David Weaver Chisels

Re: Reality with the steel

Nice post.

I see where Dictum offers plane irons in SK4, Japanese "blue paper steel", or HSS.  Nice to have a choice:

DICTUM Smoothing Plane No. 4, SK4 Blade | DICTUM planes | Dictum

Decent looking Bedrock clone.

Re: Reality with the steel

“Very old tools were softer most likely for industrial reasons ...”

This reminds me of stuff Larry Williams used to write about double iron planes. It could also be because they knew what they were doing and actually wanted them softer. 

Re: Reality with the steel

I edited that to be shorter before the long post I already put up. 

before editing it, I wrote that there are probably a bunch of reasons that they were softer and none of us will ever know for sure why things were the way they were. of course they wanted them softer, or they would've been harder. 

It is absolutely the case that if you choose 0.8-1% steel and try to chase high hardness with it, it doesn't perform better. 0.8% steel will perform (getting acceptable hardness) about the same at 60 hardness as 26c3 will at 64 or O1 at 61/62. 

If I edited it out, I also mentioned mahogany and woods that hadn't seen kiln drying. Of the chisels that I worked with in the unicorn article, the sorby chisels are fine if you use them in softwood or good quality mahogany. I don't think they were made to do that, I think they're made with lower carbon steel because it's easier and hits an ASTM spec or something (to be harder to break for site work). Cherry is enough to make them look bad. 

All that said, if I dropped a 64 hardness chisel on someone using sandstones and slate, they'd have not been able to deal with them. And the quality of 1800 razors (which are higher carbon) isn't very good, so I don't know how much harder it was for the English to make steel that had significant excess carbon. 

Voestalpine doesn't have a problem with it, but they're also able to roll their stock easily. It isn't the case that any 1800 steel was better than voestalpine or hitachi's offerings. 

https://knifesteelnerds.com/2019/07/22/forged-vs-stock-removal-knives/

If there is some remaining myth about how much better the steel was due to forging, it's addressed above. Knives may have some case in very extreme cases where a forger starts with a large ball bearing and heavily forges it over and over to try to get rid of the original grain orientation. But Larrin changed his statement about heat treatment based on what I sent him - the forged samples he's received generally suffered from grain growth that wasn't properly addressed or forged steel that didn't undergo a full anneal (or both). larrin suggested to me that forge heat treatment won't result in a good sample. 

The last time he sent an article out to patreon subscribers, he changed that statement to "I wouldn't recommend it as I've only seen a success rate of about 20% on forge heat treatment". 

it's fair to say that:

1) I'm not a re-enactor and my chisels and planes adopt aspects of certain time periods

2) I'm not inclined to argue further with people who can't produce a sample of steel that matches mine. that may sound harsh, but at this point, why should I. I've probably owned or tried more than almost anyone on here, I've made more tools than most (especially by hand and I), and looked at enough to continue to be curious but be a little bit dismissive until given a reason not to be. 

larry and I don't have a lot in common. he's probably a better guy than I've given him credit for being - that's a personal fault of mine, so that statement is not a slight to him. I will speculate, but speculation isn't proof. Speculation is necessary as a first step if you're looking to prove something, but 1800s steel isn't going to be a specialty of mine with the quality of rolled material like voestalpine's and the bohler and starrett O1. 

Re: Reality with the steel

Easier to straighten a slightly rolled edge than grind back for a missing chunk at the tip.  

Re: Reality with the steel

David,

I have a question about hand forging versus commercial forging and furnace heat treatment:

1st….You decisively beat the commercial hardness/toughness tradeoff for 26c3.  ‘Decisively’, because Larrin conducted the tests and just sent you the results.  By ‘beat’, I mean your forgings had higher toughness and hardness than the posted commercial expectation.

2nd….How did that happen?  Same steel stock from westalpine.  Same testing by independent source.

3rd….My interpretation is that your hand forging/heat treatment was better than by-the-book commercial.  Not sure if you used multiple heats on those test forgings, like some of the Japanese smiths do.  Any case, was it not the hand work that produced the superior result?  And if so, is that not an example of hand skill being able to beat the cookbook?

Wiley

Re: Reality with the steel

1,2) I did- same steel, identical composition and the batches are so clean that the variance is a tiny fraction of the actual tolerance - below the tolerance of any listed steel of any type for contaminants by a wide margin. 

I can only guess why that is, but Larrin hinted at something. I am focusing on heating to critical and then another full notch past there. I tried heating samples to nonmagnetic and then two big steps after that with O1 - without a soak, the steels that are slightly overheated end up harder, but the overheating is only very quick and it is a small fraction of the time that it would take grain to actually grow. that means I could have more than one shot at heating if a chisel warps too much and not appreciably grow grain. when I mentioned this, Larrin said that it is common for fast induction heating to heat well past where a furnace soak would be. I don't think it's by accident that such a thing is common in industrial induction heating processes. 

Here's what larrin also hinted at - you can chase higher hardness in a furnace with a cold terminal temperature (like liquid nitrogen if desirable) to increase hardness some and be safe that you're heating enough, but a higher soak temperature allows more carbon to dissolve in the matrix than - I guess - the eutectoid limit. The result is the matrix loses toughness. 

I think this is where the results are gained by forge heat treatment - I don't have to soak the steel in a slow heating furnace to get well past critical, get high hardness - very high out of the quench, and the lack of a longer soak time means my excess carbon remains in the carbides and not in the matrix. 

Anyone reading who wants to see what carbides look like separate from the matrix - this is 52100 - I can't find the 26c3 picture, but figure half as many little dots standing proud. this is what an iron looks like after it has planed for a while - it's the back and the cap iron is holding the shaving against the iron tip - the matrix wears away faster than the carbides. 26c3 does show a lot of these, though. 

Following what Larrin said, it seems reasonable to try to quench as fast as possible and terminate the quench temperature quickly as low as possible (that's the freezer for me) to maximize hardness, but to do a quick heat to keep excess carbon from dissolving into the matrix. 

this is all after-the fact guessing, though. I only sent samples more or less due to critics here. I can take a chisel done with this process and test it in any reasonable test against old and new chisels, and if it betters them, there's no great need. I can also identify hardened plain steel pretty reliably between about 60 and 65 hardness with a washita, india and natural japanese stone. that's how I guessed at 61/62 and 63/64 for O1 and 26c3. I had no idea if my guess was correct, but just suspected it based on the known hardness of novaculite and knowing that overhard japanese chisels can be a real bear on a good natural japanese stone - an impractical bear. 

3) I hope it is - what triggered it was trying the steel with one quick hard heat and then quenching. It was good. But it wasn't better than a ward chisel, and wasn't quite as good. After reading about shrinking grain and the idea that hardness could be driven higher with smaller grain and the same toughness, I tried verhoeven's triple quench Idea. I may have read it wrong. Taking the steel to critical and quenching it three times grows the grain a little in files and in other steel, but if grain is really large from forging, it probably shrinks the grain a lot. 

I have seen other people talk about descending heat quenches before the final quench, but that seemed fiddly, so I learned to identify a slight color shade prior to when a steel becomes nonmagnetic and quenched. that can be done in air or with quench oil. I am too lazy to wait for air cooling. larrin suggested this may not be doing anything other than modifying carbides. I think what I'm actually doing is heating to about the point where transition starts and then quenches. 

then after the last heat, I do the fast high heat and a quench. How high? a mid orange - a temperature that you would never allow the steel to stay at. Snapped samples show  no increased grain size. I can take a nicholson file and actually shrink the grain on it, too, even though they're well done at the factory - very well done. The carbides will make the snapped grain on a chisel like this look a little bigger. 

Tools get seven total heats.

3-heats - I shape the steel at the forge. I don't heat it to forging temperature, but a little shy of that and hammer it closer to black heat, but it gets reheated each time to critical in the forge, so no damage remains from that. I don't hammer it enough to crack it. that cuts down on the amount of grinding I have to do, and I just like to do it. these are done with descending temp and the last heat doesn't get too much hammering- "cold packing" doesn't lead to an improvement and may do the opposite. 

then, i do basic grinding after the steel is cool and forge weld on the bolster. 

Once the steel is ready for heat treat, then:

* 3 subcritical heats and quenches

* one fast heat, and the quench process

it sounds like a lot of steps, but it's part of making the chisels and it takes very little time. The subcritical heats don't need to go to full room temp, they just get quenched quickly a good bit past black and then back in the heat. It would take far longer to do it with a furnace and I can keep track of two at a time. 

I haven't made O1 chisels like this, so no clue if they would improve. The samples that I sent all got the same heat sequence, but no forging, because I didn't want to fish with the grain and not be able to compare to larrin. I doubt I'm doing enough forging when shaping (halving the thickness at most, but a little less than that) to change the grain orientation. 

I don't show any advantage over forge results with O1 or 1095 other than I get higher hardness and slightly less toughness than expected with 1095 - it just needs to be tempered a little further. the cost of 26c3 isn't enough (and the toughness a lot higher) for me to consider using 1095 for anything. 

there are a bunch of other little things that drove me toward trying 26c3, but I anticipated that it would be hard and not tough. I was wrong. Fortunately. it's just a good match for the process and the process was backed into just by snapping samples and testing results. 

Apparently you missed the point

The goal is to have a chisel that does neither without treating it tenderly,  which is apparent to anyone making stuff. I have been using David's chisels for some time now and the edge is the most durable of any chisel I own for the work I do in cherry and walnut.  No doubt misused these high hardness chisels could break.  Used normally they don't.  David worried about corners chipping but they have not in my hands.  And they don't deform like any softer chisel does in my hands. High hardness is essential to resist deformation.  The trick is to get high hardness while preserving toughness.  

The bottom line is that David's research and experimentation has produced an exceptionally durable chisel that can be readily sharpened by anyone not stuck in ancient sharpening technology.  What's not to celebrate?

One would hope that the details provided will encourage someone else to replicate this work.  David's success should be sufficient motivation.   

Re: Reality with the steel

OK, so the magic came from the triple heat grain-shrink procedure.  Thanks,  Wiley

Re: Reality with the steel

I have used chisels from the 1820s for 45 years. I have never seen a “rolled edge “ on one of these chisels. 

If you are getting “rolled edges” on this type of chisel, something is very wrong. 

Re: Reality with the steel

It appears to be. There's another potential route to the modified structure before quenching - a very slow anneal. I didn't read much before experimenting - it gets in the way unless you're addressing a specific problem, so the idea of modifying some basic things just seems reasonable. The long-held wisdom is that higher carbon steels are harder to get right. I think that's backwards, but it may have to do with what people are thinking when heat treating. O1 is advised as a steel that's hard to get right. I've had trouble getting it wrong. 1084 is the suggested starting point, but it's actually less easy to do well unless you give it a simple anneal and heat and quench - and the quench needs to be in parks to be useful. Otherwise, it's subpar. 

Point being, I checked larrin's page about annealing and structure after a steel cools and there are industry methods to cool extremely slowly to get a fine carbide structure (spheroidized). The follow-up to that is filled with comments about some steels being hard to get completely transitioned in a furnace at suggested temperatures, but none of that discussion applies with a forge and careful initial heats and an overshot on purpose to quench. Another good reason to experiment, discern and solve problems rather than reading something not directly applicable hoping it will apply. that, itself is a big problem with people heat treating by eye - the advice always starts from someone who is trying to adapt what they learned using a furnace. Only larrin has confirmed that my desire to overheat for very short duration to get better hardness is actually in practical use elsewhere (industrially), but had he not confirmed it, it wouldn't matter - I had results in hand with very noticeable hardness difference and no lack of toughness. Everything else you read talks about drastic grain growth - assuming that it will occur because it would in a furnace. 

The point of this with the short heats is in discussing a slow anneal in vermiculite with lower carbon steels, Larrin mentions that higher carbide content makes it easier to get the transformation to fine carbides as they will seed the transformation from pearlite structure better and tolerate faster cooling and still do it. 26c3 just seems to be ideal, 1095 and O1 work "well enough" and I had poor results from 1084, overshot hardness for tempering temperature, and toughness way low. Never experimented with it or snapped samples, though, so no reason to expect it would like the same process. Or put a different way, 26c3 seems to get the benefit of modification due to the high carbide content whereas maybe the classic blacksmith's method of overnight anneal will work better with steels like 1084 and below. 

1095 itself suffers from a lack of alloying - but the versions actually used in commercial knives (a 1% steel with small additions of chromium and vanadium and a few other things like nitrogen) aren't sold in volume - I doubt many knives are actually made of true 1095. Toughness is low enough in 1095 that at same hardness as O1, it will chip more often in regular planing, and it doesn't become very tough just by tempering further. I see exactly one source for 50100B sharon steel that was a special order and is sold retail - at a size not ideal for me, but seeing the poor results from 1095. I just ordered some - not for chisels, but to see if I can make a good very plain plane iron.

Bill's right on the money with his last comment - the discussion around all of this wasn't to brand anything for sale. It was to try to find something that works well so that other people would do it, and get past the myth that it's not doable. The discussion makes the process sound more complicated than it is. We use tools - when the tools work better, it makes it easy to tell that the results are better. Testing to get formal results can follow later if needed. when I make a chisel, I can do something similar to proofing a rifle barrel. Use it with an unreasonably stiff malleting. Anyone else could do the same thing. 

Re: Reality with the steel

It's not that important and I will duck back off of the forum after this thread, but you are right. 

In the process of making tools, I encountered steels too tough or too soft. 52100 is so tough that the edge will begin to deflect but it won't let go - at higher hardness than the early 1800s chisels are "dry" and let go of anything first. 

I had high hopes for 52100 because of its toughness, but it increases the edge cross section immediately where as very tiny bits of a stronger but less tough edge steel (or even equal strength, but less tough) will not increase the edge cross section. 

Straightening a bent edge is something that sounds nice. to actually work better is something that would have to rely on circumstances that don't exist. It always created more work malleting, even before the rolling was severe and the only way to get past it is to set the edge up in a way that it wouldn't roll. That's a concession in initial edge steepness that also causes a problem with effort. 

All good chisels don't chip that easily, and when they do, whatever they let go of is gone and not large. The same is true for a good slicing knife. 

" it increases the edge cross section"

>>but it increases the edge cross section immediately where as very tiny bits of a stronger but less tough edge steel (or even equal strength, but less tough) will not increase the edge cross section. <<

probably not obvious what I meant. Extreme toughness allows the edge to roll even in a hard steel and even though it starts small at suitable hardness, it holds on and propagates. It also seems to go deeper than chipping does, or at least as deep. 

when an edge is softer (like too soft, not 1820 soft, but like not enough carbon 2022 soft), in my planing test, the softer the iron, the deeper the damage. It's problematic on plane irons, too - the deflected edge won't enter wood. a few small chips and you can keep planing (it always lowers productivity if the chips split the shaving - by a lot). When I ran into maple, just a few small dents with deflection of a few thousandths each prevent a plane from continuing to cut even in an ideal test. 

Nobody probably cares much about this stuff because the actual use of hand tools is far less than the talk about them and purchasing of them. 

They would've affected income 200 years ago. 

Re: Reality with the steel

Crappy chisels most likely.  But they're what I have.  I also hone very low, and touch up frequently.  End the end it's all good.

Re: Reality with the steel

"In the end..."

PM-VII didn't like how low I honed either.  The only chisel I own that does, is one David made for me.  

The only one...

That is the only chisel that I ever finished in O1 that I can recall. It was right at the time that I realized I'd never find a constant supply of heller files that are 1/4" thick and not exorbitantly expensive, and 1095 wasn't cutting the mustard. 

Not sure when I sent that to you ,but my machine planer still has three or four more paring blanks laying on the bed marked with marker - which is maybe a suggestion that I don't need that much, but one never knows when they'll be forced to make something they don't want to (I have two of those things on the horizon - it'll spin up for them). I have burned plenty of electrons with a grinder, though, and wouldn't be without it - there's no religious reason the planer doesn't run. 

At any rate, it's probably the only O1 chisel, and it's also the only chisel that got tempered with food. Over-tempered a little thanks to the mrs. deciding I was in her way and ratcheting up the oven temp for baked potatoes. I thought for sure it would be overtempered and roll, but it passed the roll test without issue (hard malleting in something really hard). 

O1 has a pretty wide acceptable range, though and makes a good chisel (375-425F-ish temper- ballpark 60-ish hardness or just a tad more). 

There's a reality for a junk maker like me, too - there's no order list and if one does go out as a dud, it's not much work to just make another one. I can't make a case that 26c3 is practically better, but it is a little better and is probably inaccessible to do good work with it commercially, too. Regardless, O1 is a nice steel and it makes nice tools, and for practical purposes, it's as fine grained as anything - snapped samples look like clay. 

Re: The only one...

Well it works great!

Re: Reality with the steel

The biggest reality for me is the wood itself.  If I only cut today's pine, I could use blister pack chisels.  I work with mostly cherry, beech and walnut that I cut myself.  O1 is all I ever need.  I tell the embarrassing story of making a plane blade that I did the heat treating outside in winter.  Most of the blades cracked, one made it to a plane.  It cut fine, and then I hit a knot in a 2x4 at some future date, and was surprised to see that I bent the edge.  I don't know how hard it was, and that is the point.

If I worked mostly tropical woods like ebony, coco, I would probably prefer something else again.

I bought my first blue steel tools, and everything else, in the early 80s, and started seriously into making tools around 2000.  That is earlier than most.  There is no question people overthink this stuff.  Back in the 80s, you couldn't get good tools, so there was some point to looking in esoteric directions for unfamiliar tools, as per Japan.  Now you can take a wad of cash and buy everything from one supplier.  It's mainly silly at this point to be thinking about it much.  There was a point in the 90s when due to one thing or another (certainly not what they wanted) when LV didn't sell any dovetail saws, or (even setting the bar low), any professional grade planes or chisels.  That world is long gone.  I don't remember when that was, but it would have been around the time FWW did that article on how to make your own dovetail saw, from a gent's saw, by recutting the teeth so they were twice as coarse.

I'm not sure...

...if you're calling this as a hobby a waste of time or whatever it may be

I guess if someone thinks a toolmaker who wades into the details is wasting their time but making furniture for a hobby and needling away at joints isn't, or buying japanese tools or whatever else, I don't really get it. 

Even making furniture for ourselves is a nonsensical thing, unless you can find *really* cheap material. I've never been able to find good materials as cheaply as I can find discarded old furniture, and some of it surprisingly wonderful. 

I'll rise to that bait.....

"Even making furniture for ourselves is a nonsensical thing" Not for me.  I have the time and skills.  Daughter and granddaughters have the needs.  Latest....granddaughter needs a bed.  She searches my furniture literature and finds one she likes ($4500 at Moshers).  I build it and she helps.  Don't get any better.  I could go on and on.  Sone in law wanted a chest of drawers with the drawers a specified size.  It is a wonderful thing to be able to build exactly what someone wants.  

I accused you of being a Research person and I have not changed my mind.  There is no greater joy for someone that is driven to research then a satisfying discovery.  You have had many in the few years you have posted here.  Many don't get it.  Overlook them.  

Where can anyone buy a set

"I have used chisels from the 1820s for 45 years." To make this information useful to others two pieces of information need to be added.  If chisels like you have grown accustomed to are to be of any value to others they need to be readily available. Where can 100 people buy a set this year? 

 One has to wonder why the few chisels made in 1820 have not long since worn out if they are so superior to anything made thereafter. 

Second, there is no way of knowing whether your chisels are any better than any other without a well designed experiment to compare.  I suspect Weaver has these data.   David, an answer please.......

People with the skills to make furniture have the skills to determine when one tool performs better than another for how the tool is used. In my hands for my work David has made a superior chisel.  Other's results could differ becasue their work differs.  But I will repeat, beyond a threshold of steel performance, the handle ergonomics trumps further improvements in the steel.  

Re: I'll rise to that bait.....

There was some snark in that. One of the sports of the forums over the years has always been the whole thing of "what's important for me" is "what's important". 

Substitute interesting for important. Sensible, rational, pointless, whatever it may be. 

There's no real practical end to my toolmaking other than the toolmaking - there doesn't need to be, and there's a mismatch at this point for me talking to people who want to debate about it. Somewhere in the archives on this forum, I said I'd never delve into chisel making. I have good enough chisels that it wouldn't make sense. I don't even recall where that went off the rails other than maybe grinding a file and seeing the spark pattern and being really enamored with it. "I'll just make one or two maybe". 

Re: Where can anyone buy a set

the vintage chisels that warren likes are softer. In my opinion, if you can grind and sharpen a ward chisel from 60 years later, they're not as good because the ward is pretty much the same thing, but with more edge strength. The fineness of the steel is the same. 

I think the seaton chest chisels are nifty. I'm going to make four more of that style shortly, but they are not as good at being a chisel as the ward chisel, and the early 1800s butcher chisels and others of the type are very good chisels, but they're not better than mid and late 1800s english chisels.

What the early 1800s chisels do offer is being on the lower end of hardness before a chisel is soft enough to roll, and also having a composition that doesn't hold a wire edge obnoxiously, which is also a good indication of being able to shed very tiny damage instead of allowing it to propagate a foil. 

It is true that anything that I've gotten that's high hardness in the early 1800s or really high hardness in the mid 1800s doesn't perform better. 

You can still find those older chisels on ebay, but you have to know what they look like (marks, etc) to find the really old ones instead of just buying a more recent firmer chisel. it's not uncommon to find early 1800s chisels that would be better if they were harder. 

there's sort of a golden age for everything. 

Chisels - mid to late 1800s. Early 1800s are a softer version of similar quality otherwise.

Laminated wooden plane irons - mid to late 1800s. Early 1800s are a softer version of similar quality otherwise. 

Saws - late 1800s to early 1900s. Saw plates are nicely made before that but hardness is often inconsistent - from a little soft to file-destroying in the same plate isn't uncommon. 

Razors - turn of the 20th century through early mid 1900s (and another good while after that if japanese made western style razors)

Files - early 1900s, especially for really neatly made files. 

when industrial process is figured out to replicate what's being done by hand and do the bulk work quickly without compromise, that always seems to be about the top, and then cost cut follows. 

I'm guessing a little bit on the files because it's not that easy to find unused files. Unlike chisels, files get consumed and the range of acceptable hardness for metal. 

I've had a lot of chisels, files saws and plane irons and am not guessing at any of the above, though. one of the things that sent me down this road long ago was a protracted discussion about how much worse steel was before current steel (it wasn't, especially in steel at the eutectoid limit or a little above or below), and terms like fine grained for a lot of the air hardening alloys (it isn't other than the matrix steels - like 3V and AEB-L - matrix steels always or almost always short carbon a little bit to prevent formation of big carbides with other elements). I had an early 1800s butcher plane iron under the microscope and compared to what an A-2 iron looks like, it looked like it was made of fine clay instead of sand for the A-2 iron. The worn edge was uniform. the same is true for everything through O1 and including water hardening steels that have *a little* bit of tungsten or something else. O1 seems to be the limit for tungsten before grain coarsens and carbides are poorly dispersed (japanese blue has a big problem with this). 

that's more depth than is needed here. 

the bottom line is finding the sweet spot in a steel, matching it to an abrasive and getting it to wear instead of chip or deflect. After that, abrasion resistance can be a fair trade off, or it can be less than fair, and branching out into more steels has a lot to do with what their qualities are in the region where edge strength is good in a tool. 

it is, unfortunately, not that simple to make blanket rules - like more toughness is better, finer grain is better, etc, as O1 is finer grained than 26c3, but it isn't tougher and isn't stronger, and it doesn't hold a fine edge better. Razors are made of similar steel - it's stronger than the finest grain steels and makes a better razor than a lower carbon steel that can't reach teh same strength level. 

The "buy a set part"

In case I may have made finding them sound easier than it really is - to find something like this on ebay, you have to set a saved search for something like butcher chisels or another early sheffield name, an attribute and sit and wait for ebay to feed you what's new each day. 

You end up with a harlequin set of chisels, and not a matched set. there are a lot of very short chisels left from this era, and others that have been setup in a way that's not going to be easy to recover or with very deep pitting. 

To get a sense for my early comment about sandstones, someone has to try something like a later ward that matches well to a very crisp finished edge off of something like a washita vs. an all sandstone or sandstone and slate regimen. the same dynamic exists with japanese chisels - the older chisels and plane irons that were tempered too hard to work with natural finish stones are often poorly prepared or little used. 

I don't do much carving, so I'll yield to carvers on what's better, but addis tools had a reputation for being undertempered. I wouldn't like a gouge that chips too easily, but one that's just a bit on the softer side is quite pleasant, and the same is true for complex moulding irons and H&Rs. there's less to gain there chasing hardness. vs what you can get out of a smoothing plane or more generalized set of chisels. To chase higher hardness, everything has to be right with alloying and carbon, and then the stones need to be able to handle it. 26c3 is super easy to sharpen, but the hardness would make it real trouble for sandstone and slate. India followed by washita and it's biting and general sharpening stays ahead of damage. 

The last comment I think would have a whole lot of historical use just by sense of a user - that a tool has to stay undamaged in general use and whatever damage occurs has to be removed as a matter of routine sharpening. As stones become marginal for a hardness level, staying ahead of typical day to day nits becomes harder. 

this is a matter of speculation based on economics, not ideals. it's the same reasoning about why the double iron eliminated single iron planes for anything where volume of wood planed starts to count and the surface is visible. They are a significant economic advantage. Once a machine planer and/or drum sander gets involved, then, they aren't. In perusing guitar forums, I've seen hand planes mentioned other than violin planes (for carving tops) exactly zero times. 

getting a better result or a good result faster always wins. 

I'll make a guess....

I don't even recall where that went off the rails....  when you detected the opportunity to discover what it took to make a 

superior chisel.  

Re: I'll make a guess....

If I think for a while off and on, it comes back - it's in text on here somewhere with near certainty, but years ago. 

I think I got tired of throwing out old files and asked if they were through hardened. Several people told me with certainty that they were only case hardened and no good for anything else (that's false, though they can be case hardened above their through hardness and probably were surface hardened with marginally hardenable steel long ago). 

I heated one, hammered it and made a thin knife out of it to make a marking knife and then started cutting all of my boxes (for the mandatory recycling required here) with them and they had the same crispness that the chisels do. 

A little knife was a good choice because very thin cross sections of water hardening steel will still near fully harden in vegetable oil. 

I also had a fascination at the time of making edged tools that would have very little burr after a finishing stone but not be chippy, which led to rolling the tips just a little bit on a fine slow to thin a burr as much as possible, which led to other things in combination with making a couple of rosewood plane bodies (which also favored rolling the tip of the edge on a very fine stone  -so much so that a cheap pexto firmer well outperformed a high cost harder chisel that was set up without rolling the edge). 

Walking into curiosities is never really deliberate from the start. 

The little thin knives do help to learn a whole lot about edge crispness, though, and geometry. Cutting boxes with a softer knife is noticeable vs. one that's harder, and cutting boxes with an undertempered overhard knife, same. 

The payoff for much of this stuff that's really not talked about on forums because it's not woodworking is just how many other things are quickly understood without thinking about figuring them out in the first place. Like why razors are a higher carbon plain steel, and why alloying attempts with tungsten didn't work out, and why the stainless razors (friodur) aren't as good and attempts at ultra hard razors also aren't. or pocket knives, or kitchen knives, or plane irons, or on and on.