How hard to sharpen is 420HC?

[FortyTwoBlades]

The issue with 420HC is usually a matter of how hard it is. If it's run soft it'll be a pain to get a crisp apex on, even though grinding/rough shaping is easy. When run sufficiently hard, it's a breeze to sharpen.

 

[SALTY]

I love the company called Buck Knives and have plenty of thier products.

That being said, I have some of their older offerings that I have for the life of me are a PITA to sharpen. Maybe the heat treat or hardness was different 30-40 years ago, but it almost turned me off to the brand.

Did I mention that I love Buck Knives and their products?

 

[FortyTwoBlades]

The extremely hard-to-sharpen Bucks were 440C and run on the hard side, and many people struggled to sharpen them on Arkansas stones due to the high chromium carbide content in them, with natural stones still being quite commonly in use at the time. I have sharpened a number of them and diamond stones or aluminum oxide/silicon carbide stones in appropriate grits cut them slower than they do other steels, but don't struggle with them at all.

 

[Robert Ptacek]

I think a lot of the struggle with the Buck knives back in the day were also caused by the semi hollow grind they put on the blades.It was hollowed out above the edge bevel but leaving the edge fairly thick.

 

[Obsessed with Edges]

Yes, Buck's older blades produced up until the early '80s or so were 440C. Notoriously difficult to sharpen on Arkansas stones. But I've especially liked SiC stones or SiC sandpaper for heavy grinding on their 440C in particular. I have an older 2-dot Buck 112 in 440C and went down the difficult path with Arkansas stones, trying to thin the edge on that blade (thick edge grind was another factor which made them difficult). But after trying it with some SiC sandpaper, that stuff ate the 440C for breakfast. Buck later switched to 425M steel, because 440C was also very challenging to fine-blank the blades - tough on Buck's tooling at the factory. Then to 420HC after the 425M, both of which are essentially indistinguishable from each other in terms of ease of grinding/sharpening. Both very easy. I have a 4-dot 112 in 425M, and it's been a breeze to deal with and takes a fine edge easily. A Norton Fine India handles both of them beautifully.

 

[texpat]

Cool thread, thanks guys! I own a bunch of Buck knives myself but I am now just starting to be a little better than lousy at sharpening thanks to things i've learned on this forum.

So, not an expert, and all I have to offer is a sample size of one, the knife below is one of my favorites, it doesn't see much use as it's now the center console emergency blade in the truck. But about 7-8 years ago when I bought it, I didn't have any real experience with the steel, so I took it out on a camping trip and gave it what I call a "basic beating" to see how it would hold up, nothing crazy. Gutting fish and cutting line, cutting some rope for a drying line, digging Morels out of the dirt, a little bit of throwing practice on a stump, making a walking stick, a couple of marshmallow sticks, some feather sticks, shaving magnesium for the fire then using the blade edge to strike the flint (kinda cringy that, but I wanted to know), basically all day and all tasks.

At the end of the day, the edge was duller in many places, and had a little roll here and there, and a microchip from hitting the flint. It would still cut pretty good but needed help. So what I brought with me was just a little Lansky quick-fix pocket sharpener, with the steel on one side and ceramic on the other.

A couple of minutes on the steel side and you could feel it dragging as it cut the damaged areas then started sliding pretty smoothly, switched to ceramic side and did another couple of minutes. Didn't have a strop so took off my leather belt and used it for a few strokes.

I won't say it was back to new again, but it cleaned up great, chip and rolls were gone, would shave hair off my arm again, a perfectly useable edge ready for another day, used it later that night to slice potatoes and onions and green peppers and steak for shish-ke-babs over the fire and it sliced smoothly and cleanly.

So I'm a happy camper, I like how easy it was and I really like this particular blade, a Buck Mesa with nice grippy micarta and a full tang, good size for a small camp knife. I have some blades in better steel that held up a little bit better in that test, but they also weren't near as easy to restore to a working edge.

 

[TheOne45]

The extremely hard-to-sharpen Bucks were 440C and run on the hard side, and many people struggled to sharpen them on Arkansas stones due to the high chromium carbide content

I didn't know the chromium in 440C steel is there to form carbides like in D2 steel. I thought in 440C chrome is there for to make it stainless and stays in the solution.

 

[Obsessed with Edges]

I didn't know the chromium in 440C steel is there to form carbides like in D2 steel. I thought in 440C chrome is there for to make it stainless and stays in the solution.

The chromium will first react to form carbides in proportion to the carbon content in the steel, and then the remaining free chromium will contribute to corrosion resistance. 440C has roughly twice the carbon content of 420HC (1-1.2% carbon in 440C vs. ~ 0.5% carbon in 420HC), so a larger portion of the chromium in 440C will first go toward carbide formation with the carbon. Then, whatever free chromium is left will contribute to the stainlessness of the steel. 440C is still relatively corrosion resistant, due to the 16-18% chromium content in the steel (as compared to 13-14% chromium in 420HC). But a significant portion of that chromium will go toward carbides first, in 440C.

Chromium carbide is nearly twice as hard as the natural abrasive in Arkansas stones (novaculite). So the extra chromium carbide content in 440C is what makes sharpening difficult on Arkansas stones. By contrast, nearly all the chromium in a steel like 420HC will be left for corrosion resistance, whereas the carbides formed will be minimal due to the lower carbon content in 420HC. So, 420HC will be more corrosion resistant than 440C, but much less wear resistant than 440C and therefore much easier to grind & sharpen on natural stones.

 

[TheOne45]

For example, D2 steel has about 12% of Chromium in composition but most goes to form carbides. So, in solution there is only 4 to 6% of Chromium left.

440c has about 17% of Chromium in composition. How much of Chromium goes to form carbides?

 

[Obsessed with Edges]

For example, D2 steel has about 12% of Chromium in composition but most goes to form carbides. So, in solution there is only 4 to 6% of Chromium left.

440c has about 17% of Chromium in composition. How much of Chromium goes to form carbides?

The page linked below has an interesting look at that. If you scroll down the page, it shows 3 micrographs of three different steels, comparing (visually) the carbide volume in each of them. It compares a 420-grade steel to 440C and also to AEB-L. It doesn't specify an amount numerically, in terms of how much chromium in each goes to carbide formation. But instead, it clearly illustrates the physical size of the carbides themselves (very large in 440C, much smaller in the 420-grade steel) and also how widely distributed in the steel they are. And quoted below, a description of the three seen in the micrographs:

( Quoted below, from this page >>>: https://knifesteelnerds.com/2018/07/16/first-stainless-steel-for-knives/ )

"Photo micrographs of 420, 440C, and 19C27 can be seen below. The carbide volume (white/grey particles) is much lower in 420 and the carbides are much smaller, which is because of its low carbon-chromium combination. Because of the low carbide volume and small carbides it has high toughness and ease in sharpening but lower wear resistance than 440 grades or AEB. 440C has a large volume of large carbides giving it high wear resistance but the lowest toughness of the three. AEB is an intermediate grade in terms of carbide volume, toughness, and wear resistance:"

 

[TheOne45]

Thanks for the link. It will be interesting reading.
I was looking at those two links below. They list 440C as high carbon martensitic stainless steel and D2 as alloy - tool steel so I assumed the content of Cr carbides in 440C is much lower as in D2.
By the way, I fI remember correctly knifesteelnerds also have article about D2 steel.

I wondered why 440C would be hard to sharpen. I use diamond files but using classic stones 440C indeed could be hard to sharpen because of carbides.

https://steelselector.sij.si/steels/PK348.html

https://steelselector.sij.si/steels/SIHARD_2379.html

 

[Obsessed with Edges]

Thanks for the link. It will be interesting reading.
I was looking at those two links below. They list 440C as high carbon martensitic stainless steel and D2 as alloy - tool steel so I assumed the content of Cr carbides in 440C is much lower as in D2.
By the way, I fI remember correctly knifesteelnerds also have article about D2 steel.

I wondered why 440C would be hard to sharpen. I use diamond files but using classic stones 440C indeed could be hard to sharpen because of carbides.

https://steelselector.sij.si/steels/PK348.html

https://steelselector.sij.si/steels/SIHARD_2379.html

440C is uniquely interesting to me, because there's such a distinct threshold in ease of sharpening between natural stones and pretty much any other synthetic stone. It's very easy to deal with on AlOx, SiC, diamond, etc. But it kind of slams the door on Arkansas stones if one is trying to do any significant grinding, thinning & reshaping of the edge. 440C is classed as a true stainless, presumably meaning around 12% or so of it's 16-18% total chromium content is providing corrosion resistance. That leaves the balance of the chromium available, possibly up to 5% or so, for forming carbides. Not necessarily huge for wear resistance as compared to something like D2, but it's enough to make a big difference on natural stones, as many who've tried it have found out, including myself.

 

[311climber]

My Buck 420-HC blades get short quickly with regular use.View attachment 2333682

lol are those scored in marks for your sharpener?

 

[tiguy7]

lol are those scored in marks for your sharpener?

I traced the fingers of the sharpening jig onto the blade in order to return the jig to the exact same place. I use a Diamond glass cutter for tracing.

 

[TwinStick]

I think a lot of the struggle with the Buck knives back in the day were also caused by the semi hollow grind they put on the blades.It was hollowed out above the edge bevel but leaving the edge fairly thick.

Yes, ^^^^^ this.

I recently purchased the WORK SHARP PRECISION ADJUST PROFESSIONAL version and literally just got done sharpening/reprofiling a Buck 124 and my Cutco outdoor knife, both of which were hollow grind from the factory.

They both were sharp but would not pop hair at all. I have never liked the hollow grind because I can't duplicate it at home & I don't have the time or the money to send them back to the factory to duplicate the hollow grind. So, I just reprofiled them to a 20° flat ground edge. They are now both hair popping sharp from handle to tip.

I know that a convex edge is more desirable, but I ain't got time for that either. The new WSPAPro is fast,easy and repeatable down to 0.25°, which is pretty freaking accurate.

I just wish they would make one designed and built for great big thick choppers, which is at least 70% of my collection. Maybe next year ?

 

[Another Shepherd]

I know that a convex edge is more desirable, but I ain't got time for that either.

I think that convex edges are more a matter of personal preference.

The new WSPAPro is fast,easy and repeatable down to 0.25°, which is pretty freaking accurate.

I just wish they would make one designed and built for great big thick choppers, which is at least 70% of my collection. Maybe next year ?

The Hapstone V8 together with the new Rail Height Adjuster is almost as easy to use as the Work Sharp Professional Precision Adjust and will handle big, thick knives. I use both. The Hapstone costs more and it may tempt you to buy lots of stones, which will cost even more.