(Give me the short version, please)
A2 steel would have been a foreign topic to most woodworkers prior to the mid 1990s. The earliest mention I’ve seen of its use is George Wilson mentioning slipping it to coopers at Williamsburg to extend the working interval on their planes. If you haven’t watched a cooper, there’s a lot of white oak planing. I suspect the irons being smithed were not the equivalent of a current W2 or 1095 iron shot out of a quench and tempered back to 62 hardness.
I’ve seen Karl Holtey mention using it early on, as Karl has always introduced something unusual to his planes, or chosen to make unusual older models like the Norris transitionals.
But A2 isn’t really a new steel, and for simple purposes, 1084 steel and some versions of 1095 are about as plain as steel could be. O1 steel as we know it now was introduced with substantial alloying, and especially in regard to alloying that allows it to harden more easily. Water quenches much faster than oil and oil much faster than air. Fast quenches create distortion, or at least can, and won’t through harden very thick items. You’re unlikely to ever see a W2 iron made 1/4″ thick for a boutique plane – it won’t harden properly. O1 will easily.
Given that background, A2 is a steel with molybdenum added, significant increase in chromium (to 5%) and with a small amount of vanadium…..and a lot of manganese. O1 also has a lot of manganese, but only a little bit of chromium. Consequently, A2 can be air or plate hardened (placed between two cold aluminum plates). The result is a steel that tempers to about the same hardness as you’d find in O1 – good O1 probably lands between 61 and 63 hardness for woodworking. Good A2 will land around the same place.
What is air hardening? A2 will definitely harden if you hold it up in the air after heating it, but air hardening is generally prescribed in a pressurized furnace. Why? If you increase the density of air under pressure, it has more ability to transfer heat and it will cool A2 faster. I don’t know for sure, but would guess the bulk of A2 now is heat treated in furnaces in a vacuum under several multiples.
So, basically, what are the trade offs? We get a steel that is very easy for manufacturers to use because it can be quenched relatively slowly, and on top of that, it’s very insensitive to tempering temperatures, unlike higher carbon steels. The difference in hardness for a 100F tempering error is about 1 point. That’s the benefit for the manufacturer, it doesn’t do much for us as users other than make availability simple. It’s also not particularly expensive. What users do get is a steel that has chromium carbides that impart additional wear resistance. In wood in actual tests planing wood, I see a potential at same hardness for 25% more edge life.
The trade off is the chromium carbides are relatively poorly dispersed compared to the much smaller carbides in O1, and they provide more sharpening resistance than they return in edge life, and in poor quality samples, carbides can seed small nicking. If you experience problems with nicking edges in A2, the universal fix in tool and knife steels is to add a couple of degrees to the angle. If you have chipping with an LN iron, for example, just sharpen the final microbevel at 35 degrees. What little you lose in clearance, you’ll more than save in predictability.
That pretty much covers what the steel is – it’s around 1% carbon just like O1 and W2 – with the latter often being more in the 0.9-0.95% range. Not sure about the former, but chromium does tie up iron in carbides, so it would make sense that there is a bit more carbon in A2 to leave a similar amount in the martensite matrix (the part of the steel that we would see as “grains”).
From a practical standpoint, it does seem to be offered in a much narrower hardness range than O1, and I think many who prefer A2 over O1 probably aren’t planing much and may have experience with two things: 1) underhardened O1, and 2) a lot of steels they think are O1 that aren’t anything close.
Vintage plane irons that are laminated aren’t O1, they are something finer with less alloying.
I don’t know too many experienced woodworkers who use hand tools a lot more than just as a follow on to power tools who like to work with A2. There are certainly plenty of amateurs who like it just fine, and if you like it, certainly keep using it.
So, let’s address some things I’ve heard about A2 in some mock back and forth questions.
A2 is OK, but V11 is a much finer steel – it’s powder metal
This statement is false. V11 (XHP) is a higher volume of chromium carbides and the carbides are more uniform, but the larger carbides are similar to the carbides in micrographs of A2. The powder metal comment for V11 is true – look up “CTS-XHP micrograph” if you want to see what it looks like.
A2 is fairly new. They’d have used it in the past for tools if they had it. We have better steel now than they did.
Depends on what you mean. A2 has been around in some form since the 1920s, and probably little different from what we have now since around 1935. It was developed around the same time as D2, which itself was an attempt to make a less expensive high speed steel. But D2 didn’t and doesn’t hold up at high speed. It’s to A2 what A2 is to O1, and V11/XHP is somewhat like D2 with more chromium and carbon and because it would be so coarse in ingot form, it’s made with a powder process. D2 is also.
However, as long as A2 was used industrially (could very well have been used at Stanley!) for dies, it wasn’t really wanted for woodworking until amateurs came along. It’s likely for Lie Nielsen that it replaced a W series steel because Lie Nielsen couldn’t tolerate warping. And the popularity for a while of the A2 and D2 types of steels in knives may have gotten them exposure as blade steels.
But, no, woodworkers didn’t have to suffer without it from the 1920s on, they just didn’t have any interest in it. The amateur market was probably small as the push in the US was for modernity.
A2 steel is really tough
We don’t really test steel hardness, but A2 isn’t exceptionally tough. 80crv2 and 1084 steels that have very small carbides (and AEB-L on the stainless side, and 3V in powder metals) are really tough. Tough means they are hard to break. Not hard to bend, but take a lot of energy to break.
This is said about V11, too, but V11 is also not particularly tough. What A2 and V11 have is the potential to have edge strength with hardness (just like W2, and 1095, and so on). We don’t use S7 and other very tough steels that don’t have good hardness potential. And we don’t see 1095 in blades, though made in good quality, it would make a perfectly serviceable plane iron. It’s too difficult for boutique toolmakers to heat treat accurately.
Cryo treated A2 is better yet, it’s even tougher!
In my opinion, cryogenic (just resting the steel in liquid nitrogen after quench and before temper usually) does improve A2, and most anything we use for woodworking. But it actually makes A2 less tough. It converts remaining unconverted microstructure to martensite better than stopping at a higher temperature. Martensite is hard. The unconverted austenite from heating prior to quenching is not hard, but it’s tough. More martensite, less austenite, and the steel gets harder but more brittle in a break test. How much harder? Generally about a point on the rockwell scale. It does make the steel look slightly different in a micrograph (carbides look smaller, everything looks more dense), but the gain is general gain is in hardness.
Since we typically don’t test the toughness of steels in woodworking (that’s for crowbars), the extra hardness is nice and the loss of toughness is fairly small.
But there’s another benefit to cryo treatment – steels like A2 can begin to suffer when overheated because so much austenite is created at additional heat that much is left unconverted. Liquid nitrogen will convert much of that, creating a much wider acceptable range of heats and even the ability to chase hardness a little bit by creating what would’ve been softer steel due to excess austenite, and convert that to what we know as hardened tool steel – more martensite. Nice trick – too bad liquid nitrogen doesn’t come from a faucet. I’d love to have it on hand!
I do not personally see a reason for it to not be cryo treated and wouldn’t buy A2 that isn’t. So, better? yes in my opinion. Tougher? No. More wear resistance/longer edge life? Only to the extent that the steel is a point harder.
A2 Steel doesn’t get as sharp as other carbon steel
This depends on the sharpening media. But the statements made like that often consider O1 to be “carbon steel” even though it’s fairly highly alloyed to make the oil hardening possible. It can be true that dispersed carbides 5-10 microns in size can end up in the edge of an A2 iron, crack and fall out leaving behind a nick big enough to leave lines that can be felt on wood. But this statement is more commonly made by people who are not completing the sharpening process on A2 (it takes longer than O1), or using oilstones or something else that won’t cut carbides.
Diamonds and other oxides and waterstones will create an edge that is no different as long as any burr is dealt with. That is, it’ll be a little more work to get the fine edge, but there will be no perceptible difference in sharpness.
If I were still using A2 a lot, I would probably just cut a secondary bevel on a fast stone and then use micron diamonds to finish it. Why screw around. A better result than something like shapton glasstones or whatever else is being sold as the upper expense level fine stones, faster and for almost no cost. I’d do the same for V11/XHP.
If you like to use natural oilstones, there’s just no reason to use A2 with it. You won’t get a return for your efforts. And for some reason, the lovely washita stone and A2 don’t get along at all. I don’t have a picture, but I could probably create one (thought at one point I no longer had A2, but I do have lie nielsen’s spokeshave irons). The washita does something to break or tug at the carbides and leave a coarse edge. Under the microscope, the effect is seen easily.
Diamonds, on the other hand, don’t notice any carbide in common steels – not even vanadium. Vanadium provides a little more resistance, but the groove left in steel shows no favoritism – diamond leaves a wake like a plow through soft dirt.
Probably Chosen by Toolmakers, not for Woodworkers
This is my statement, not a question. Why do toolmakers like it vs. the narrative that it was “given to us because it’s better with a longer lasting edge”.
- O1 is now seen by toolmakers as a steel that warps a lot. Hock’s irons out of France are tempered hard and it doesn’t seem to be an issue, but it’s a challenge to find high hardness O1 that I’m aware of other than Hock and in Iles chisels.
- A2 heated to a proper temperature will land around 61/62 hardness after a 400F degree double temper. If the temper is 500F, an error nobody would ever make, it would drop a point in hardness. O1 would drop 3, which would drastically change the usefulness of an edge.
- A2 steel is relatively inexpensive, and widely available
- A2 when air quenched moves very little, leaving less follow-up grinding and clean up. The lack of movement makes it very easy to find heat treatment, and the heat treatment routine is uncomplicated (it should be done in an inert environment, though, but in a computerized furnace, this isn’t an issue)
- Compared to other steels that have very coarse structures, A2 is coarse compared to O1, but fine compared to D2.
- A2’s carbides are chromium, which means any synthetic sharpening media will sharpen them fine. The carbides are significantly harder than natural oilstones and they can be used to sharpen it, but the carbides will not be cut. They will rather be burnished and broken to fall out as you’re sharpening. Bottom line, most people use synthetic stones and won’t be offended sharpening it like oilstone users will.
If something is easier for manufacturers, they will use it. Fortunately, for us, it’s still usable. For someone using a power grinder and a honing guide and synthetic abrasives and having to grind a bevel once every two months, you probably won’t care.
Composition wise – I usually provide the actual listed composition, but in this case, I think mentioning it’s bits and pieces vs. O1 is useful.
Carbon – both about the same, but sometimes .05-0.1% more carbon in A2
Chromium – 10 times more in A2 (5% typically)
Manganese (for hardenability) – about the same. Chromium and molybdenum work beyond just manganese in making the steel harden without fast quenching.
Vanadium – a small amount in A2. Sometimes in O1, sometimes not. The function is to prevent grain growth during heating, which can allow pushing for slightly higher heating and resulting hardness without growing grain.
Molybdenum – none in O1 – as mentioned, A2 has 1% or a little bit more. Larrin mentions that Molybdenum is generally a good way to increase hardness in steels with 3% chromium or more, so it makes sense in A2, D2 and high speed steels.
O1 has a little bit of tungsten, silicon and nickel. A2 has about the same silicon and nickel, but no tungsten.
I think unless you start to gather what composition does, maybe this stuff isn’t that important.
Micrographs
I refer back to some steel supplier’s pages, and have learned a lot from Larrin Thomas’s page.
I mentioned to Larrin how excellent the micrographs were – they are not easy to create and are generally done with contrasting techniques to highlight carbides and an SEM. I won’t be making them. Used SEMs aren’t always that expensive, but having something that I absolutely have no chance to fix is not on the menu. Larrin gave me permission to link to his micrograph images as long as I give him credit and provide a link back to his site. I will *gladly* do that.
I have linked O1, A2 and V11 below, as well as links to the micrograph page in general. I chose these two, because there are probably a few people who think these three encompass all woodworking steels, whereas I doubt any were common 75 years ago (only A2 and O1 existed at that point of the three).
On to the pictures – credited to Knife Steel Nerds, of course. The little light dots are carbides. They are seated between steel grains. You can’t see the grain lines in these micrographs because they need to be etched with an acid to appear, but they are there, and generally the borders show grains larger than carbides. How do we explain this? Imagine a stone patio made with brick-size stones in non-identical shapes and marbles to golf balls filling up little spots at edges and corners.
O1 micrograph:
A2:
Notice the disparate carbides here, lots of small ones – some 5-10 microns. D2 steel is made in powder metallurgy version with the chromium well dispersed, and there may be PM A2, but it would be hard to make the case if you’re going to the expense that it would worthwhile vs. D2. D2 in ingot form is pretty terrible – carbides disparate much longer than these leading to edge sections of several thousandths that could break out and worsen. it has a reputation from pre-PM days of being a “steel that can take a terrible edge and then hold it for a long time”. To my knowledge, the Iles tools made in D2 are powder metallurgy – just in case you have those mortise chisels and don’t remember any ragged notchy edges off the stone. That confused me, too. D2 and powder D2, similar composition, very different result.
And CTS-XHP (PM V11)
You can see in XHP, the larger gloms of carbides are less like big ones, but connected small ones. It’s more uniform than A2, but not really finer and the toughness is less.
For reference, the 20 micron scale is just below a thousandth of an inch. what happens when a crack or nick forms due to carbides in the edge is that the carbide cracks and leaves the matrix leaving behind a ragged hole. If the steel has significant carbide volume or uniformity issues, the adjacent steel will also break loose, so a point that breaks out wears to a wider, but not much deeper defect. A fine steel with good stability will not widen much in the scenario that something like silica makes the notch instead. Translation, when carbides come out, the nicking will probably end up being bigger than the carbide void, propagating laterally in some cases because loss of lateral support for the remaining steel.
Check out the whole page at knife steel nerds if you want to review pictures further. I think Larrin is one of the few folks on the internet who provides so much information that he’s worth donating a few bucks to. He is starting to formulate alloys that are actually legitimately new, but he could do that without having done so much providing of information that really doesn’t benefit him.
His excellent page on A2 is here. Knife use with it was more common in the past – the market for knives definitely progresses faster and is more exploratory if not always providing new alternatives that are practical.
Of Making by Hand with Wood and Steel 
First, thanks for the blog. I, too, tend toward verbosity and detail—particularly technical detail, and therefore appreciate your posts.
I haven’t commented previously, but the following statement prompted me to do so.
“If you increase the density of air under pressure, it has more ability to transfer heat and it will cool A2 faster.”
This statement is not consistent with the physics. I’m happy to provide more details, but a brief summary is below.
1) The thermal conductivity of a gas is approximately independent of pressure when the mean free path of the particles is significantly shorter than the distance between the object being cooled and the nearest “cold” object. At 1 atmosphere of pressure, the mean free path for air is roughly 0.1 microns. This is quite possibly less than the surface roughness of the A2 parts, let alone any out-of-flatness or surface profile mismatch between the A2 steel and the aluminum plates you reference.
2) The mass flow rate in forced convection is the dominant determining factor in cooling rate rather than than the gas density (pressure). Any gas has some kind of specific heat capacity (temperature rise per unit heat energy per unit mass), so all else being equal the mass flow rate dominates. At faster velocities and lower viscosity (lower pressure for a given mass flow rate through a given furnace) the “boundary layer” between the bulk gas flow and the object being cooled will be thinner, which will increase heat flow as well.
3) Given a fixed-size inlet and outlet for the furnace, increased mass flow rates will of necessity increase the pressure inside the furnace—there has to be some kind of driving force to generate mass flow, and for any fluid the driving force is all about pressure gradients. Thus, increased pressure may well be simply a byproduct of faster cooling rather than the driver thereof per se.
4) Pressure does also change the average rate of collisions between gas particles and surfaces, so perhaps an increase in pressure may also be aimed at a surface interaction between the steel and “quenching gas” rather than having anything to do with cooling rate or being solely a byproduct of increased mass flow rate. This last is a guess, while the rest is easily verified.
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(this may be a good time to ask chatgpt something for the first time as google provides a response that there are five main hardening processes)
Server hardening.
Software application hardening.
Operating system hardening.
Database hardening.
Network hardening.
(I don’t think those are ovens!)
I also didn’t consider some of the other factors enough – such as the desire to really knock the pennies out of the process with vacuum furnaces – to have a bright part even after heat treatment. that seems really lazy, but in quantity, it would be really useful,
the first hit that google provided for vacuum heat treatment is that it “results in higher hardness”.
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Do I appropriately interpret your response as interest in sources to back up my comments?
For 1), you can Google the phrase “thermal conductivity of gas versus pressure” and quickly find numerous sources agreeing with my statement.
For 2), any reasonable thermodynamics text should provide the following expression: Q = d/dt m *Cp*dT where Q is heat flow rate, d/dt m is mass flow rate, Cp is the specific heat capacity at constant pressure (close enough for forced convection in a quasi-steady-state condition), and dT is the change in temperature of the gas at the inlet versus the outlet of the oven.
For 3), any reasonable fluid dynamics text should show that the mass flow rate in the turbulent flow regime (where the flow is “fast” as defined by surface roughness and what is known as the Reynolds number and/or the Nusselt number in the case of gas-based heat transfer out of a solid medium) is proportional to the pressure gradient driving the gas flow. A few more details: in the “boundary layer” between the low-velocity gas near the surface (zero velocity at the surface) and the bulk gas flow, the heat transfer is a combination of conduction and convection. The characteristic thickness of the boundary layer (and therefore the Nusselt number for any given gas) is a function of the gas viscosity (temperature and pressure) and bulk flow velocity as well as the geometry of the part over which the gas is flowing and the direction of the gas flow across the part. This in no way undermines the accuracy of 2): the total heat flow out of the oven is still easy to calculate if one knows the temperature rise of the gas, its specific heat capacity, and its mass flow rate. One can then easily calculate the bulk average cooling rate based on the total heat capacity of the oven and its contents.
For 4), the kinetic theory of gases tells us that the collision rate between gas particles and a surface is proportional to (number density–how many particles per unit volume) times (average velocity of any given particle). Both number density and average velocity are functions of pressure and temperature. Any speculation on my part about desirable/undesirable interaction with surfaces in the context of A2 steel is only that–speculation.
My knowledge of heat treating is very limited. From what little I do know, with regards to the comment Google provided about vacuum heat treatment resulting in higher hardness (higher than what?) I’d expect that the surface hardness of heat-treated high-carbon steels would be lower in an oxidizing atmosphere than in vacuum due to “burning off” the carbon, but it seems likely that heat treating in an inert gas would accomplish the same thing. Conversely, an appropriate carbon-rich heat treating environment can surface-harden steels by increasing the solution carbon content (diffusing carbon into the steel), which can result in higher surface hardness than vacuum heat treatment. From what little I know, it seems likely that any such statements must include appropriate context to be meaningful.
The removal or addition of carbon (or oxygen, nitrogen, hydrogen, . . .) are surface-driven and diffusion-based effects; these are therefore based on concentration gradient, diffusivity at temperature, and time. In all cases one can in principle remove enough material from the surface to move past the surface effects into the bulk material which wasn’t exposed to the heat treating atmosphere to begin with.
This all assumes that the cooling rate can be sufficient for appropriate quenching of whatever material given any particular heat treating environment and set of equipment.
While the following is also speculation, the brightness of a part after heat treatment may be a primary or secondary effect (or both); a relative lack of decarburization at the surface may result in fewer customer returns for chisels and plane blades, because the initial edge-holding properties may be closer to the longer-term behavior. It seems like double benefit: less post-processing and fewer returns from customers. Again, just a guess.
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Second comment – I’d forgotten this, and probably not relative to A2, but XHP, which I have heat treated with the quick and dirty method. The issue is as follows – with oil or air hardening steels, the phase below pearlite where steel changes from austenite to martensite (so get past the pearlite phase quickly and get to a temperature where martensite forms, and then we temper that) is below a temperature that someone like me would quench.
Translation, get past pearlite quick (soft structure that doesn’t harden), and then the lower limit of the temp range for a quench to be is safe because we’ll never hit it. It could be something like -150F. I’d have to look it up. My freezer will give me a pot of propylene glycol cooled to about -35F at best.
This isn’t always the case for air hardening and high speed steels – the lower limit being a safe range. I believe the terms on schedules used for it are “martensite start, and martensite finish” range. if you’re above that, you get bainite probably (not totally sure) like you see in narex’s lower range of chisels. this would be fine, too, except bainite structure steels don’t get enough hardness to be anything but mediocre.
Back to XHP – i’ve hardened it in oil thinking I could chase better hardness. it turns out from the heat treatment schedule that hardness is actually a little better in still air, and then the instructions go further to state that 50F per minute from austenitizing temperature is needed for optimum heat treat response.
this is boggling. I am probably chasing from 1700F in a quick heat to 800F in two seconds, and then switching from quench oil to something even faster to get to the martensite formation phase. In short, I want to change temperature as fast as possible to get into martensite making out of whatever austenite is there. The temperature sounds odd, but I am working with a faster heat so some overshot is necessary vs. electric furnace schedules that can relax and get things into solution slowly.
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No, I don’t doubt what you mention at all. I assumed that the increase in atmospheres was some way related to soaking more heat out of the steel, because it’s common in the knife world to increase air flow to increase hardness when plate hardening.
Not everyone is wired like us, though, so the guys who mention a pet method don’t really say “i get X hardness with compressed air and Y without”.
Taking what you say as correct (i’m not one to really question people who know more about something than i do, especially if it will point me in the right direction if I can find more information about the vacuum and multi atmosphere heat treatment methods), it becomes a question then of what’s the need for multiple atmospheres as compressed methods show up in some Q&As as both being running compressed air over samples and having a machine that moves the air itself.
and the curious add on is the vacuum systems resulting in improved hardness over still air – there are a lot of reasons that could be. It may be thermal transfer, or it may be some other reason.
I just don’t know. From a physics perspective, it will also matter if we’re talking about still air (truly still) or air that is flowing on purpose.
I watched a video of a peters apparatus that heats steel and then moves it to a compressed chamber. They said something about not necessarily using it that often for hardening at this point, but it was boggling because the heated steel was in no hurry to be moved from one chamber to another. the whole air hardening thing and no scale and slow quench is a different world for me. I’m panicking if I can’t get the steel in the quench in half a second, and scale isn’t on my mind at all.
Does it really matter that we figure this out? I guess for hobby folks, maybe not, but it’s interesting because the steel and how it’s heat treated are two things that go together. The message we get about air hardening steels is generally that “they’re more modern and better”. But as far as I know, few boutique makers using air hardening steel do their own heat treatment, so there is probably a significant business reason, or could be, to use A2. I remember LN or someone who spoke on their behalf saying that the steel is more expensive (A2), which may or may not be true depending on the source of A2 and O1, but no discussion was had of the aversion now to have any labor or skill involved in correcting things like movement, or discarding scrap. I would imagine A2 is at best cost neutral with the treat on the back end that everyone likes to heat treat it, and some hardening services now are declining to do even O1 let alone water hardening steels. And you pretty much can count irons before and irons after and have the same number with very little follow up grinding.
I’d be surprised if the LN and LV companies have much involvement other than maybe preferring a hardness target, as they don’t use accurate terminology sometimes about steel. For example, referring to cryo treatment as making for very tough steel (it reduces toughness, but increases hardness).
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“Not everyone is wired like us. . .” Indeed–at my workplace, there is an expression based on my name for an email that is long, detailed, and contains enough information that it may prompt a follow-on meeting for further discussion. Fortunately for me, I work mostly with people who appreciate the level of detail and enjoy learning more–and I, too, enjoy learning as much as I can from them. I’m well aware that I’m an outlier, particularly in the context of woodworking in general let alone working almost exclusively with hand tools.
Increasing air flow is definitely a way to increase the cooling rate–multiple atmospheres inside the oven, assuming a gas outlet from the oven, will definitely increase the cooling rate compared to near-atmosphere cooling in the same oven simply based on the increased mass flow rate.
There is a potential advantage for compressed air versus machine-moved air: specifically, the cooling effect of decompression, which will in turn increase the cooling rate for the parts being cooled. When any gas goes from high pressure to low pressure, its temperature will drop, which then gives “more room” for the heat to flow into the gas, increasing the cooling rate compared to the same mass flow for solely-machine-driven air flow. From inlet to outlet of an oven, it’s all about mass flow rate, temperature rise, and specific heat capacity (as a function of temperature, by the way).
Heat transfer in vacuum is going to be slower than heat transfer in air: in vacuum, heat transfer mechanisms include conduction through solid materials and thermal radiation. In gas, one has these along with convection and conduction through the gas. Under otherwise identical conditions, then, cooling in a flowing gas will always be faster than cooling in vacuum.
“Still air” in the context of heat transfer is solely a theoretical construct rather than an achievable physical reality: as soon as you have any heat transfer to the air, you generate motion of the air (it expands–decreases in density–as it heats, which drives buoyancy and therefore motion), which in turn drives convection. Forced (driven) convection pushes the heat transfer rates higher.
“Better” for any steel versus another also requires context: better for whom and in what way? It can (for example) simply mean more convenient/less costly overall for the manufacturer rather than having anything to do with the end-user. I don’t know anything about the cost of various steel alloys for tool making–materials, heat treatment costs, or otherwise; the components I design for work have never been built of any of these materials and so I have never had cause to examine the cost in a production or prototype environment.
With regards to A2, it’s definitely not my preference for planes and spokeshaves (I have the LN Boggs flat and round bottom spokeshaves)–never tried it in a chisel–while simpler high-carbon steel is my preference in both plane irons and chisels. Thanks to my great grandfather’s hand-cranked grinder, I don’t have a problem with my LN A2 plane irons as long as I keep them hollow ground to effectively mimic sharpening a thin iron, only use them for relatively light work such as jointing–after the try plane–and finishing, and as long as I use appropriate sharpening media (I still have trouble sharpening A2 on Arkansas stones, while old Stanley irons–whatever the steel is–do very well on them). Maybe once I improve my skills with my great (and great-great) grandfathers’ planes I’ll sideline the LN planes, but that’s not happening in the near future–each has its useful place in my shop at the moment. For finishing work, sharpened and polished A2 is effective for me; for bulk work, I definitely prefer the Stanley and “Rev-o-Noc” irons that came with my inherited planes.
Does it matter if we figure this out? I don’t think it matters per se, nor do I expect we have enough information immediately at hand to fully understand it. Regardless, I’m the type of person who likes to indulge curiosity for the sake of satisfying my curiosity. I’m interested in (among many other things) the relationship between steel chemistry, heat treatment, manufacturing method, etc and how these relate to desirable/undesirable properties for tools of various sorts. Does it help me be a better woodworker? No, but I still enjoy the learning.
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There’s a key comment in the end of that. I agree with the rest, though as I’ve gotten older, I “turn it off” at work if the audience won’t do anything with it and unlike here, I have no issue with writing an executive summary that tells a client the objective, a few summary details and the conclusion they should find (and their responsibility or pointing to their responsibility).
But the end part that’s key – it is your pleasure and satisfaction to think about it, not to cede thinking about it. I still make mistakes all the time. I just checked an iron that I thought would be 61.5 and it’s 60. Sometimes I think I’m past that, but it happens. Thankfully, our mistakes get smaller with proficiency and the iron in question here is below my cutoff for feel, but it would be good in a jack plane.
it is my pleasure to do this stuff and to feel and see and hear it. Does it make me a better toolmaker? I guess that depends on what toolmaker means – does it mean I make X number of units to spec and cede some things to others? that wouldn’t be my pleasure. but solving the problems of getting the result and then trying to get it every time without removing us from the equation is.
A2 steel is fine, of course – I don’t prefer it, but as long as there isn’t a stray carbide in an edge that’s finish planing and the iron in question is plenty hard, it works well.
As far as atmospheric stuff, I had incidental contact with physics in high school (not required for a math major in college), and meteorology, too. When it gets more complicated than the adiabatic rate (wet or dry), pervnert or what causes lift on the top of an air plane wing, I can get lost and the only way I could get an accurate answer is to set up an experiment and observe outcomes.
I know if I set up an alt and went to bladeforums and started asking people who use different quench methods if they tested various results, people would get cranky! today is actually a learning experience for me – by quenching XHP (V11) in oil and then following up with the freezer, I’m not actually getting better (not even harder) results – they’re about the same. I could just as well leave the iron sit in still air.
And a nod to what that means – given the recognition of what you say from a meteo class perspective – as soon as you start heating one mass of air and not others, it’s not going to be still.
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Fortunately, at work I have (mostly) an audience that will do something with what I generate. Hooray for a bunch of research and development engineers and physicists! That said, I tend to start with an overall summary–a “TLDR” version–and then launch into the detailed version for those who prefer such.
I for one have had much more than incidental contact with physics and engineering; I have formal (University) training in mechanical engineering, electrical engineering, and physics as well as a great deal of on-the-job learning in each. Anyone truly skilled at such things will tell you: the university stuff gives you a foundation to learn how to do your job–the rest is up to you.
I do not doubt your assertion regarding the likelihood of people getting cranky about questioning their methods as compared to alternatives. I’ve witnessed such responses to a number of your posts, just as one example of such behavior.
Specifically with regards to woodworking, I enjoy development of my skill for the sake of observing my progress in developing my skill. For example, I’ll make a workshop shelf extension with an unnecessary number of dovetails simply to get more practice with my sawing and chiseling skills. I purchase rough-sawn wood and use it for my projects in large part to improve my skills with planes (I don’t own let alone use power tools for processing rough lumber). I enjoy making things that I or others will enjoy seeing and/or using. I enjoy experimenting with tools and techniques and observing the results (and then making changes based on those observations, observing the effects of the changes, . . .). I enjoy diving deep into how things work and why they work the way they do–and how to make them work better, should the opportunity arise. I enjoy learning from those much more experienced and knowledgeable than myself–and reviewing what they said at a later date to understand more about what they meant with their advice.
With regards to the lift provided by an airplane wing, there is a relatively simple and correct perspective–and one I’ve never seen taught in a university class, for reasons I can only attribute to lack of intuitive understanding on the part of the professors involved. Specifically, it’s all about momentum transfer. Deflect the air downward using an airplane wing, and you get a force upward on the wing that’s equal to the time rate of change of momentum of the air. Ignoring any considerations of aerodynamics or considerations of continuum flow of the air and so on, that’s all there is to it. In my experience, they like to talk about static and dynamic pressures from the air acting on the wing, how this depends on the speed of the air under versus over the wing, and on and on, but in the end lift always comes down to momentum transfer and nothing else: deflect the air downward, get a force upward.
Clearly, we’re straying way off topic here in some regards, but I for one am enjoying the discussion. It’s your blog, so I’m happy continuing the discussion while you’re willing.
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No problem on the discussion. There are no rules here written for sure. the only one I’d have even if it was written is that the discussions can’t be dishonest, misleading or with no intent to benefit anyone.
your point about wings explains (if i’m following) the reason some of the early airplanes didn’t have modern design, but ended up encouraging the top air on the wing to end up lower after the airplane went by.
I just watched a video of an airfoil with smoke lines. It shows what you mention – the air is lower behind the wing than it was in the front.
I never studied airfoils but would guess the concave early wings created a lot of resistance to the air going under the wing (slowing it down) and thus drag.
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It sounds like you have it correct; lift is all about momentum transfer, but drag is an important consideration for a practical airplane wing–in general, a combination of drag and lift properties is optimized for different portions of the flight and at different speeds. Simple idea, vastly complicated execution and optimization–far beyond my present understanding of aerodynamics (though I’m interested in learning and at least naive enough to believe I have a sufficient foundation to do so, should the opportunity arise).
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Side note: drag is all about momentum transfer, too. Deflect the air forward, get a force backward.
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exactly what I gathered from the video. Though it didn’t make the same point you did, I think it did indirectly, which is the aerodynamicists frustration with the simplified explanation about the velocity of air over a wing. It ignored the fact that the shape of the wing made it so that the air was “bunching up” under the wing and the air at the back was proceeding over the back of the wing to the end before the air at the bottom got there, despite having a shorter distance to travel.
the trails of smoke made it more clear the simple fact that the air at the back was not only arriving earlier from the top but if you tracked lines horizontally, the air on the low side was compressed to some extent, creating some drag and as you say, certainly imparting a force. the result was that the air traveling over the top ended up lower (vertically) after it made its trip. if it’s going down, the plane goes up.
separate, on the pressure side. Last week in western PA, we had very strong winds – saturday, I think. I was on the couch waiting for the kids and the front door was unlatched. Each time we had a gust, the front screen door (window, no screen) would pop open just a little and then shut. The kids were puzzled. I didn’t look at wind speed but the NWS showed a maximum gust of 64. thankfully, no leaves on trees. it was a fun little study in air pressures in and out of the house. the kids weren’t interested.
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Yeah, there’s interesting stuff to be learned about physics in all sorts of everyday experience as long as one is willing to observe, experiment, and ponder–including in working by hand in wood and metal.
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