BM Mini-Ritter(M390) chipped and rolled after piercing through tire (pictures)

S

Saint 3:16

Joined
Mar 1, 2015
Messages
66
Definitely not the knife's/steel's fault, should have researched what tires are made of first lol.

Full story: Ritter is a current edc, definitely hard use it. In fact, the m390 has probably done more than 300 cuts of cardboard and some wood whittling prior today, and could still cut phone book paper. Anyways, there's a street in my neighborhood where people always dump their garbage and there's always a couple used tires along there. I wanted to see how "easily" my knife could puncture a tire so I just had to try it out. Went pretty easily through the side wall, and then attempted to cut through. A few passes after, I noticed the damage.

Had to reprofile it a couple degrees higher to get the chipping out. Mirror polish put on.

Lesson learned, until next time.

https://goo.gl/photos/NazG4rLTLBRWj6rLA

https://goo.gl/photos/y3cjdiDr6xHAkiXr9

https://goo.gl/photos/1SW1AyJcHABvwQje7
 
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I pierced through the top of the side wall and did a few passes/cuts diagonally towards the bottom, but stopped after just a few passes, no where near the steel belt
 
There is sometimes a steel bead that runs around the tire where it mounts to the rim.
Did you hit that by chance?
 
No, no where near the tire mounts. Blade degree was around 19-20 degrees per side. Pierced very easily and just slight rolling at the top of the blade, most of the damage at the belly when I did the cuts
 
Yep agreed u most definitely hit the wire inside the tire, that sucks! Hate that for ya.
 
Do you have a jewelers loupe? Can you see if the chips come out of the same side?

This would be a sign of a lateral load exceeding the edge stability.
Due to the alloy being a CPM and stainless, it isn't going to have the raw toughness that a fine grained carbon steel will exhibit. If this were done with a comparable blade of 52100, or even AEB-L for a stainless option, I doubt the chipping would have been as severe, if occurring at all.

I take the m390/cts-204p/20cv materials as being a high carbide slow wearing alloy when it comes to abrasive wear (cardboard, insulation, et al) and not a straightforward "tougher" alloy.

I would sharpen up your knife and possibly give it another shot and see if the factory edge was beat up a bit by the powered sharpeners at the factory (a common issue amongst many brands).
Then retouch the edge again, and use it as a wear resistant alloy, not one to test toughness and lateral fine edge stability.
 
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NJBillK said:
I would sharpen up your knife and possibly give it another shit and see if the factory edge....
Click to expand...

I hate it when that happens...but funny...
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The damage to your blade is interesting...as generally a soft blade will "roll," whereas the harder steels may "chip."
And you managed to get both.
BTW, I love my M390 blades...but they don't see hard use.
 
Lol, for the longest time, I was autocorrecting my phone to actually curse.
Now it just goes about on its own and is set on causing me to gain an infraction...
 
most newer tires also use kevlar in the sidewall construction for strength and kevlar is some badass schitt(think bullet proof vest)
 
Saint 3:16 said:
Definitely not the knife's/steel's fault, should have researched what tires are made of first lol.

Full story: Ritter is a current edc, definitely hard use it. In fact, the m390 has probably done more than 300 cuts of cardboard and some wood whittling prior today, and could still cut phone book paper. Anyways, there's a street in my neighborhood where people always dump their garbage and there's always a couple used tires along there. I wanted to see how "easily" my knife could puncture a tire so I just had to try it out. Went pretty easily through the side wall, and then attempted to cut through. A few passes after, I noticed the damage.

Had to reprofile it a couple degrees higher to get the chipping out. Mirror polish put on.

Lesson learned, until next time.
Click to expand...

Had to point this out. Though I can't say much, as I also like to "test" the abilities of my knives too but also because I tried to use M4 to cut through a steel can. It struggled but made it. Definitely not worth it though.
 
For cutting steel cords, I prefer a high carbide non stainless. They take the least damage I've experienced.
 
This would be a sign of a lateral load exceeding the edge stability.
Due to the alloy being a CPM and stainless, it isn't going to have the raw toughness that a fine grained carbon steel will exhibit. If this were done with a comparable blade of 52100, or even AEB-L for a stainless option, I doubt the chipping would have been as severe, if occurring at all.

I take the m390/cts-204p/20cv materials as being a high carbide slow wearing alloy when it comes to abrasive wear (cardboard, insulation, et al) and not a straightforward "tougher" alloy.
Click to expand...

NJBillK, an excellent and easy to understand explanation. Many don't take the lateral loads into consideration and think just because a steel is tough it shouldn't be damaged as no chopping or batoning was even done. Thin edges can be susceptible even on tough steels with decent edge stability depending on the geometry and lateral forces involved. Even the toughest steel knives don't do well as screwdrivers. Thanks!

Joe
 
A high carbide non stainless? Like 3v and it's family, M4, D2. 10v/A11 are a very high carbide non stainless steels but I'd expect chipping from them. Never cut tires so I don't know.
 
d00mtr33 said:
A high carbide non stainless? Like 3v and it's family, M4, D2. 10v/A11 are a very high carbide non stainless steels but I'd expect chipping from them. Never cut tires so I don't know.
Click to expand...
I shoulda been more specific, high speed steels - m2, m3, m4, m35, m42, t42, hap40, etc.
A11/10v/k390 types are ok but end up a little more damaged. D2 or any stainless, forget it, they get completely trashed.

I regularly cut a lot of small steel cable with a knife when prepping high voltage armored wiring, coax, and shielded cable. Also cut through sheet metal, cut into nuts & bolts unwiring motors, ream stainless tubing, scrape unknown substances from glass sight tubes and metal ID tags, scribe lines in metal, scrape corroded electrical connections.... If you want to know how stable an edge is (rolling/chipping), try some of the above tasks with your knives.
 
Jpm, you should do yourself s favor and get in touch with two guys, Luong LA (Bluntcut Metalworks) Gary Creely (GSCreely). They have both been doing some exciting worth with setting what they can get out of alloys or using less common ones.

From Luong I have a 52100@64rc, W2@64hrc and a 10v@68hrc. All of them are Fantastic performers.

From Gary I have a CPM Rex 76 B&T@64hrc tempered down from 67-68, so it still has some impressive toughness. I think he still has a couple blanks laying around too.
Rex 76 is basically a slightly more alloyed HAP40.
Take a look here.
 
Howdy Bill, I do have a few BCMW blades in 52100, w2, and zwear, one being to my specs (a true custom). They are excellent when it comes to edge stability, slightly better than my hss ones. But 2 things, they are fixed blades, which are inconvenient at work, and they dull quicker than hss. I do use them a lot around the house and at least two always goes with us out of town on trips.

What I really want is a folder to my specs, with BCMW CWF hss blade.
I'm watching closely Luongs progress with cpm m4.

In the meantime, I'm waiting for a maxamet native 5.
 
He has done some re heat treats of blades before.
I suggest you shoot him an M4 blade from a Gayle Bradley or Manix sprint to be part of his testing. And you be on the receiving end of it afterwards. Especially if you can send him two blades to compare them then you sell the stock one.

Maxamet has caught my eye, the mule in particular, due to the hardness. I think they were a bit harder than the manix and others offered.
 
I happen to have a couple of Gayle Bradleys, one NIB, and would be willing to send them to Luong for testing.
What I really want is something similar to a Spyderco Sage 1 with CWF cpm m4 1/2 to 2/3 high saber ground blade and .4" hole.... *dreaming*
 
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