magnacut toughness in a long fixed blade.

[Nathan the Machinist]

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.

View attachment 1762149

Idunno man. I've worked with 4V V4E quite a bit on my path to developing the heat treat and knives that have won the majority of the cutting competitions in the last several years and I have seen a lot of its failure modes but you have a pretty cool chart there and a very strong argument so I expect you probably could make a good sword from 4V. While I probably wouldn't (personally) I think it could be pretty cool and you should try it. I have made some pretty cool competition swords from optimized 3V and it seems like a pretty good material for the application so you might consider that too.

When I say chippy mushy I mean chipping (small areas are missing with limited yielding in the area of the failure) and mushy (denting and edge roll leading to burrs and flat spots without missing bits) which is a very common problem with a lot of knives and "super steels" that have super fantastic cut results in soft abrasive media like rope and card stock but sometimes suck in real life where the edge turns into an accidentally serrated mess when used like a normal person to strip insulation, pry a staple or accidently clack the side of a beer bottle when opening a case of beer. Assuming you drink beer. In bottles. Folks are so used to this they think it's normal.

I tend to agree with you that it is often a problem with the heat treat, but it is very very common and is pretty typical in many, if not most, knives made in certain materials like the high chrome stainless super steels and other complex high alloy steels. 4V is a good example of a material that shows this issue with reduced edge stability when given the heat treat on the data sheet (intended for tool and die) and this is a great example of a material that heat treaters (not just me) have utilized processes very different than the data sheet to achieve the results we want in the thin sections of a knife edge. These tweaks tend to avoid the secondary hardening hump and put a focus on the conversion of retained austenite in the quench rather than after temper to minimize less cohesive mixed structures (RA and the various things it can decompose into) and carbon lean martensite that may work fine in a stamping tool but can play hell in the sections of a knife edge in normal use.

One can have two knives of the same material, same geometry and same rockwell hardness that have very different edge retention properties depending on the heat treat. A knife given a heat treat that works great in tool and die may have a comparatively chippy mushy edge when compared to a knife given a heat treat designed for knives. This is actually pretty common.

I have started using the term "durable" in reference to a knife edge that holds up in rough use. People often say "wow, that's really tough" when in reality it is often anything but tough. A tough alloy and heat treat are often pretty mushy (stabilized retained austenite can be tough) and show a lot of damage in rough use because they're soft (even if just in microscopic areas like the perforations in a postage stamp). Soft is tough, but soft is not durable. We're usually going for a durable edge because (issues with wear resistance aside) durability is the key to good edge retention. It's not a metallurgically correct term but it's a helpful term for the actual property we're discussing because "tough" is often used wrong here and "edge stability" can get you strange looks.

 

[Rockwelledge75]

Idunno man. I've worked with 4V V4E quite a bit on my path to developing the heat treat and knives that have won the majority of the cutting competitions in the last several years and I have seen a lot of its failure modes but you have a pretty cool chart there and a very strong argument so I expect you probably could make a good sword from 4V. While I probably wouldn't (personally) I think it could be pretty cool and you should try it. I have made some pretty cool competition swords from optimized 3V and it seems like a pretty good material for the application so you might consider that too.

When I say chippy mushy I mean chipping (small areas are missing with limited yielding in the area of the failure) and mushy (denting and edge roll leading to burrs and flat spots without missing bits) which is a very common problem with a lot of knives and "super steels" that have super fantastic cut results in soft abrasive media like rope and card stock but sometimes suck in real life where the edge turns into an accidentally serrated mess when used like a normal person to strip insulation, pry a staple or accidently clack the side of a beer bottle when opening a case of beer. Assuming you drink beer. In bottles. Folks are so used to this they think it's normal.

I tend to agree with you that it is often a problem with the heat treat, but it is very very common and is pretty typical in many, if not most, knives made in certain materials like the high chrome stainless super steels and other complex high alloy steels. 4V is a good example of a material that shows this issue with reduced edge stability when given the heat treat on the data sheet (intended for tool and die) and this is a great example of a material that heat treaters (not just me) have utilized processes very different than the data sheet to achieve the results we want in the thin sections of a knife edge. These tweaks tend to avoid the secondary hardening hump and put a focus on the conversion of retained austenite in the quench rather than after temper to minimize less cohesive mixed structures (RA and the various things it can decompose into) and carbon lean martensite that may work fine in a stamping tool but can play hell in the sections of a knife edge in normal use.

One can have two knives of the same material, same geometry and same rockwell hardness that have very different edge retention properties depending on the heat treat. A knife given a heat treat that works great in tool and die may have a comparatively chippy mushy edge when compared to a knife given a heat treat designed for knives. This is actually pretty common.

I have started using the term "durable" in reference to a knife edge that holds up in rough use. People often say "wow, that's really tough" when in reality it is often anything but tough. A tough alloy and heat treat are often pretty mushy (stabilized retained austenite can be tough) and show a lot of damage in rough use because they're soft (even if just in microscopic areas like the perforations in a postage stamp). Soft is tough, but soft is not durable. We're usually going for a durable edge because (issues with wear resistance aside) durability is the key to good edge retention. It's not a metallurgically correct term but it's a helpful term for the actual property we're discussing because "tough" is often used wrong here and "edge stability" can get you strange looks.

I agree with most of your points but an expertly heat treated 4v blade should be plenty durable in your terms, and by durable I hope you also include in your definition non brittle, because if your edge is brittle it doesn't matter how hard it is it's going to fail just as bad if not worse than a mushy edge only with lots of chipping. so, therefore durable in the case of chopping blades needs to be understood as this perfect balance of toughness and hardness in a particular steel and not just the hardness factor on the hrc scale alone.

Edit: on a side note, I'm not saying a full length sword on the order of a katana or something should be attempted in 4v but these camp swords/ some what longer thinner chopper like blades and certain types of bolos would probably be fine. If someone were to attempt a full length sword in 4v/ cruwear/ magnacut ect I'd expect it'd have to be heat treated below hrc 59, which while would be perfectly functional it may not give the desired qualities of resistance to rolling the edge as some better steel suited for the application would give but then again who knows, maybe if you made the spine thick enough on a 25 inch or so blade you might be ok with a slightly higher rockwell number, I don't know anyone making full length or close to full length swords out of steels in this particular toughness class though.

 

[shinyedges]

I agree with most of your points but an expertly heat treated 4v blade should be plenty durable in your terms, and by durable I hope you also include in your definition non brittle, because if your edge is brittle it doesn't matter how hard it is it's going to fail just as bad if not worse than a mushy edge only with lots of chipping. so, therefore durable in the case of chopping blades needs to be understood as this perfect balance of toughness and hardness in a particular steel and not just the hardness factor on the hrc scale alone.

Have you destruction tested 4v in longer blades? I'm curious what your experience is.

 

[Rockwelledge75]

Have you destruction tested 4v in longer blades? I'm curious what your experience is.

I have not but I've used a friend's custom machete in cpm cruwear to cut through multiple oak branches in a day's work with no damage and he's used it on mostly pine for years. I am currently having a roughly 20inch long (16inch long blade) machete style chopper made in cpm magnacut, once it's finished I'll report back after I put it through a full 7 days worth of work chopping oak and let you know how it goes.

 

[nattynarwhal]

I agree with most of your points but an expertly heat treated 4v blade should be plenty durable in your terms, and by durable I hope you also include in your definition non brittle, because if your edge is brittle it doesn't matter how hard it is it's going to fail just as bad if not worse than a mushy edge only with lots of chipping. so, therefore durable in the case of chopping blades needs to be understood as this perfect balance of toughness and hardness in a particular steel and not just the hardness factor on the hrc scale alone.

Edit: on a side note, I'm not saying a full length sword on the order of a katana or something should be attempted in 4v but these camp swords/ some what longer thinner chopper like blades and certain types of bolos would probably be fine. If someone were to attempt a full length sword in 4v/ cruwear/ magnacut ect I'd expect it'd have to be heat treated below hrc 59, which while would be perfectly functional it may not give the desired qualities of resistance to rolling the edge as some better steel suited for the application would give but then again who knows, maybe if you made the spine thick enough on a 25 inch or so blade you might be ok with a slightly higher rockwell number, I don't know anyone making full length or close to full length swords out of steels in this particular toughness class though.

If treating to 59 hrc is the target, why not use z-tuff or 3v? At that rockwell, both has the same edge stability as 4v and are much much tougher. 4v and cruwear really shine once you up the hardness

 

[Rockwelledge75]

If treating to 59 hrc is the target, why not use z-tuff or 3v? At that rockwell, both has the same edge stability as 4v and are much much tougher. 4v and cruwear really shine once you up the hardness

You could but 3v toughness is a little over kill for a chopper I think, at hrc 59 or heck even at hrc 61 3v has proven to be tough enough for full length swords, the blade I'm going for I need it capable of reaching hrc 63 to 64 while being stainless and hopefully tough enough to handle the work I'm doing, it'll be really interesting to see how it pans out once it's done.

 

[Mecha]

I have started using the term "durable" in reference to a knife edge that holds up in rough use.

I've been using "resilient," a nod to the modulus of resilience metric.

I have not but I've used a friend's custom machete in cpm cruwear to cut through multiple oak branches in a day's work with no damage and he's used it on mostly pine for years. I am currently having a roughly 20inch long (16inch long blade) machete style chopper made in cpm magnacut, once it's finished I'll report back after I put it through a full 7 days worth of work chopping oak and let you know how it goes.

I bet it's going to perform admirably.

 

[Rockwelledge75]

I've been using "resilient," a nod to the modulus of resilience metric.




I bet it's going to perform admirably.

Thanks, I have high hopes for it!

 

[patrickguignot]

I am currently having a roughly 20inch long (16inch long blade) machete style chopper made in cpm magnacut

Very curious to know who is doing this machete for you. I'm interested

 

[dtcls100]

I agree with most of your points but an expertly heat treated 4v blade should be plenty durable in your terms, and by durable I hope you also include in your definition non brittle, because if your edge is brittle it doesn't matter how hard it is it's going to fail just as bad if not worse than a mushy edge only with lots of chipping. so, therefore durable in the case of chopping blades needs to be understood as this perfect balance of toughness and hardness in a particular steel and not just the hardness factor on the hrc scale alone.

Edit: on a side note, I'm not saying a full length sword on the order of a katana or something should be attempted in 4v but these camp swords/ some what longer thinner chopper like blades and certain types of bolos would probably be fine. If someone were to attempt a full length sword in 4v/ cruwear/ magnacut ect I'd expect it'd have to be heat treated below hrc 59, which while would be perfectly functional it may not give the desired qualities of resistance to rolling the edge as some better steel suited for the application would give but then again who knows, maybe if you made the spine thick enough on a 25 inch or so blade you might be ok with a slightly higher rockwell number, I don't know anyone making full length or close to full length swords out of steels in this particular toughness class though.

Dawson knives is making katana style swords in 3v and Magnacut at HRC 60-61. Bought a 23 inch blade in 3v. Fantastic quality and tough. There is a video on their website of a 3v sword blade being bent 30 degrees each way. After tension removed, it is still perfectly straight! Dawson makes some of the very best fixed blades sold. I have three and am planning on a fourth. Only real problem with Dawson is that they are frequently sold out!

 

[dtcls100]

Dawson knives is making katana style swords in 3v and Magnacut at HRC 60-61. Bought a 23 inch blade in 3v. Fantastic quality and tough. There is a video on their website of a 3v sword blade being bent 30 degrees each way. After tension removed, it is still perfectly straight! Dawson makes some of the very best fixed blades sold. I have three and am planning on a fourth. Only real problem with Dawson is that they are frequently sold out!

Actually a 3v knife blade bent to almost 45 degrees one way and about 30 degreesthe other way. Video is on Youtube under 3v flex torture test.

 

[shqxk]

I do believe when it comes to very long fixed blade or sword, simple alloy steel like 5160 or 8670 is a much better choice over most PM tool steel because most of the time the edge will dull from deformation/chipping and all we need is a high toughness steel with reasonable hardness that sharpen easily... High wear resistance wouldn't be very usefull for this aside from add on the difficult in sharpening.

 

[jstn]

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’s word on steel is always good enough for me. Thanks for the input, sir!

 

[jstn]

Dawson knives is making katana style swords in 3v and Magnacut at HRC 60-61. Bought a 23 inch blade in 3v. Fantastic quality and tough. There is a video on their website of a 3v sword blade being bent 30 degrees each way. After tension removed, it is still perfectly straight! Dawson makes some of the very best fixed blades sold. I have three and am planning on a fourth. Only real problem with Dawson is that they are frequently sold out!

I would t want a katana in MagnaCut. I do have a Dawson Big Bear in MagnaCut that’s held up well to chopping and batoning

 

[dtcls100]

I do believe when it comes to very long fixed blade or sword, simple alloy steel like 5160 or 8670 is a much better choice over most PM tool steel because most of the time the edge will dull from deformation/chipping and all we need is a high toughness steel with reasonable hardness that sharpen easily... High wear resistance wouldn't be very usefull for this aside from add on the difficult in sharpening.

That may be true for alot of PM tool steels, but certainly not CPM 3V and possibly Magnacut (which many consider as falling within the stainless category in terms of properties, but not chromium content). With proper heat treatment, 3V is as tough as (or tougher than) 5160, with far superior edge retention and much better corrosion resistance. So while 5160 can be used to make excellent long blades, there really is no advantage to using 5160 over CPM 3V, other than 5160 is cheaper. Magnacut, while not quite as tough as CPM 3V, is still quite tough and has even better edge retention than CPM 3V and extremely high corrosion resistance that is only exceeded by steels like Vanax and H1. Indeed, Spyderco is starting to use Magnacut for their Salt series. Dawson Knives tests all of their products carefully before putting them up for sale. Consistent with this, Dawson was initially somewhat slow to use Magnacut for longer blades, but gradually have been increasing the length of their blades using Magnacut. With katana type swords, they first introduced Magnacut in 17 inch blades, then after a while in 20 inch blades, now they are up to 23 inch blades. Still haven't introduced Magnacut in their 25 inch blades, but we will see. BTW, Dawson uses Ceracote on their CPM 3V blades to reduce chance of corrosion.

 

[shqxk]

That may be true for alot of PM tool steels, but certainly not CPM 3V and possibly Magnacut (which many consider as falling within the stainless category in terms of properties, but not chromium content). With proper heat treatment, 3V is as tough as (or tougher than) 5160, with far superior edge retention and much better corrosion resistance. So while 5160 can be used to make excellent long blades, there really is no advantage to using 5160 over CPM 3V, other than 5160 is cheaper. Magnacut, while not quite as tough as CPM 3V, is still quite tough and has even better edge retention than CPM 3V and extremely high corrosion resistance that is only exceeded by steels like Vanax and H1. Indeed, Spyderco is starting to use Magnacut for their Salt series. Dawson Knives tests all of their products carefully before putting them up for sale. Consistent with this, Dawson was initially somewhat slow to use Magnacut for longer blades, but gradually have been increasing the length of their blades using Magnacut. With katana type swords, they first introduced Magnacut in 17 inch blades, then after a while in 20 inch blades, now they are up to 23 inch blades. Still haven't introduced Magnacut in their 25 inch blades, but we will see. BTW, Dawson uses Ceracote on their CPM 3V blades to reduce chance of corrosion.

According to knifesteelnerds toughness testing, 5160 is about 12.5% tougher than CPM-3V at 59.5HRC. 5160 will be much easier to sharpen due to the lacks of Vanadium carbide. User can sharpen 5160 on natural or simple stone while it would required some complex stone or ceramic for CPM-3V.


More importantly, in a long knife/sword, the shape, geometry and overall balance can be more importance than steel performance. Sometime a significant distal tapering is required. So steel like 5160 or 8670 which can be forged to shape or ground off without wasting so much $$$

 

[dtcls100]

While the charts do show 5160 as having slightly higher toughness than 3v at 59.5 hrc, different heat treatments can make a difference. Moreover, the differential hardening that Dawson swords are given, with a hardened edge but softer shock absorbing spine, further accentuates their toughness. In any event, any toughness differences at such a high level of toughness for both steels is really insignificant as opposed to such a percentage difference between low toughness steels. While very tough, 5160 has extremely low corrosion resistance (not affected by geometry) and very low edge retention, while 3v is actually pretty good in both categories and far superior to 5160. CPM-3v has small vanadium carbides so it is not difficult to sharpen. 5160 may be easier to sharpen, at the cost of having to sharpen much more frequently, which is significant when dealing with a long blade as opposed to a 3 inch kniife. You do not want to sharpen a sword on a rock! The balance of qualities heavily favors 3v over 5160 with 5160’s only real advantage being cost. However, the cost of the steel in a sword is typically a minor factor.

 

[dtcls100]

While the charts do show 5160 as having slightly higher toughness than 3v at 59.5 hrc, different heat treatments can make a difference. Moreover, the differential hardening that Dawson swords are given, with a hardened edge but softer shock absorbing spine, further accentuates their toughness. In any event, any toughness differences at such a high level of toughness for both steels is really insignificant as opposed to such a percentage difference between low toughness steels. While very tough, 5160 has extremely low corrosion resistance (not affected by geometry) and very low edge retention, while 3v is actually pretty good in both categories and far superior to 5160. CPM-3v has small vanadium carbides so it is not difficult to sharpen. 5160 may be easier to sharpen, at the cost of having to sharpen much more frequently, which is significant when dealing with a long blade as opposed to a 3 inch kniife. You do not want to sharpen a sword on a rock! The balance of qualities heavily favors 3v over 5160 with 5160’s only real advantage being cost. However, the cost of the steel in a sword is typically a minor factor.

Also, while I agree that a sword’s balance and design can be more important than the steel used, a sword need not be forged to have a proper balance. This is a function of proper design. It is quite clear that can computer/laser cut PM bar stock into virtually any shape and more readily obtain more complex tapers with more consistency than forging. My Dawson sword has a complex taper and pretty much perfect balance as confirmed by photos and multiple reviews. I can balance the sword on my front index finger notch.

 

[fullswing]

I have not but I've used a friend's custom machete in cpm cruwear to cut through multiple oak branches in a day's work with no damage and he's used it on mostly pine for years. I am currently having a roughly 20inch long (16inch long blade) machete style chopper made in cpm magnacut, once it's finished I'll report back after I put it through a full 7 days worth of work chopping oak and let you know how it goes.

I'd love to revive this thread, did the machete in Magnacut ever get tested? Thanks to all contributors of this thread btw, tons of useful information for a sword enthusiast interested in super steels.

 

[Chronovore]

Paging David Mary . He has experience with this.