To M4 or not to M4...

[sok]

If I saw a knife that I wanted that had a REX45 blade, it wouldn't be a negative since it compares favorably to CPM M4. I am full up on M4 though, so my knife steel interests are about expanding my experience, not a lateral move. For example, I am not interested in the REX45 steel in the PM2, but very interested in the K390.

Would REX45 get the DLC love that the M4 gets?

[Albatross]

This has made me wonder about body chemistry as well. Does one steel react differently than the other? I have no idea. My Rex blade barely has a patina, while my M4 began to rust, and you have experienced the opposite. I'm curious now.

Here's a pic of my fairly well worn Mantra taken a few moments ago, just to prove I'm not completely nuts. (The stuff in the Spyderhole was some lint.)

It's almost impossible to get the patina to show up in a picture.

I'll see about getting a picture of my Rex45 Military on here later. Your knife looks very rust-free and on my phone, the patina isn't noticeable.

[Albatross]

I know everyone is going nuts over rex45 because it ran 67 hrc - but what's stopping m4 from being run that high? Do the components that allow it to be a hot work steel allow it to achieve a higher hardness?

The cobalt in Rex45 is what allows the steel to be hardened to 67 hrc. M4 can't reach the same hardness, which means it falls behind in edge retention. As Larrin said, at the same hardness(both at 64 for example), the steels have similar edge retention.

[A.S.O.K.A]

I dont think that rex45 should replace m4 because both steels have one up over each other. Rex45 has better edge retention than m4, and m4 has better impact resistance than rex45. So all in all, its a matter of what the user is really looking for in the trade off. Do you want a knife that you can accidently run over a staple while cutting cardboard and suffer minimal damage? Or do you want a knife that can cut more cardboard?

[Deadboxhero]

I dont think that rex45 should replace m4 because both steels have one up over each other. Rex45 has better edge retention than m4, and m4 has better impact resistance than rex45. So all in all, its a matter of what the user is really looking for in the trade off. Do you want a knife that you can accidently run over a staple while cutting cardboard and suffer minimal damage? Or do you want a knife that can cut more cardboard?

The Rex 45 is acutually more durable of an edge. Impact toughness is more about shock resistance, like swinging the knife like an axe or hammering on the spine like a cold chisel.

The M4 is mostly more shock resistant because it is softer HRC and the heat treated and tempered microstructure has more gummy patches of retained Austinite.

But that doesn't translate to more durablity with Staples, that feature lowers the strength and stability of the edge and it gets chowdered when misused like that.

I feel people need to experience more Cruwear , 4v , Rex 45 , K390 , and 10v. People don't know what they haven't really gotten a chance to play with, they might feel that these other materials offer more performance than M4, but M4 is what people know and what's available for people to buy in production knives. Companies haven't fully committed to pumping out more knives in these steels yet.

Spyderco has been leading the charge.

[A.S.O.K.A]

I feel people need to experience more Cruwear , 4v , Rex 45 , K390 , and 10v. People don't know what they haven't really gotten a chance to play with, they might feel that these other materials offer more performance than M4, but M4 is what people know and what's available for people to buy in production knives. Companies haven't fully committed to pumping out more knives in these steels yet.

Spyderco has been leading the charge.

I definitely agree. I'm always happy when trying a new steel. The latest one I've tried is cruwear. Definitely hope for K390 in a model I want to carry. The other models in k390 to date have not tickled my fancy. But yes, hopeful to try the steel as well as others. And hope to see a collab with you and spyderco some day too

[GarageBoy]

Is 4v, rex45, k390 significantly harder to sharpen than m4? I'm guessing diamond stones are a necessity. Does maxamet work as an alternative to the above mentioned steels - more accessible without chasing Sprint runs

I've only touched up m4, and am more used to simple steels.

[Deadboxhero]

Is 4v, rex45, k390 significantly harder to sharpen than m4? I'm guessing diamond stones are a necessity. Does maxamet work as an alternative to the above mentioned steels - more accessible without chasing Sprint runs

I've only touched up m4, and am more used to simple steels.

Nah, none of those are necessarily more difficult to sharpen compared to M4. Diamond/CBN is best practice for all of these kinds of steels including M4.
Technique is king.

K390 will take longer to reprofile. However, K390 makes up for it with how well it apexs and deburrs over M4.

[Albatross]

This has made me wonder about body chemistry as well. Does one steel react differently than the other? I have no idea. My Rex blade barely has a patina, while my M4 began to rust, and you have experienced the opposite. I'm curious now.

Here's a pic of my fairly well worn Mantra taken a few moments ago, just to prove I'm not completely nuts. (The stuff in the Spyderhole was some lint.)

It's almost impossible to get the patina to show up in a picture.

The patina only shows at certain angles, but this is from several months of use, without oiling the blade or using rust protection. The colors you see are actually the reflection of my tv. The actual patina is just grayish/black.



I'm thinking it may have been the finish on my PM2, but I don't really know. As long as I have a steel that performs similarly and doesn't rust from opening the knife, I'm happy.

[Robishere]

I find M4 ti be the dram cutter with astounding edge retention, but the cpm-20cv is growing on me. I got severely spoiled with a Gayle Bradley2 with the weight, smoothness, stunning machining, and solid feel. After that I wanted another Spyderco in that quality but Alas, just plastic handles with thin weak liners (the para anything) and I gave away all but my maxamet para whatevers. The maxamet is a dream to use and actually re sharpens very easily much like the m4.
I ended up buying 2 Zero Tolerance knives, both the 0562. One was full titanium and the other is titanium and carbon fibre.
The 20cv is harder to sharpen than the m4 to me, but holds an edge well. T is hard to say if it is a favourite since the blade is so **** thick it is like trying to slice cardboard with a hatchet.
The M4 and Maxamet blow any other steels out of the water for cutting and are easy to sharpen....right until the Canadian winters of sleet and snow and slush with salt splashing....and your m4 gets wet and you cannot carry it! GAAA! So then I have my ZT knives on 20cv.
I tried s110v and after trying to re sharpen them a few times threw the blades in the garbage and kept the handles for parts. I found it over priced and a fad that I sadly was part of. Why not make a solid cobalt or solid tungsten blade and call it s5000v that no human can sharpen? The maxamet beat s110v’s *** all around town and sharpened almost as easily as vg10.
A stainless rival to m4 would be nice ONLY IF it is as easy to sharpen as m4.
I have not tried rex45 yet, but if it is anything like s110v I will keep my cpm-20cv for winter and rain and my maxamet and m4 for nice weather.

[Albatross]

I find M4 ti be the dram cutter with astounding edge retention, but the cpm-20cv is growing on me. I got severely spoiled with a Gayle Bradley2 with the weight, smoothness, stunning machining, and solid feel. After that I wanted another Spyderco in that quality but Alas, just plastic handles with thin weak liners (the para anything) and I gave away all but my maxamet para whatevers. The maxamet is a dream to use and actually re sharpens very easily much like the m4.
I ended up buying 2 Zero Tolerance knives, both the 0562. One was full titanium and the other is titanium and carbon fibre.
The 20cv is harder to sharpen than the m4 to me, but holds an edge well. T is hard to say if it is a favourite since the blade is so **** thick it is like trying to slice cardboard with a hatchet.
The M4 and Maxamet blow any other steels out of the water for cutting and are easy to sharpen....right until the Canadian winters of sleet and snow and slush with salt splashing....and your m4 gets wet and you cannot carry it! GAAA! So then I have my ZT knives on 20cv.
I tried s110v and after trying to re sharpen them a few times threw the blades in the garbage and kept the handles for parts. I found it over priced and a fad that I sadly was part of. Why not make a solid cobalt or solid tungsten blade and call it s5000v that no human can sharpen? The maxamet beat s110v’s *** all around town and sharpened almost as easily as vg10.
A stainless rival to m4 would be nice ONLY IF it is as easy to sharpen as m4.
I have not tried rex45 yet, but if it is anything like s110v I will keep my cpm-20cv for winter and rain and my maxamet and m4 for nice weather.

Rex45 has better edge retention than M4, and many people have also found it easier to sharpen. Toughness is lower, but edge stability is higher, so unless you're going to pry or chop with it, Rex45 wont disappoint.

[Robishere]

I think I will have to get some to experiment with it! To me M4 is the dream steel, but it is a headache when it is a blizzard or raining etc.
I have been let down so many times by anything stainless as far as edge holding or re sharpening.
Aus 6 aus 8 vg10, etc.... they can take a scary edgr for a few swipes whittling wood or cut a few plastic binder tied and t is time to re sharpen, or s110v that chips a lot and then takes 2 hours to get sort of sharp. Sure you can leave them in snow (who does that?) they just are not that gifted at being sharp or cutting.
I agree that I have pry bars, so toughness is bot a big thing (for me). If the rex45 will behave like the M4 I would give it a shot.

[Woodpuppy]

I’ve been very content with M4. I like cruwear quite well too. I have not rotated my rex45 into use yet; probably should. I’m finally getting a nice patina on my bhq para 3, and I’m not ready to “move on” from M4! I’d be delighted for them to coexist though!