CPM REX 45 vs CPM M4 torture test

That is VERY interesting. One reason I sold my pm2 in rex 45 was becasue I liked M4 better.

While REX is certainly harder,
I personally think M4 is "tougher" as in resistant to chipping.
M4 had mostly rolled and REX had no rolls at all and when the threshold was reached it only chipped.

IF M4 was at the same HRC as REX, I wonder if it would be harder than the brass with the same resistance to chip?

Nice to know it has a higher Wear resistance than Hap40
All this and still pleasant to sharpen.


Dang...I now regret selling my PM2:(

To late to Pre-order a Millie?:rolleyes:
 
We still have some important variables in the HAP-40 vs. REX 45 test.

Edge geometry:
1. Total included angle of each apex. His hand held sharpening stones wobble quite a bit and results in the apex in convex shape. This is not necessarily a poor apex,, in fact I prefer the convex shape however, we do not know if each knife had identical apex geometry.
2. Thickness of blade immediately behind the apex.
3. Total included angle of main blade, the Endure is considerably thinner stock wrt the PM2. Does this result in less support for the apex and affect results?

I appreciate the time and effort expended in the video but it was lacking in some areas.

Regards,
FK
 
Both M4 and REX 45 are tool steel.
Tool steel by definition is developed to cut metal.
Metal that is soft, not heat treated steel, as well as non ferrous brass.
Think of the tool bit in a lathe,,, years ago before we had so much inexpensive carbide, tool bits were made of HSS (high speed steel) which was very similar to M4. Today we have cutters for milling machines, drill bits, etc. made of M4 steel.

Not a big deal to shave brass,,, it is abuse to gouge out chunks with a twisting motion as Shawn did in his video. Good demo of toughness on the brass rods.

Regards,
FK
 
Always a pleasant surprise finding out a steel can do something it wasn't supposed to.
I for one doubted this steel from the get go, figuring it was nothing more than American Hap40, now completely dumbfounded by how a higher HRC can completely change a steels properties.
 
  • Like
Reactions: mb>
TRfromMT said:
Do mere mortals with a basic sharpmaker stand a chance at sharpening Rex 45?
Click to expand...

I think it will sharpen well on the Sharpmaker. Vanadium content is what has frustrated me in the past using ceramic rods. Rex 45 has less Vanadium than S30V. One of the sharpening guru's here made a comment that's stuck with me. He said S30V and above in V content (4%), and he's using diamond abrasive. Rex 45 has about 3% V.

It's very similar in makeup to Hap40, which was the first steel I was able to get a hair-whittling edge off the brown rods. It sharpens very well. Hopefully the higher hardness doesn't affect that too much.
 
Not that I'm cutting brass, but I'm finding rex-45 very responsive to stropping. Even a garbage strop. lol.

zGMnMCd.jpg
 
bearfacedkiller said:
The price we pay for knowledge. ;) There is too little real info out there on PSF27 so I sent it his way. I trust him. There might be a regrind in it for me too. :) It was a little too thick for my tastes so I look forward to getting it back better than new.

It was reprofiled to about 30 degrees so the edge angle should be about the same. I can say that it took it well. He will be sharing it at some point.
Click to expand...
Can’t wait to see the results! I had my local knifemaker put a new edge on my Bradley Bowie and it is a lot better now. I’m anxious to see the possible regrind!
 
Murphjd25 said:
Can’t wait to see the results! I had my local knifemaker put a new edge on my Bradley Bowie and it is a lot better now. I’m anxious to see the possible regrind!
Click to expand...

Yeah, mine came with extremely obtuse bevels, especially towards the tip. Was quite a chore to get it all rebeveled, especially with such an upswept tip, but it made a huge difference.

I am anxious to get it back too but I don’t really need it back right away either. I have more knives than I have things to cut. :) I just hope he is having fun with it and that the community gains something. There is almost zero info on that knife or PSF27.
 
I have 4 pm2s and only one Millie. I need to preorder the Millie in this steel.
(Not that I can find a PM2 but haven’t hunted much for one. I have never had 4 of one model either, not there’s anything wrong with that :))
 
Last edited:
sharp_edge said:
For those of you who do not have time to watch Michael Christy's test video, here is the most important things I got:

Hap40 Endura and Rex 45 PM2 were sharpened to the same sharpness of whittling hair before the test. He cut cardboard with the same portion of the blade and alternating between two knives. He stopped when the knife no longer shaved hair.

Hap40 Endura: 924 inches cut
Rex 45 PM2: 1122 inches cut.
Click to expand...
I love Rex 45
 
I have some unscientific calculations here. 3" of CPM-M4 straight from the factory, on the Sage 5, will do light everyday cutting cut for five months to the day. I gave my girlfriend her Sage on Valentines Day, and today (She works Sun-Thurs so this is like her Saturday, yesterday was last work day and was the 14th, so...5mo to the day) she told me that I should touch up her Sage. She said it snagged cutting bubble wrap. She is used to really sharp good knives now, because I got her used to them. I tested the knife on newspaper just now, and it still slices through the paper no problem. It's just the tip and the inch or so toward the end of the blade, that is a little rougher.

The knife is still totally able to cut and work with, it has just lost that "razor sharpness", it doesn't catch my nail for the inch at the tip of the blade. Any "normal" person using M-Techs and gas station stuff for years and years would absolutely still say this is a crazy sharp knife. I just shaved some leg hair with it! Awesome. So, I could only imagine how much this knife could take before it is truly DULL.

Giving her my BD1N aluminum PM2 to use while I do my first touch-up of CPM-M4. Very impressed with the stuff.
 
JBoone said:
I have 4 pm2s and only one Millie. I need to preorder the Millie in this steel.
(Not that I can find a PM2 but haven’t hunted much for one. I have never had 4 of one model either, not there’s anything wrong with that :))
Click to expand...
Only four? I have eight, those are rookie numbers, gotta pump those numbers up 😂
Kidding. I also never thought I would own multiples of a knife like this, and I also have only one Military. The whole reason I got on the PM2 train is because there were no base model Millies when I first went to get a Spyderco, so I got a PM2, and it's history from there...
 
You must log in or register to reply here.
Back
Top