thin edges and high HRC steels : another aspect of durability

[Cliff Stamp]

If you read pretty much even a few of Alvin's posts on rec.knives you will notice the focus on obtaining maximum strength in knives when heat treating steels. For a lot of discussions on durability the viewpoint tends to be one of impact toughness and ductility which is fairly relevant for large knives when chopping, however for cutting strength can be more important.

I have been using one of Alvin's 1095 full hard 1095 blades, 66 HRC, 1/16" steel, full hollow grind, ~5 degree edge, paring knife pattern, as an EDC for awhile now basically trying to see what you can and can't do with it. I can cut any manner of soft materials (ropes, cardboards, foods), however it also carves hardwoods such birch flooring. It can also carve bone and whittle on various metals, however cutting them such as opening a can requires a more robust edge, I have more work to do to see just how much.

As a comparison, weaker steels can be less durable even though possibly tougher in regards to impacts. For example I took the 1095 paring knife and cut right into the center of the end of a 2L pop bottle with no problems. However a small Sebenza ground to a similar profile suffered edge warping without even being able to come close to making the same cuts. The edge was visibly damaged, in the sections used to cut the plastic the edge just rippled unable to take the strain and tore/cracked.

-Cliff

 

[aldo]

I was just wondering what HRC to run some cpm-m4.
what is your opinion?
as long as I'm asking have you had any experience with cpm-154cm cpm-3v or cpm-m4 and if so what did you think about the steels in general?

p.s. I just got a zdp calypso and at 64-65 it seems to take the finest edge of any knife I have. I hand sharpened it on a DMT fine/ultra fine stone then stroped it on a rig I got from busse at the blade show. not sure what angle. I used 3 dimes as a guide. it is a little more shallow and a little more sharp than the NIB edge.

THANKS!
ALEX

 

[Cliff Stamp]

I was just wondering what HRC to run some cpm-m4 ...

It gets up to 66 HRC, that is where I would start the R&D. I would like to see some statistics on its tensile strength, wear resistance and grain size in regards to the soak temp / tempering temperature.

as long as I'm asking have you had any experience with cpm-154cm cpm-3v or cpm-m4 and if so what did you think about the steels in general?

CPM-154 is fairly new, it is essentially goaled to have better machinability than S30V, I don't find this to be a problem so I have little interest in it.

CPM-3V looks very good on paper, however in practice on a couple of knives it wasn't impressed. I'd still like to try a custom from Phil Wilson in it at its peak toughness.

I have not used CPM-M4, there are several high REX steels which would be interested as well, they get up to 72 HRC.

[calypso jr]

...it seems to take the finest edge of any knife I have.

Very hard steels in general tend to take very high levels of sharpness do to minimal burr formation, the fine grain of the CPM process increases this further.

-Cliff

 

[aldo]

At what HRC was the 3v you tested?

On paper cpm-m4 looks better to me 62hrc 32 toughness 20-25 wear resistance
3V at 62, 40, 7

m4 same hrc, same toughness, better wear resistance

what do you think?

I wonder what kind of toughness m4 would have at 66hrc?

THANKS
ALEX

 

[Cliff Stamp]

At what HRC was the 3v you tested?

60 HRC. I had problems with hardening though, I have seen this with a tip which bent way too easily (SchottD. The Ferhman had better strength but chipped too easily.

I wonder what kind of toughness m4 would have at 66hrc?

In regards to bending or impact, really low. However it should never be used for knives that are going to be loaded in such a manner. These steels are best suited for very thin knives with deep hollow grinds and very acute edges, blades which are opimized as pure cutters.

-Cliff

 

[the possum]

Just to side track a bit,

CPM-3V looks very good on paper, however in practice on a couple of knives it wasn't impressed. I'd still like to try a custom from Phil Wilson in it at its peak toughness. ...I have seen this with a tip which bent way too easily (Schott D). The Ferhman had better strength but chipped too easily.

I too have been impressed with 3V's numbers on paper, but have never gotten to try any out. I was thinking about using it on a great big chopper that will probably meet hard materials.

I don't want the edge to chip or ripple, nor do I want the blade to bend or break. Impossible to get everything, I know, but the numbers suggest 3V should still perform better in real world use than even L6. Are you with holding your opinion until you've done more testing?

 

[Cliff Stamp]

Are you with holding your opinion until you've done more testing?

Pretty much, I have not wrote off on it just not impressed with what I have seen. I still have loosely planned a large knife in 3V at ~58 HRC by Wilson, I'd also like a bainite L6 / 5160 knife.

-Cliff