magnacut toughness in a long fixed blade.

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Rockwelledge75

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For those that have experience with Magnacut, CPM cruwear and or cpm4v, since they are all around the same toughness, in a long blade of say 12 to 16 inches is a thickness of .156 sufficient for a robust enough spine or bevel to give it enough toughness or resilience against shock when cutting into hardwood?
 
Well, 4v is used in competition choppers for the type of work you're talking about, and magnacut mirrors it's toughness up until around 63 HRC. So I'd imagine you'll be okay unless you really push hardness beyond the 64+ mark.
 
I would say definitely "maybe". My experience with Cruwear shows it not to like lateral stresses on a thin edge at all. So if you can guarantee your cutting/chopping force is exactly perpendicular to whatever you are cutting, you should be fine. "Maybe." :p

I personally would not be completely comfortable with Cruwear with a .15" spine unless my edge geometry was at least 23-24 DPS. And that may be too obtuse for your requirements. And as Natty said above, HRC plays a big role as well.
 
nattynarwhal said:
Well, 4v is used in competition choppers for the type of work you're talking about, and magnacut mirrors it's toughness up until around 63 HRC. So I'd imagine you'll be okay unless you really push hardness beyond the 64+ mark.
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That's a very good point, thank you. How thick are those choppers usually?
 
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shane45-1911 said:
I would say definitely "maybe". My experience with Cruwear shows it not to like lateral stresses on a thin edge at all. So if you can guarantee your cutting/chopping force is exactly perpendicular to whatever you are cutting, you should be fine. "Maybe." :p

I personally would not be completely comfortable with Cruwear with a .15" spine unless my edge geometry was at least 23-24 DPS. And that may be too obtuse for your requirements. And as Natty said above, HRC plays a big role as well.
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and that's cpm cruwear we are talking you have experience with right? would a convex edge help at all you think?
 
shane45-1911 said:
Typically .25", but I have seen quite a few even thicker at .375" (3/8").
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I don't know much about blade competition but at a demonstration I watched the few choppers I looked at from close range had spines around 3/8". They had fairly tall blades so the angles weren't very steep.
 
Rockwelledge75 said:
Dang at .375 that's one big mass of metal right there you could probably rockwell up to 65 and be just fine lol.
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Magnacut sees a pretty steep toughness drop after 63 hrc. But then again, competition choppers have been made in M4 which is less tough than both magnacut and 4v. I love magnacut at 65 though... sharpens well and deburrs like a dream. I have two magnacut fixies at 62.5 and 63 which sharpen super easy but the burr can be a pain to knock off.
 
nattynarwhal said:
Magnacut sees a pretty steep toughness drop after 63 hrc. But then again, competition choppers have been made in M4 which is less tough than both magnacut and 4v. I love magnacut at 65 though... sharpens well and deburrs like a dream. I have two magnacut fixies at 62.5 and 63 which sharpen super easy but the burr can be a pain to knock off.
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Yea the way I figure is if cpmM4 can handle the impact that choppers go through at HRC 63 to 64 when at a thickness of .25 to .312 then Magnacut should definitely be able to handle the impact at HRC 65 at .375 thick and probably even at .3 or possibly even slightly less but certainly at .375. Heck at .375 I wouldn't be surprised if S30v could handle the impact choppers go through at HRC 62.5 and I know for damn sure s30v has less impact resistance at 62.5 than Magnacut has at 65.

I said it before and I'll say it again .375 is THICC :p
 
Competition choppers are thick at the spine to add weight because there is a 10" blade length limit, and it helps with chopping power. A longer blade would be more effective, but it's a knife cut, not a sword cut. But the primary grind angle is pretty narrow and they're thin at the edge. They're actually very good cutters.

Comp cutters are not thick like that for spine strength. A thinner blade wouldn't break. A thin grind might break (lost chunks) but that's little to do with stock thickness at the spine. It's thick at the spine for mass.

They're run hard because the higher hardness gives a higher yield strength which reduces risk of bent primary grinds. This higher strength allows us to use a shallow S grind where a softer steel might need to be thicker and convex.

This high hardness can lead to micro chipping at the edge from impacts with hard targets. A hard knot in the wood (or trash grown into the wood) or the aluminum rim of a soda can cut lengthwise can damage any edge. Edge stability in rough use is the driving attributes we're looking for in a steel and so far V4E and CPM 4V are king.

Magnacut is a fantastic steel but in my limited experience with it so far, I don't think you're going to see it replace 4V in upper level competitions. What it will do, however, is bring relatively high performance edge stability (and edge retention) to the folks who have been encumbered with shitty stainless options that have no idea how good steel can hold up in real use. People equate the abrasive wear resistance values they see in certain industry cut tests and think it equates to edge retention. Edges don't just go dull from abrasive wear, it's usually issues with chippy mushy edge and Magnacut doesn't appear to have this problem like other complex stainless steels. It isn't magical, but it is going to be eye opening for some folks who have some mainstream heat treat S30V knife and think they have good performance.
 
Nathan the Machinist said:
Competition choppers are thick at the spine to add weight because there is a 10" blade length limit, and it helps with chopping power. A longer blade would be more effective, but it's a knife cut, not a sword cut. But the primary grind angle is pretty narrow and they're thin at the edge. They're actually very good cutters.

Comp cutters are not thick like that for spine strength. A thinner blade wouldn't break. A thin grind might break (lost chunks) but that's little to do with stock thickness at the spine. It's thick at the spine for mass.

They're run hard because the higher hardness gives a higher yield strength which reduces risk of bent primary grinds. This higher strength allows us to use a shallow S grind where a softer steel might need to be thicker and convex.

This high hardness can lead to micro chipping at the edge from impacts with hard targets. A hard knot in the wood (or trash grown into the wood) or the aluminum rim of a soda can cut lengthwise can damage any edge. Edge stability in rough use is the driving attributes we're looking for in a steel and so far V4E and CPM 4V are king.

Magnacut is a fantastic steel but in my limited experience with it so far, I don't think you're going to see it replace 4V in upper level competitions. What it will do, however, is bring relatively high performance edge stability (and edge retention) to the folks who have been encumbered with shitty stainless options that have no idea how good steel can hold up in real use. People equate the abrasive wear resistance values they see in certain industry cut tests and think it equates to edge retention. Edges don't just go dull from abrasive wear, it's usually issues with chippy mushy edge and Magnacut doesn't appear to have this problem like other complex stainless steels. It isn't magical, but it is going to be eye opening for some folks who have some mainstream heat treat S30V knife and think they have good performance.
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Thanks for the insights, yea 4v is a workhorse for sure, it's really at this level of toughness we start to be able to see very interesting attributes emerge like being able to have an hrc of 62 to 63 and cut into aluminum or in some cases even semi thin nails with no chipping. since you say the spine doesn't really need to be anywhere near as thick as it is to take the impact I wonder how something more like a camp sword or bolo might fair in 4v.
 
4V is strong and durable but not especially tough (these words are sometimes used interchangeably but they have different meanings). It holds up pretty well in rough use but when it does break the failure mode is like dry spaghetti. I'm not sure I would use that in a sword.
 
Nathan the Machinist said:
it's usually issues with chippy mushy edge
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Nathan the Machinist said:
4V is strong and durable but not especially tough
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Can you explain what a chippy, mushy edge is, Nathan. My understanding is that chippy is low toughness and mushy is low strength. When you get both, something has gone wrong in the heat treat.

I also don't understand why you think Vanadis 4 Extra is not tough. What does "durable" mean in a knife steel. Larrin's data show that V4E is pretty darn tough. At 64.5 Rc, he doesn't list a tougher steel. At 58 Rc, V4E is tougher than O1.

And Larrin shows V4E as being tougher than CPM M4. They have about the same toughness when M4 is at 61.2 Rc and V4E is at 63.6 Rc.

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Twindog said:
Can you explain what a chippy, mushy edge is, Nathan. My understanding is that chippy is low toughness and mushy is low strength. When you get both, something has gone wrong in the heat treat.

I also don't understand why you think Vanadis 4 Extra is not tough. What does "durable" mean in a knife steel. Larrin's data show that V4E is pretty darn tough. At 64.5 Rc, he doesn't list a tougher steel. At 58 Rc, V4E is tougher than O1.

And Larrin shows V4E as being tougher than CPM M4. They have about the same toughness when M4 is at 61.2 Rc and V4E is at 63.6 Rc.

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I agree, I know there's some interplay with these words here but typically when I think of a "durable" knife I think of toughness and strength I think of as yield strength or resistance to bending or ability to spring back to true and while strength in this sense is usually linked with hardness this isn't always true 100% of the time, for instance there's unique steel microstructures that can be obtained with L6 and certain high silicon steels that create high yield strength at somewhat lower hardness than other steels but I digress, V4e/ cpm 4v is plenty tough, it's tougher than cpm M4 and cpm M4 has been shown to be plenty tough for camp swords' ie sword like blades below 16 inches, and even bolos with the correct edge geometry.
 
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