I make tools. I make other things, but I make more tools than the average person and have come to curiosity about not just making this or that spec, but in feel and use, something that will work really well and invite being used.
Over time, I've learned that I will give up edge life for uniformity because I sharpen fast. Uniformity is a pretty simple concept - the more "same" the edge is across its width, the more "same" the surface it leaves will be and the more "same" it will work each time. Uniformity seems to come most easily with faster abrading steels - I think the reason is two fold - they have very small particles in them, even when there are some carbides, and the steels with fine particles tolerate being driven to high hardness. Separately, even with all other things neutral (like hardness), the steel with the smaller particles and some strength will move or break less at the very tip.
In looking at edge uniformity, I discovered something that I used to think was particles *leaving* the matrix -and that is the carbides. What shows up as dots or matte surface at lower magnification in certain steels is actually almost certainly the carbides remaining in the matrix as the matrix wears around them.
So, I figured I'd take some pictures. There are websites like "knifesteelnerds" that show micrographs of various steels, so you can scale the pictures and make sure your own blades don't have carbide coarsening (not a good thing). So far, I've had pretty good "luck" at heat treatment (experience and experimenting and the desire to do that).
So, I'll show the edge pictures at 300x magnification (the pictures themselves are about .01" tall, or slightly less in actual height, or how do you say it - you could fit something in them that's .0095" tall and it would touch the top and bottom of the picture. You will have not heard of some of these steels, but that's OK. What I'm aiming to learn from these is what they look like vs. how they feel and vs. what they'll take for a shaving. There are some steels like 52100 that would seemingly be a good woodworking steel, but it never shows up in woodworking tools and to my knowledge, never has.
Just to be clear, these don't show up when you sharpen, they only show up after some wear, and I believe most are a little closer to round, but the matrix survives behind them to make what looks like tubes as the carbides bust their way through wood. Micrographs of the steels show their actual orientation, and most of the irons that I make are from rolled material, which orients the carbides in the longer direction if are anything other than round (but they are not long straws like these pictures seem to show).
So, 1084 - just above the eutectoid limit. there may be some vintage plane irons that are made of something similar - iron and carbon and almost nothing else. The eutectoid limit is where the carbon in the steel will not be in surplus at a critical temperature, thus what you end up with is a hard matrix and no visible free carbon forming iron carbides.
52100 (1% carbon, a little of other stuff, including 1.5% chromium, but not too much alloying - probably lower alloy volume than O1)
Chinese HSS (The irons with the brazing that you see on ebay or chinese sites). This iron is ultra hard (in this group of four ordered, one was sent south to another forum user who wanted to know what was in them, and the alloying is just short of M2 - but the carbides aren't big or erratic, and the brother to this iron tested 65.8 hardness as the average of three strikes. That actually makes it a better iron as it handles that hardness well (higher strength, lower toughness). In the Chinese tool tradition, the listing said the hardness target was 61 on the c scale. Sometimes the errors are good. I've had others of these that are harder yet and they're too hard to hold an edge reliably, and the average individual would never get them flattened.
More alloying and more carbides than 52100 above - look like they're in layers, and the edge looks less uniform, but whatever shape it wears in, it's actually sharper (it may wear flatter and less round - that's not something I can see from straight overhead).
CTS-XHP (an iron that I made, but most likely the same steel as V11). LOTS of carbides - mostly chromium (which is soft as far as carbides go, but slick. Still harder than iron carbides, so good wear. The edge also looks like uneven layers, but XHP is really smooth and easy through wood - not sure why, but less effort planing. Punishes you if you nick it by being slow honing and hot grinding whereas the simpler steels grind cool and hone faster.
26c3 - a 1.25% carbon steel relatively similar to japanese white 1 (I though this would look super fine, but the surplus carbon does actually make a lot of visible carbides. It's a strong steel though, but not wear resistant - the edge uniformity is pretty hard to beat and so far it doesn't nick that easily). I expect edge life is a little less even than O1 as there's nothing in it but iron (O1 has tungsten and some other bits), and a small amount of chromium and manganese (but the latter two are in small amounts and are bound in the carbon - not free carbides like chromium carbides in 52100 and V11). This is a steel that beginners probably wouldn't love except it gets sharp - really sharp - on anything. I don't think beginners like steels that have low abrasion resistance, though (I didn't). That said, this is an easy steel for learning freehand sharpening because it doesn't hold much of a burr, nicks ground out reasonably fast, but the hardness makes for a very keen edge. Complaints about edge life are usually solved by using a cap iron and increasing shaving thickness for most of the time a plane is in use.
Over time, I've learned that I will give up edge life for uniformity because I sharpen fast. Uniformity is a pretty simple concept - the more "same" the edge is across its width, the more "same" the surface it leaves will be and the more "same" it will work each time. Uniformity seems to come most easily with faster abrading steels - I think the reason is two fold - they have very small particles in them, even when there are some carbides, and the steels with fine particles tolerate being driven to high hardness. Separately, even with all other things neutral (like hardness), the steel with the smaller particles and some strength will move or break less at the very tip.
In looking at edge uniformity, I discovered something that I used to think was particles *leaving* the matrix -and that is the carbides. What shows up as dots or matte surface at lower magnification in certain steels is actually almost certainly the carbides remaining in the matrix as the matrix wears around them.
So, I figured I'd take some pictures. There are websites like "knifesteelnerds" that show micrographs of various steels, so you can scale the pictures and make sure your own blades don't have carbide coarsening (not a good thing). So far, I've had pretty good "luck" at heat treatment (experience and experimenting and the desire to do that).
So, I'll show the edge pictures at 300x magnification (the pictures themselves are about .01" tall, or slightly less in actual height, or how do you say it - you could fit something in them that's .0095" tall and it would touch the top and bottom of the picture. You will have not heard of some of these steels, but that's OK. What I'm aiming to learn from these is what they look like vs. how they feel and vs. what they'll take for a shaving. There are some steels like 52100 that would seemingly be a good woodworking steel, but it never shows up in woodworking tools and to my knowledge, never has.
Just to be clear, these don't show up when you sharpen, they only show up after some wear, and I believe most are a little closer to round, but the matrix survives behind them to make what looks like tubes as the carbides bust their way through wood. Micrographs of the steels show their actual orientation, and most of the irons that I make are from rolled material, which orients the carbides in the longer direction if are anything other than round (but they are not long straws like these pictures seem to show).
So, 1084 - just above the eutectoid limit. there may be some vintage plane irons that are made of something similar - iron and carbon and almost nothing else. The eutectoid limit is where the carbon in the steel will not be in surplus at a critical temperature, thus what you end up with is a hard matrix and no visible free carbon forming iron carbides.
52100 (1% carbon, a little of other stuff, including 1.5% chromium, but not too much alloying - probably lower alloy volume than O1)
Chinese HSS (The irons with the brazing that you see on ebay or chinese sites). This iron is ultra hard (in this group of four ordered, one was sent south to another forum user who wanted to know what was in them, and the alloying is just short of M2 - but the carbides aren't big or erratic, and the brother to this iron tested 65.8 hardness as the average of three strikes. That actually makes it a better iron as it handles that hardness well (higher strength, lower toughness). In the Chinese tool tradition, the listing said the hardness target was 61 on the c scale. Sometimes the errors are good. I've had others of these that are harder yet and they're too hard to hold an edge reliably, and the average individual would never get them flattened.
More alloying and more carbides than 52100 above - look like they're in layers, and the edge looks less uniform, but whatever shape it wears in, it's actually sharper (it may wear flatter and less round - that's not something I can see from straight overhead).
CTS-XHP (an iron that I made, but most likely the same steel as V11). LOTS of carbides - mostly chromium (which is soft as far as carbides go, but slick. Still harder than iron carbides, so good wear. The edge also looks like uneven layers, but XHP is really smooth and easy through wood - not sure why, but less effort planing. Punishes you if you nick it by being slow honing and hot grinding whereas the simpler steels grind cool and hone faster.
26c3 - a 1.25% carbon steel relatively similar to japanese white 1 (I though this would look super fine, but the surplus carbon does actually make a lot of visible carbides. It's a strong steel though, but not wear resistant - the edge uniformity is pretty hard to beat and so far it doesn't nick that easily). I expect edge life is a little less even than O1 as there's nothing in it but iron (O1 has tungsten and some other bits), and a small amount of chromium and manganese (but the latter two are in small amounts and are bound in the carbon - not free carbides like chromium carbides in 52100 and V11). This is a steel that beginners probably wouldn't love except it gets sharp - really sharp - on anything. I don't think beginners like steels that have low abrasion resistance, though (I didn't). That said, this is an easy steel for learning freehand sharpening because it doesn't hold much of a burr, nicks ground out reasonably fast, but the hardness makes for a very keen edge. Complaints about edge life are usually solved by using a cap iron and increasing shaving thickness for most of the time a plane is in use.
