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Discussion in 'General Knife Discussion' started by Gil P., Jun 16, 2020.
Which is more likely to keep a thin edge without damage like rolls or chips?
The two steels are in a similar category for properties. The heat treatment and edge geometry will matter more for performance than which of those steels you have.
May not get specifically to your exact question, but good information from a respected maker none the less.
Here is a comparison of these popular PM tool steels in production folders. Special thanks to Darby for letting me borrow his Cruwear Millie for so long. I'm missing the 4v but I owned one in the past and currently make knives from it. In a production knife from spyderco it will be softer in hardness than the Rex45 but may out cut rex 45 if the 4v is at sufficient hardness due to having the advantage with slightly more carbide volume and more harder Vanadium Carbides, yet similar Strength and stability, yet on the softer thicker end may have more obtainable raw toughness at lower hardness depending on HT and Geometry. Here is M4 vs Rex45 https://youtu.be/WOpu13O_OFE M4 vs K390 https://youtu.be/TI53ziibeiQ More M4 vs K390 https://youtu.be/E-c3LxQbcqg
I've broken a tip off a 4V Manix 2, but never on my Cruwear Manix'es (spell?).
For whatever it's worth, as a user, 4V "feels" like M4 to me, 3V "feels" like Cruwear (all CPM).
Some good info here. I agree with Larrin on the point that hardness and geometry will likely be the deciding factor between the two. In Spyderco's, Cruwear has been coming in anywhere from 61 to 63.5 or so. 4V has been 62.5 to 64.5. Assuming geometry is equal, the one with the higher hardness will give you greater edge strength. 4V seems to be harder more consistently from Spyderco, so that may be your best bet if you're going that route.
I'm not sure on where I will get the knife from yet, but it will be a fixed blade for camp use and processing deer.
I asked this question because I brought a Bark River Aurora III 3V edge down to 4 or 5 thou and got chips and rolls after light use. I measured using a pair of digital calipers on the edge and that was consistently the last measurement I would get before the calipers slipped off the edge.
I have two other knives from Bark River on 3V and those measured 9 - 10 thou using the same method. I don't get bad chips or rolls with those knives.
I was looking for an upgrade in what appears to be an edge strength shortcoming of 3V.
Allow me to make a couple of introductions. Many others on the forum as well.
Carothers - Delta 3v
Razor Edge Knives - Cruwear
I've got knives from Big Chris in 4V, 10V, and Z-Wear, never had a problem with the edges. Facebook or Instagram is the best place to find him.
Absolutely the best performing knife made on the market made from 3V is a CPK (Carothers Performance Knives)
I'll have to check out Big Chris' knives. Right now I'm thinking of giving CPK a call.
I'm the meantime, what should I do about my chippy 3V knives?
Right now they are all sharpened to a 0° convex. Should I add a secondary V edge? Take off some more material and fatten up the edge?
Measuring the edge width to thousandths of an inch can be a challenge, especially with convex edges, especially with thin convex edges.
If you're getting both chipping and rolling, the heat treat is most likely the problem. But from your earlier post, you say the edge width is very thin, so look there first.
There is no such thing as a 0° convex edge, and if you mean that you have a full convex grind, then your edge with is the width of the spine.
I'm guessing that you don't have a full convex grind, but that your edge is extremely thin. When you have a convex edge, you don't really know what you have because there is no easy way to measure it.
You might try putting on a 30° inclusive V edge. If that gives you problems under harder use, add a 40° inclusive microbevel. If it still chips, the heat treat is probably the problem.
I may try the v edge. You are correct about the convex. I removed the secondary bevel that come on it from bark river.
I hope it's not the heat treat.
Not being sarcastic here, but it would seem to me you've already answered this question for yourself. If you brought it down to 3-4 thou and it failed but you have others at 9-10 thou that don't, then I'd say you need to reset the edge to 9-10 thou. I take this as you found an outer limit that that specific knife at least can tolerate.
You're right. My plan is to use it again and if there are still problems, re sharpen with Venev OCB stones instead of water stones like I was. I'll make the edge fatter while I'm at it.
I made the edge a little fatter on Venev OCB stones and its cured the problem. Now the edge measures about 8 thou. I still got very slight rolling batonnibg through a less than wrist thick log. I think I'm right on the edge of edge thinness / durability for this steel.
I'll leave it as is and make it a tad thicker when it gets dull again.
I couldnt get it as sharp on the Venev stones as I could on the Chosera 3000. It could be due to the fatter edge or I'm just not as good at sharpening on the Venev stones. They are the skinny short ones, not the full size bench stones like Chosera
The convexity can be measured with a laser goniometer.
That's correct, but the problem is that the laser shows a range of angles. Each angle represents the laser beam reflecting off one point on the edge. Light travels in a straight line, so the initial laser is one straight line, and the reflection represents a second line.
Each point on that convex edge will have a different angle.
You can visibly see this phenomenon as a crescent-shaped reflection on the goniometer's grid.
The problem is that there is no easy way to represent this multiplicity of angles -- or state it simply, as you would for a V edge at, say 30°. Unlike V edges, convex edges are difficult to describe. When someone says they have a convex edge, it doesn't mean much. It could be extremely acute. It could be extremely obtuse. Or it could be indistinguishable from a V edge without the use of high-definition measuring equipment.
A convex will show up as a "dash"
The outer ends of the "dash" are the angles at the actual apex.
A convex edge will show as a crescent line, from the most obtuse part of the edge at the apex to the most acute part of the edge, which is near the shoulder. This explanation is the company's own position, which is described in this correspondence form the company a few years ago:
"The device cannot ignore anything on the edge, its simply has to reflect everything that is there.
"So with a convex or a concave edge you will get the full changes of surface angularity. The problem is that it cannot distinguish between convex and concave. So if you have a convex edge as shown in the attached sketch you will get a crescent shaped reflection ( if it’s a ground edge) from the minimum to the maximum angle of the curved surface. If it’s a polished edge with no grinding scratches, you just s a straight line reflection from the minimum to the maximum angle."
Do you own one?