Thread: Chasing fine sharpening

https://i.imgur.com/WmYnODp.jpg

to compare to the spectacularly close pictures in the prior post, the picture here is LN's A2 (the best there is under my microscope) - you can see the grainy look. That's generally attributed to carbides.

Paul Bos (while paul was still there) heat treated CPM 3V:
https://i.imgur.com/GyBDyP6.jpg

These pictures are taken on an older microscope camera than the ones above - not my choice and not to mislead, but rather change necessitated by the first camera not being able to accommodate Windows 10 energy management requirements. Microscope cameras aren't cheap like consumer cameras are. Imagine paying $230US for a basic five megapixel camera module.

O1 from that same older camera (looks like it ran into something before that "something" wore through!)
https://i.imgur.com/NEa8MHe.jpg


Chinese ingot HSS - those tall bumps are stray large carbides. The iron otherwise did well and lasted with 3V but was more pleasant to sharpen. they'd be half that size or less in good quality M2:
https://i.imgur.com/GNBrMU0.jpg

CPM M4
https://i.imgur.com/UibN1ao.jpg

Tsunesaburo blue steel 1, as mentioned in the other thread:
https://i.imgur.com/dhmKa79.jpg

I don't know why, but I expected this to be extremely uniform. Larrin thomas later showed micrographs of blue steel. The tungsten added to them, which was the first choice for carbides a century ago due to its ability to be dissolved at forging temperatures rather than coarsening....whatever the case is, the tungsten carbides beyond the small amounts in O1 just don't lead to uniform dispersion. Instead you get big carbides spread far apart, and somewhat random in size.

The result was that the steel only matched O1 in planing edge life, but the surface wasn't as good. I got multiple "mine doesn't do this" when posting that result, but the correct answer is "I don't notice it". It's not noticed because you really have to do a side by side test to suss these things out. Larrin Thomas showing micrographs later really helps show the actual carbide dispersion in heat treated steel to explain what shows up on the surface here.

Magnacut - double the magnification, new camera. Notice the lack of the grainy look.

https://ofhandmaking.files.wordpress...1-wear-300.jpg

I was at first confused by looking back at the 3V pictures. I thought 3V had AEB-L like carbides, but it doesn't really - they aren't as nicely distributed.

what I've found is carbides around 1 micron or so begin to be difficult to see vs. a smooth surface:
https://i0.wp.com/knifesteelnerds.co...pg?w=750&ssl=1

And 3V
https://i1.wp.com/knifesteelnerds.co...pg?w=750&ssl=1

and a wear picture of AEB-L
https://ofhandmaking.files.wordpress...2/08/aeb-l.jpg

The camera software was confused by the smudgy smooth wear surface.

it's pretty easy to look at actual micrographs (look for the bright dots -they're carbides - the coarser they are, the coarser the wear will be. if they're vanadium, they break pretty easily in use - still not really excited about vanadium carbides in woodworking tools unless those tools are for turning dirty wood).

https://ofhandmaking.files.wordpress...large-dent.jpg

One last picture just for sport - when I got the magnacut iron, it was suspiciously easy to sharpen. From my experience, easy to sharpen means something is off even if the steel is something simple like 3V or Magnacut with no large carbides.

I couldn't plane without finding dents in the edge, and asked Larrin if I could send it to him to hardness test. And then I trusted my experience instead and before sending it, ground off the entire bevel to get away from steel that had been ground when it was made, and this behavior stopped.

of course, once the soft part was gone, then the iron was also much more resistant to sharpening stones (not so blatantly easy to sharpen). Not too long after this, i bought a hardness tester and found the middle of the iron to be 62.5 hardness. well in spec. it's unlikely that this is a one-time thing, but most people buying tools won't notice this. they may notice that over time, the iron gets harder to sharpen. Edge life in soft state would be no better than O1.

To tie in why hardness matters here with the dent picture - strength of steel (resistance to denting or deflection) is highly related to hardness. The defective nature of the edge made it so that denting/nicking was spectacular in things that generally wouldn't dent another iron. it wasn't immediate on the first stroke, but you can see not much wear has occurred yet.

The wear pattern of what has worn is curious - i don't know what causes this - I would guess it's vanadium carbides fracturing and then that area grows leaving some other parts unaffected.

if you could just get carbides to not ever fracture, edges would be several multiples of "normal" steel. Unfortunately, it's not to be with vanadium.

I don't see the same odd breaking from chromium carbides - they're less hard. I'm sure they break more easily than the steel matrix, but it's not as blatant.
https://i.imgur.com/vGxX2OJ.jpg

That is the edge of XHP, or what V11 would look like after wear from planing very close up - the carbides end up sticking up out of the matrix. They are chromium carbides, and the edge looks less fine because of them. The volume does affect edge stability for nicking and chiseling, but it does not affect sharpness. If anything, it feels a little more sharp as it wears.

lastly - 26c3, a plain but very high carbon steel. it looks less uniform than O1 or 1095, so you'd assume that maybe it wouldn't make a great razor. Except it does - that's the target market for the steel. The carbides are fewer and look similar to V11, but they are iron carbides and tougher. Edge stability is superb. Abrasive resistance is poor - slightly less edge life than O1. In practice, the ease in sharpening makes it not matter much. I'd rather use it than anything PM I've tried so far. The nuance of this is lost on beginners - uniformity and stability vs. bars on a sand cylinder wear test - but it doesn't matter much. Nobody is going to try to make irons commercially out of 26c3 - it needs a very fast quench and the places making all of these new irons (zen wu) are relying on hands off vacuum furnace heat treatment. Fast quenching (and dealing with warping) are a lost skill.

https://i.imgur.com/z4QRWVU.jpg

What makes a great razor also makes a great chisel.

apologies for the tangents, by the way. The discussion of PMs and the touts that they get came to mind, especially when we often hear they are finer than other steels. The finest structures in the pictures shown previously are not PMs, except magnacut is pretty good (AEB-L, 1095, O1) are all ingot steels (old school melted and cast into an ingot and then rolled into flat/strip steel). AEB-L is so inexpensive, it's silly. the composition prevents enough free carbon in solution to ball up with chromium in large carbides.

Coincidentally, this is the feat Larrin performed with magnacut, sort of. he managed to get vanadium to absorb the free carbon at levels where carbides would remain small - like with 3V and 4V - and not have the carbon get tied to chromium, which remains in the lattice of the steel to prevent corrosion. I can't overstate how interesting and new that is, and he had to stray from metallurgical software to figure it out. AEB-L does it by composition, and to some extent, so does magnacut. In the end, the carbides are even smaller than 3V and 4V.

Just browsed the whole thing again - I forgot that the carbides are a combination of niobium and vanadium. I don't want to get into larrin's fascination other than to say toughness tests on a charpy tester (swings into a pre-determined sample size and checks how much energy was taken from the pendulum that blasts through the sample) favor smaller denser carbides, but usefulness of that in woodworking is less clear. Usefulness for a knife maker not wanting people to send back knives broken in half is much higher. O1 is a low toughness steel that can be easily broken and we don't see floods of the chisels broken in half. Same with PM V11 - relatively low toughness steel, but we don't use them for breaking and entering.

the virtue of tiny carbides beyond toughness is to draw in knife makers who like to make high wear stainless steels but hate the way large carbides polish. they are a pain, and thus when you see big knives in steels with large vanadium carbide volume, they will be ULTRA expensive if the whole knife is brought to a bright tidy polish.

For woodworking, again...hard to translate.

And after I tested the Magnacut iron, as much as I was enamored with the technical feat, it doesn't unseat simpler steels in actual work and it still abrades slowly on stones, relatively no faster vs. its edge life. AEB-L driven up in hardness (where it approaches magnacut in edge life) is similar - once you chase it into a hardness where it wears long, then it's a pain on the stones.

but that sort of gets back to the question fergiz asked - where do you choose one over the other. I think the buffer will always create a uniform edge more easily as even a rotating MDF disc will lead to some deflection (pictures later maybe, I just did it) - and it's one thing to spend a minute or two watching a wheel rotate while you're using it, and another to choose anything other than the easiest way to get great results in the context of work when maybe dust has settled on things. clean MDF and a small abrasive can make spectacular microscope pictures, though - with little scratching big enough to let light into the scratches (they're still there, they're just too small for light to go into and bounce back at a different angle. The definition of a bright polish).

Had a day off (waiting for plumbers and sparkies), so I tried out the diamond dust. I sharpened a chisel and a plane blade and compared before and after. I think it works!! Made myself a little paddle.

Sent from my SM-G986B using Tapatalk

So... From my own tests, I can't abide steels that fail via large chunks breaking out of the apex. I had several D2 knives do that when butchering deer, and it drove me nuts. I have had chisels do the same... That earns a trip to the box of shame.

I have run into more than a few chisels which seem to have a thin layer of mush on the exterior hiding a much harder core. It is fairly evident when flattening backs, as the sandpaper cuts extremely fast at first and then slows considerably, even factoring in a sand paper change. These tools also demonstrate significant improvements after several sharpenings.

In my own tests, I have experienced some "strange" results that indicate grain flow direction is considerably more important than several other factors. Conversely, bulk hardness by itself isn't really an accurate predictor of woodworking tool performance. This was driven home spectacularly by some cheap chisels made via stock removal from drawn rod rather than drop forging. Their edge life doubled, and in some cases tripled many "higher quality" drop forged models. I believe this is one of the reasons Lie Nielsen chisels are widely regarded as high performers, even though the alloy may not be optimal. They are simply machined from drawn rod, and as such, grain flow in the steel is not impaired.

But those are the sort of things you learn by testing tools against others. You would think that manufacturers would want to know how their product shakes out against the competition, and then ask why is theirs better... But given what I'm seeing across multiple market segments, perhaps I'm wrong, and what really matters is good marketing copy.

grain direction is vital. it's vital for directional toughness, especially in rolled steel, but it also varies a lot from one steel to the next. For example, CPM 3V has a reputation for being very high toughness. It's longitudinal toughness is right up there with other matrix stuff and lower carbon plain steels, which is sky high - you can bend them and bend them and bend them and they won't break unless their hardness is pushed.

However, 4V was thought to have better hardness potential and still be tough, but it's toughness is half or less of 3V, and the kicker is 3V has an extreme bias in its longitudinal direction, but 4V doesn't. Why? who knows.

chisels forged from round bar need to be drawn out in length, and chisels made from flat bar will have poor edge behavior if an arrow representing grain doesn't run through their length.

Larrin has a big talk on knives in terms of why the bias doesn't favor being perpendicular to the edge, and the answer is simple - blades would break more easily and breaking is worse than somewhat poorer edge performance.

I don't see large sections of steel missing, or big break outs, lets say, but under the microscope if you can see voids a thousandth or several thousandths where a large stray carbide breaks out, that's going to be an edge that's crap from the start.

I don't think longitudinal carbides, which are where cracks start, though, make LN's chisels more favorable. Edge stability improves if those carbides are made smaller by spheroidizing them. I think LN's chisels perform well because the stock is decent and they're hardened and cryo treated properly. if there are drop forged chisels (they are forged from rod also and the grain direction isn't spoiled) that perform poorly, something is wrong with them.

I'm not sure at this point which has more refined carbides - bar stock or rod. Bar stock that's in very large thicknesses goes through less forging as it's rolled fewer times, and the grain in thinner bars will be refined (but the carbides still tubular in the direction of the roll).

I'm not sure how what happens with the drawn rod, but I'm hoping to start making integral bolster chisels soon, which is only practical to do starting with round rod. It'll be interesting to see how they compare to bar stock chisels that I've done minimal hammering on other than shaping.

Hardness is pretty important in chisels, but overall grain size (since it's much larger than the carbide size on small carbide steels) is also very important. There's no saving a chisel that's had some issues with grain growth - other than thermally cycling it and rehardening.

I should add when we're talking about longitudinal toughness, it doesn't seem to have that much to do with edge stability. A2 is not a high toughness steel. O1 is not a high toughness steel, etc, but they make good chisels. 3V is an extremely high toughness steel but the edge stability isn't as good - it lack carbon. It's hard to break bending sideways, but we don't do that with chisels.

I polled larrin about this - why isn't there a metric to describe how a fine edge holds up when hardness and toughness or some combination of the two often don't do a good job describing it. He said the term "edge stability" is pretty standard. I'd have to go back and look up what he described. Razors have a lot of edge stability to impact, but are not tolerant of bending. They would be described as having high edge stability. Same thing with white steel japanese chisels.

Most of the drop forged chisels are made of lower carbon steel than A2- 0.6% carbon, perhaps with extra Mn is fairly common.

I've seen what you describe in terms of "a good chisel inside of a wrapper of bad steel" or the same with a knife. that's probably decarb if there is a layer all over. I got some chisels from HF years ago for $7 that had " a good chisel inside the chisel shaped objects once you got to the good chisel inside".

they are drop forged and 59 hardness. Which is right in the wheelhouse for 0.6%CrV steel. 62 would be the same result for a CrV rod with 1% carbon going through the exact same processing equipment. I believe the attestations of aldi chisels with 62+ hardness are based on someone doing a run of 100crV steel.