Why CPM 3V

[Mage7]

It really wouldn't be close. You'd see a jump with thinner geometry for sure, but the low carbide volume and relative hardness wouldn't compare to Maxamet and REX121. You need an adequate hardness to give the edge strength to support thinner geometry as well. Running 3V at 63-64 and thinning the edge out would push it closer to CruWear and 4V edge retention.

3V only has ~5% carbide volume while REX121 has ~30% and Maxamet has ~22%. No geometry is going to make enough of a difference to make up for that difference in carbide volume. I think this 3V would be cool if it's run at 63-64 in a folder. You get the toughness that 3V offers but the edge strength to give you much better edge retention. Save the softer stuff for fixed blades. I know it would be a tall task for Spyderco to hit that mark in a production setting, but if anyone could make it happen it's them.

It may seem hard to believe but the data show it to be true. For example, CPM-154 (not exactly a carbide monster) exceeded Maxamet simply by going from 15 dps to 10 dps. Geometry beats carbides.

That's just according to CATRA though. A box cutter blade that's too dull to bite into your finger tips will outcut an axe head that will shave your face in a CATRA test. Geometry dictates cutting ability, but sharpness doesn't necessarily dictate cutting ability.

[Brock O Lee]

The more I look at charts, the more I wonder why I wouldn't just go with LC200N...

Because LC200N is soft (high 50's) vs 3V (low 60's), and lacks the strength to not deform.

[Wartstein]

I wonder if this would actually pan out. As in if just 30% thinner/more acute geometry....

I say we get Sal to make us a C95 or a Bodacious in 3V and let's find out?

"Vivis" C95 in 3V and a 30 % thinner blade (if that is what you mean..?) should be an amazing folder...

[Synov]

That's just according to CATRA though. A box cutter blade that's too dull to bite into your finger tips will outcut an axe head that will shave your face in a CATRA test. Geometry dictates cutting ability, but sharpness doesn't necessarily dictate cutting ability.

But cutting ability is ultimately what we're talking about. You don't want to use an axe to cut cardboard regardless of how sharp it is. CATRA is the best proxy we have for determining edge retention in most common materials.

And I don't know why people would be worried about a thin 3V edge being unstable. There's a reason razor blades are not made from high carbide steels.

[tomhosangoutdoors]

It really wouldn't be close. You'd see a jump with thinner geometry for sure, but the low carbide volume and relative hardness wouldn't compare to Maxamet and REX121. You need an adequate hardness to give the edge strength to support thinner geometry as well. Running 3V at 63-64 and thinning the edge out would push it closer to CruWear and 4V edge retention.

3V only has ~5% carbide volume while REX121 has ~30% and Maxamet has ~22%. No geometry is going to make enough of a difference to make up for that difference in carbide volume. I think this 3V would be cool if it's run at 63-64 in a folder. You get the toughness that 3V offers but the edge strength to give you much better edge retention. Save the softer stuff for fixed blades. I know it would be a tall task for Spyderco to hit that mark in a production setting, but if anyone could make it happen it's them.

It may seem hard to believe but the data show it to be true. For example, CPM-154 (not exactly a carbide monster) exceeded Maxamet simply by going from 15 dps to 10 dps. Geometry beats carbides.

I agree 100%, but only in a lab setting like CATRA. 10DPS won't hold up for almost anyone in real world use. The tiniest amount of lateral pressure could be catastrophic. Higher carbide % = more wear resistance in normal use. Higher hardness = greater edge strength to support those thinner geometries without catastrophic failure.

[Mage7]

That's just according to CATRA though. A box cutter blade that's too dull to bite into your finger tips will outcut an axe head that will shave your face in a CATRA test. Geometry dictates cutting ability, but sharpness doesn't necessarily dictate cutting ability.

But cutting ability is ultimately what we're talking about. You don't want to use an axe to cut cardboard regardless of how sharp it is. CATRA is the best proxy we have for determining edge retention in most common materials.

And I don't know why people would be worried about a thin 3V edge being unstable. There's a reason razor blades are not made from high carbide steels.

Let's say you cut up a few dozen boxes or something one day, and you go home and decide to touch up the edge because it doesn't shave arm hair or cut printer paper easily.

Did you just test its cutting ability or its sharpness?

The answer depends on whether or not it was still cutting the material you dulled it on. If it could, it still had the ability to cut what you needed it to cut, right?

On the other hand if it couldn't shave or cut printer paper, you would be focusing on sharpness rather than cutting ability.

Or it may have still been able to cut the material you cut to dull it, and still shaved and cut printer paper, but you wanted to touch it up so that the forces required to cut the same material the next day were as low as possible for a little while. In that context, what's making the force to cut lower, the sharpness or the cutting ability?

CATRA doesn't test edge retention, it tests cutting ability, and not in a way that reflects how many users try to optimize it. I would say that most users who touch up a blade at the end of the day, or even concern themselves with how long a knife will remain shaving sharp or paper cutting sharp, are not as concerned about pure cutting ability as CATRA measures it.

Let's talk about real steels and use for a second. I have Mules in 15V, K294, and T15. According to CATRA, 15V should stay sharper for much longer than either K294 or T15, but in my actual experience T15 holds a shaving sharp edge longer than either 15V or K294. However all three of them cut over half a mile of cardboard during testing without any indication that they wouldn't cut 2-3x that amount before they actually lost their ability to cut it. Except I don't usually spend all day cutting cardboard, so I still wanted them to have an edge sharp enough to cut other material easily too even though I could still muscle them through cardboard.

...

As per your question about why people would be worried about it being unstable at thin geometries: Plastic deformation. Unless it was hardened to 65+ HRC then it will have a tendency to roll and dent more easily than high HRC steel, and especially at low edge geometry.

If you're asserting that razor blades don't roll or dent easily then I would encourage you to buy a few and use a laser goniometer to measure the edge angles and a pocket microscope to see the method of dulling. I'll save you the time and tell you that most are between around 24-34 degrees inclusive, and they dull from denting rather than chipping.

That may sound pretty acute but keep in mind that a straight razor would be 16-20 degrees inclusive. The reason DE razor blades are ground to a more obtuse angle is so they don't need to be hardened more to be able to resist plastic deformation, because then they'd suffer chipping more than denting. Chipping and fracturing tends to increase the edge apex radius a lot more rapidly than small dents do, which would more rapidly reduce their shaving ability.

3V would be great if it was left hard enough to perform the same way as razor blades, but lowering its angle would actually make it more prone to plastic deformation and require it to be harder to compensate. Then once it's harder it will lose its toughness advantage and be more prone to chipping and fracturing. I know that CATRA shows that thinner geometry means more cutting ability, but again that's not really a measure of sharpness as much as it is a measure of cutting ability. A very thin 3V blade will cut for a long time, but so would a moderately thin S110V blade. The S110V blade would dull by way of microchipping, but the 3V would dull by way of microdenting and neither one would be particularly sharp even though their cutting ability remained high.


Sorry for the long post, but I just really think people are misapplying the characteristics CATRA measures, especially in the context of edge geometry and sharpness.

[tomhosangoutdoors]

That's just according to CATRA though. A box cutter blade that's too dull to bite into your finger tips will outcut an axe head that will shave your face in a CATRA test. Geometry dictates cutting ability, but sharpness doesn't necessarily dictate cutting ability.

But cutting ability is ultimately what we're talking about. You don't want to use an axe to cut cardboard regardless of how sharp it is. CATRA is the best proxy we have for determining edge retention in most common materials.

And I don't know why people would be worried about a thin 3V edge being unstable. There's a reason razor blades are not made from high carbide steels.

I don't think 3V is inherently unstable. It just doesn't make much sense to run it softer (eg: 60-61) on a folder at this point. That's been done for years and the results are subpar. Fast edge blunting because it's too soft to have the edge strength to resist plastic deformation. It's a different animal at higher hardnesses and performs closer to 4V and CruWear while maintaining more toughness than either. It has a cool slot to fill in the lineup, but not at the hardnesses we've seen it at in production knives to this point.

[Synov]

I agree 100%, but only in a lab setting like CATRA. 10DPS won't hold up for almost anyone in real world use. The tiniest amount of lateral pressure could be catastrophic. Higher carbide % = more wear resistance in normal use. Higher hardness = greater edge strength to support those thinner geometries without catastrophic failure.

I know several people who use 10 dps without an issue. Even Sal does it. It all depends on what you're cutting.

Or it may have still been able to cut the material you cut to dull it, and still shaved and cut printer paper, but you wanted to touch it up so that the forces required to cut the same material the next day were as low as possible for a little while. In that context, what's making the force to cut lower, the sharpness or the cutting ability?

CATRA doesn't test edge retention, it tests cutting ability, and not in a way that reflects how many users try to optimize it. I would say that most users who touch up a blade at the end of the day, or even concern themselves with how long a knife will remain shaving sharp or paper cutting sharp, are not as concerned about pure cutting ability as CATRA measures it.

CATRA measures the amount cut from a specific amount of force, which also tells us how much force is needed to cut a specific amount. That is ultimately more important than when the knife can shave. The more obtuse the edge and the faster the knife dulls, the more force is needed.

I don't think 3V is inherently unstable. It just doesn't make much sense to run it softer (eg: 60-61) on a folder at this point. That's been done for years and the results are subpar. Fast edge blunting because it's too soft to have the edge strength to resist plastic deformation. It's a different animal at higher hardnesses and performs closer to 4V and CruWear while maintaining more toughness than either. It has a cool slot to fill in the lineup, but not at the hardnesses we've seen it at in production knives to this point.

I haven't seen it deform at 61 but I don't have a problem with it being at higher hardness either.

[vivi]

It really wouldn't be close. You'd see a jump with thinner geometry for sure, but the low carbide volume and relative hardness wouldn't compare to Maxamet and REX121. You need an adequate hardness to give the edge strength to support thinner geometry as well. Running 3V at 63-64 and thinning the edge out would push it closer to CruWear and 4V edge retention.

3V only has ~5% carbide volume while REX121 has ~30% and Maxamet has ~22%. No geometry is going to make enough of a difference to make up for that difference in carbide volume. I think this 3V would be cool if it's run at 63-64 in a folder. You get the toughness that 3V offers but the edge strength to give you much better edge retention. Save the softer stuff for fixed blades. I know it would be a tall task for Spyderco to hit that mark in a production setting, but if anyone could make it happen it's them.

It may seem hard to believe but the data show it to be true. For example, CPM-154 (not exactly a carbide monster) exceeded Maxamet simply by going from 15 dps to 10 dps. Geometry beats carbides.

I agree 100%, but only in a lab setting like CATRA. 10DPS won't hold up for almost anyone in real world use. The tiniest amount of lateral pressure could be catastrophic. Higher carbide % = more wear resistance in normal use. Higher hardness = greater edge strength to support those thinner geometries without catastrophic failure.

Have you tried a 10dps knife?

Me and Sal both carry them on a fairly regular basis without issue.

In my experience most people haven't taken edges thin enough to see how far they can go before things begin to fail with regular use. It may surprise you how thin you can get away with.

I see people on the kitchen mule thread fretting about 1.5-2mm stock being too thin for a chef knife, meanwhile one of my go to chef knives is 1mm stock.

IIRC Mora Companions have 11.5dps edges and I baton, carve wood and pry with those without issue as well.

[Mage7]

CATRA measures the amount cut from a specific amount of force, which also tells us how much force is needed to cut a specific amount. That is ultimately more important than when the knife can shave. The more obtuse the edge and the faster the knife dulls, the more force is needed.

CATRA uses a static force of 50 Newtons. That's about 12 lbs. How often do you bare down to cut something with 12 lbs of force?

Shaving was just an example of something that takes a low cut initiation force. Slicing paper is another standard test of it. Then you have things like slicing tomatoes, etc. At some point though you have to come up with your own approximation for the type of cutting you do, but when it comes to cut initiation force, the wider the edge apex radius the higher the cut initiation force, and the more acute the edge the more the edge apex radius increases after CATRA.

Don't just take my word for it...

https://knifesteelnerds.com/2018/08/06/ ... g-ability/

[Red Leader]

If we see a Mule Team in 3V, I wonder just what the HRC should be? I'm sure the factory will play w/ some different numbers, but what do you all think? 62? 63? I suppose maybe a MT may lend itself to a slightly different role (and therefore, hardness) than a folding knife. But, I do think a 3V Mule could be a great opportunity to play around with the heat treat to dial it in for future folding knife use.

Given its toughness, we have some headroom on the hardness to increase wear resistance, but of course the toughness factor is a big reason why we like it. Maybe there is a sweet spot.

[Red Leader]

Also, just gonna leave this here, but I'd still enjoy seeing a bit of a collab btw Carothers and Spyderco for a custom HT for 3V much in the same way we've seen BBB work with Spyderco on 15V...



Imagine this level of strength being utilitized in an ultra thin, super slicey folding blade.

[vivi]

CATRA measures the amount cut from a specific amount of force, which also tells us how much force is needed to cut a specific amount. That is ultimately more important than when the knife can shave. The more obtuse the edge and the faster the knife dulls, the more force is needed.

CATRA uses a static force of 50 Newtons. That's about 12 lbs. How often do you bare down to cut something with 12 lbs of force?

Shaving was just an example of something that takes a low cut initiation force. Slicing paper is another standard test of it. Then you have things like slicing tomatoes, etc. At some point though you have to come up with your own approximation for the type of cutting you do, but when it comes to cut initiation force, the wider the edge apex radius the higher the cut initiation force, and the more acute the edge the more the edge apex radius increases after CATRA.

Don't just take my word for it...

https://knifesteelnerds.com/2018/08/06/ ... g-ability/

Every day.

12lbs isn't a lot.

I just applied more force than that cutting through some double walled cardboard boxes. I regularly apply more than that with my thin japanese chef knives for certain tasks at work. I definitely applied more than that to my chopper doing trail maintenance last night before the storm hit.

[silver & black]

Also, just gonna leave this here, but I'd still enjoy seeing a bit of a collab btw Carothers and Spyderco for a custom HT for 3V much in the same way we've seen BBB work with Spyderco on 15V...



Imagine this level of strength being utilitized in an ultra thin, super slicey folding blade.

That's impressive.

[Synov]

CATRA uses a static force of 50 Newtons. That's about 12 lbs. How often do you bare down to cut something with 12 lbs of force?

I don't think it matters in order to show which blade requires more force to cut. The test result should be applicable beyond the criteria of the test, and I think this has been proven by correlation of CATRA results to other tests like rope-cutting.

Shaving was just an example of something that takes a low cut initiation force. Slicing paper is another standard test of it. Then you have things like slicing tomatoes, etc. At some point though you have to come up with your own approximation for the type of cutting you do, but when it comes to cut initiation force, the wider the edge apex radius the higher the cut initiation force, and the more acute the edge the more the edge apex radius increases after CATRA.

Don't just take my word for it...

https://knifesteelnerds.com/2018/08/06/ ... g-ability/

I understand, my point was that I don't really care about tasks that only require a sharp blade to initiate a cut, i.e. I don't really care about sharpness by itself. A sharp knife that takes more force to cut over time is worse than a dull knife that takes less force to cut over time.

[Synov]

If we see a Mule Team in 3V, I wonder just what the HRC should be? I'm sure the factory will play w/ some different numbers, but what do you all think? 62? 63? I suppose maybe a MT may lend itself to a slightly different role (and therefore, hardness) than a folding knife. But, I do think a 3V Mule could be a great opportunity to play around with the heat treat to dial it in for future folding knife use.

Given its toughness, we have some headroom on the hardness to increase wear resistance, but of course the toughness factor is a big reason why we like it. Maybe there is a sweet spot.

The toughness gives you so much room to play with, so I would like to see it in the higher end of the hardness range. And I would encourage Mule team testers to go to 10 dps to really see what it can do.

Also, just gonna leave this here, but I'd still enjoy seeing a bit of a collab btw Carothers and Spyderco for a custom HT for 3V much in the same way we've seen BBB work with Spyderco on 15V...



Imagine this level of strength being utilitized in an ultra thin, super slicey folding blade.

That would be awesome, although I'm not sure Nathan would want to share the details on his heat treat. Nathan is also developing an extreme hard use folder with a handle made of 3V with an integral pivot. So I don't think it would be anything like Spyderco makes, which may make him amenable to Spyderco producing a more mass-market slicey folder.

[Mage7]

CATRA measures the amount cut from a specific amount of force, which also tells us how much force is needed to cut a specific amount. That is ultimately more important than when the knife can shave. The more obtuse the edge and the faster the knife dulls, the more force is needed.

CATRA uses a static force of 50 Newtons. That's about 12 lbs. How often do you bare down to cut something with 12 lbs of force?

Shaving was just an example of something that takes a low cut initiation force. Slicing paper is another standard test of it. Then you have things like slicing tomatoes, etc. At some point though you have to come up with your own approximation for the type of cutting you do, but when it comes to cut initiation force, the wider the edge apex radius the higher the cut initiation force, and the more acute the edge the more the edge apex radius increases after CATRA.

Don't just take my word for it...

https://knifesteelnerds.com/2018/08/06/ ... g-ability/

Every day.

12lbs isn't a lot.

I just applied more force than that cutting through some double walled cardboard boxes. I regularly apply more than that with my thin japanese chef knives for certain tasks at work. I definitely applied more than that to my chopper doing trail maintenance last night before the storm hit.

Well, in that case, I think I know of the perfect knife for you. It's super tough steel too!

I don't think it matters in order to show which blade requires more force to cut. The test result should be applicable beyond the criteria of the test, and I think this has been proven by correlation of CATRA results to other tests like rope-cutting.

Like Cedric and Ada's rope cutting tests where he determines the stopping point by how well it still cuts paper? That's itself a measure of the cut-initiation force, and how much rope it's able to cut before it falls through a threshold of force able to cleanly cut paper, but again at any point the force being used to cut the rope might be quite high compared to the force someone might want to use to cut a piece of cardboard or a package or something right?

I understand, my point was that I don't really care about tasks that only require a sharp blade to initiate a cut, i.e. I don't really care about sharpness by itself. A sharp knife that takes more force to cut over time is worse than a dull knife that takes less force to cut over time.

The last sentence is kind of what in pointing out though. When we're talking about CATRA, we're already dealing with cutting forces that are high enough to drive a butter knife through a carrot. I dunno anyone that would call that sharp. Except maybe vivi but I'm still waiting to see how he'll respond

Now if I were gonna go put that butter knife in the video to a stone and put a super obtuse edge on it, let's say 40-45 degrees per side, but just make sure the apex was very crisp, do you think the force to cut would have been significantly lower, higher or unchanged? Obviously it would have been lower than the rounded edge on it now. Sharpness is still an integral part of cutting ability, even if cutting ability can still remain long after some threshold for sharpness has been exceeded.

What if instead I ground a really thin edge into it at 10 degrees per side, and then ground the apex flat? It would still cut the carrots with significantly less force, but how much less? Half? A quarter? If I could run my fingers up and down it without worry of being cut, but it still cut the carrot at 1/8th the cutting force would you consider that sharp? Because its cutting ability would be much higher as a thinner geometry would achieve in a CATRA test.

Anyway, this conversation seems to headed into circular territory. If your preference is truly to cut with really dull and thin knives then who am I to say that's wrong.

[vivi]

Well, in that case, I think I know of the perfect knife for you. It's super tough steel too!




The last sentence is kind of what in pointing out though. When we're talking about CATRA, we're already dealing with cutting forces that are high enough to drive a butter knife through a carrot. I dunno anyone that would call that sharp. Except maybe vivi but I'm still waiting to see how he'll respond

I don't understand the point you are trying to make. Could you clarify?

[Mage7]

Well, in that case, I think I know of the perfect knife for you. It's super tough steel too!




The last sentence is kind of what in pointing out though. When we're talking about CATRA, we're already dealing with cutting forces that are high enough to drive a butter knife through a carrot. I dunno anyone that would call that sharp. Except maybe vivi but I'm still waiting to see how he'll respond

I don't understand the point you are trying to make. Could you clarify?

That 12 lbs of cutting force is more than enough to cut a carrot with a butter knife.

I'm not sure what tasks you're doing that requires that much cutting force, particularly in the kitchen--and no, chopping doesn't count. If you were doing that all day, every day I couldn't imagine how sore you'd get. Imagine dicing carrots at 10 lbs per slice. Who'd need a gym membership.

Maybe you haven't actually measured the forces you're cutting at. I figured cutting a carrot with a butter knife would be a good demonstration of how 12 lbs is a lot more than it seems. If it's still not made an impression, maybe you should actually go try it for yourself and see how many cutting tasks you do reach or exceed that force. If you're still going to insist that twelve pounds isn't much after that then it speaks volumes more than I could.

[Danke]

Carrots and Allied Trades Research Association

The more you know.