would be the ideal people using this type of steel knife.
Would be kind of cool to see if a rex 121 blade can cut a steel drum and still be sharp. i think ill make that my goal.

 

[Fanglekai]

He is experienced with M steels. I have not asked about rex steels. I do know that they will do the M in a vacuum. which i read is necessary.

I know that m4/rex 121 are not necessarily "idea" for a knife. i guess my goal is to kind of push the limits on the edge and see how far i can get with it as far as sharpness and retention.

if this hobby becomes successfull. I might make 2 different types. rex121 for gear heads and zdp for everyone else.

For pure sharpness a low alloy steel like Hitachi white, blue, super blue, AEB-L or simple carbon steels like 1095 are ideal. They will take and hold highly polished edges and remain stable even at low angles, assuming proper HT.

Edge retention isn't wear resistance. Wear resistance isn't edge retention. If you want to retain a low sharpness edge then consider high wear resistance steels.

There are steels specifically designed for cutlery. Some steels have a set of material properties that works well for small or large knives for a set of specific tasks. There is no one perfect steel for everything.

Do you have the skill and gear to sharpen high wear resistance steels?

 

[12345678910]

In my opinion, you are moving to farr, to fast - biting off more than you can chew.


You are looking at very expensive materials that will be very difficult to work.


Start soft, small, and cheap.

Start with a small simple knife, start with a simple annealed steel that will be easy to work.

Try 1084

If it is done properly, you will be pleased compared to commercial knives.


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