Judging Temperature by Eye

[D-weaver]

Do you even know "Who is Devin Thomas" ??
this guy giving you "Free advise" has made both "High carbon "what you are talking about" as well as founded the "Stainless Damascus world"
i think he might just have a few years more experience in proper heat treating than most /everyone here combined.. about 30 straight years non stop
Larrin Thomas is his SON..
he is telling you that you MIGHT be able to get a good Heat Treat using eyes/forge... BUT if you want it CONSISTANT use a heat treat oven .. so you don't have to question IF you got the correct temperature or not.. if you insist on working with in consistent temperatures how will you PERFECT your heat treat of any metal ??
but you choose to try to Argue/ Dismiss his advise to you ??
things like this are why "Everyone is a Expert" on youtube .. This is Jo Bob from Beaver Smash Forge i use a Torch to red hot my blade and dunk it in old cow piss .. it makes the best blade in the world..
Knowledge from a "Real Expert" is being given too you out of Kindness/ his desire to HELP YOU.. ignore /don't follow it (as you wish)
Buying/Building a Heat treat Oven is not that big of thing to guarantee a consistent Quality of heat treating.. Is it ??

of course, I know who it is. larrin tested my samples - both the first sets that are steel I've used a lot - both matched book specs and my 26c3 samples bettered larrin's charts. I don't think that's a terminal result, just an indication that more is available in a furnace. And the second sets, which I failed at - spectacularly for 1084.

I asked a question in this thread about forge heat treatment, and I asked another question in another thread about another steel. I make tools, not knives. I didn't ask "what if I get a furnace tomorrow" and I explained what's always been popular in tools vs what I understand about knives. Tools are used in a more controlled way -I don't think I've seen a comment on here that addresses that, but this is a knife forum, so I don't expect it.

Everyone is not an expert - I am not suggesting that anyone not making tools would have interest in what I'm talking about, but when the responses divert to "all roads lead toward ____" (maximum toughness, higher alloying, what's needed if you're selling something etc.) when I ask a simple question that's not related to any of that, it's not helpful. so, why didn't I ask the question on a forum where people make and heat treat tools? There isn't one.

Forums are like clubs - I'm not in the club here. I'm looking to learn something, not join the club. I'll give you an example of what the difference is in tools - someone in a woodworking forum had 3V chisels made based on the suggestion that their toughness would be useful. They're not that great - they were heat treated by BOS. I am a woodworker, and I suggested that the person who made this decision should have heat treated the chisels to 61 based on what I could see about 3V. He replied hat they requested plane irons and chisels be hardened to 61 based on an outside recommendation but due to a mix up in heat treatment, they got 59. I guess this is a typical hardness for knives. I made the same person chisels out of 26c3 - he is a retired research chemist, not a role player type person, who spends most of his retirement making furniture.

My chisels are far better than the 3V chisels because the 3V was addressing the wrong issue, and beyond that, they have abrasion resistance that is completely pointless in woodworking chisels. How do I know my chisels are better? He told me they have a better balance of edge holding and sharpenability than anything he's ever used. I also suggested a modified sharpening method for the 3V to address the lack of hardness and his response was that "I saved them" by making them usable.

I'm not starting from square one here. devin is fascinated with past advice and pointing people toward what he knows about knives., and especially entertained by the fact that I had poor results in 1084 and moderately poor results in 1095. I didn't discount that. Before I move forward, I'm attempting to improve results in 1084 to see what the problem was - something I should have done before ever sending samples - I was lazy. i solved these things with 26c3 (also with trials using file steel) long ago, and then sent samples expecting that they suit my use because of performance in tools, but figuring they would be short somewhere. they weren't.

I get it that the discussions here keep pointing back toward things favorable for knives, but they have no precedent in the world of woodworking tools and probably for a reason. I'm looking to get results in 1084 with this question that are acceptable for woodworking tools, not ideal for knives.

"do you know the eminence" is something that occurs on every forum I've ever been on. I wouldn't even begin to debate larrin or devin on anything about what makes a useful knife. the market is completely unrelated to woodworking tools. The eminence comment isn't derisive - it's a case where there's a couple of people who have usually earned the reputation, but sometimes they are so good at what they do that they will not budge and answer a question that doesn't fit what they prefer. OK, often. So, I have a great deal of respect for devin and appreciate that he's trying to give me the best answer that he can. that he's dismissing my questions entirely after that, I don't really care for, but this is a hobby for me. My hobby isn't to make devin happy - or anyone else. I'm big boy and the comment about likes or not likes (consensus) is very far off from what i'm aiming for in the first place. If it's a consensus only opinion type of place, then so be it, I can move on - which I will do.

It's sort of like walking on to a golf course here and asking someone how to play the course left to right and being told that there's no way to play the course left to right, only right to left and then improving your score while everyone drives by and screams "you a_____e!! play it right to left!!! We're erasing your good scores from the system!!! they were a fluke!!".

Except golf is a lot harder.

 

[Lorien]

'Beaver Smash Forge'

 

[DevinT]

of course, I know who it is. larrin tested my samples - both the first sets that are steel I've used a lot - both matched book specs and my 26c3 samples bettered larrin's charts. I don't think that's a terminal result, just an indication that more is available in a furnace. And the second sets, which I failed at - spectacularly for 1084.

I asked a question in this thread about forge heat treatment, and I asked another question in another thread about another steel. I make tools, not knives. I didn't ask "what if I get a furnace tomorrow" and I explained what's always been popular in tools vs what I understand about knives. Tools are used in a more controlled way -I don't think I've seen a comment on here that addresses that, but this is a knife forum, so I don't expect it.

Everyone is not an expert - I am not suggesting that anyone not making tools would have interest in what I'm talking about, but when the responses divert to "all roads lead toward ____" (maximum toughness, higher alloying, what's needed if you're selling something etc.) when I ask a simple question that's not related to any of that, it's not helpful. so, why didn't I ask the question on a forum where people make and heat treat tools? There isn't one.

Forums are like clubs - I'm not in the club here. I'm looking to learn something, not join the club. I'll give you an example of what the difference is in tools - someone in a woodworking forum had 3V chisels made based on the suggestion that their toughness would be useful. They're not that great - they were heat treated by BOS. I am a woodworker, and I suggested that the person who made this decision should have heat treated the chisels to 61 based on what I could see about 3V. He replied hat they requested plane irons and chisels be hardened to 61 based on an outside recommendation but due to a mix up in heat treatment, they got 59. I guess this is a typical hardness for knives. I made the same person chisels out of 26c3 - he is a retired research chemist, not a role player type person, who spends most of his retirement making furniture.

My chisels are far better than the 3V chisels because the 3V was addressing the wrong issue, and beyond that, they have abrasion resistance that is completely pointless in woodworking chisels. How do I know my chisels are better? He told me they have a better balance of edge holding and sharpenability than anything he's ever used. I also suggested a modified sharpening method for the 3V to address the lack of hardness and his response was that "I saved them" by making them usable.

I'm not starting from square one here. devin is fascinated with past advice and pointing people toward what he knows about knives., and especially entertained by the fact that I had poor results in 1084 and moderately poor results in 1095. I didn't discount that. Before I move forward, I'm attempting to improve results in 1084 to see what the problem was - something I should have done before ever sending samples - I was lazy. i solved these things with 26c3 (also with trials using file steel) long ago, and then sent samples expecting that they suit my use because of performance in tools, but figuring they would be short somewhere. they weren't.

I get it that the discussions here keep pointing back toward things favorable for knives, but they have no precedent in the world of woodworking tools and probably for a reason. I'm looking to get results in 1084 with this question that are acceptable for woodworking tools, not ideal for knives.

"do you know the eminence" is something that occurs on every forum I've ever been on. I wouldn't even begin to debate larrin or devin on anything about what makes a useful knife. the market is completely unrelated to woodworking tools. The eminence comment isn't derisive - it's a case where there's a couple of people who have usually earned the reputation, but sometimes they are so good at what they do that they will not budge and answer a question that doesn't fit what they prefer. OK, often. So, I have a great deal of respect for devin and appreciate that he's trying to give me the best answer that he can. that he's dismissing my questions entirely after that, I don't really care for, but this is a hobby for me. My hobby isn't to make devin happy - or anyone else. I'm big boy and the comment about likes or not likes (consensus) is very far off from what i'm aiming for in the first place. If it's a consensus only opinion type of place, then so be it, I can move on - which I will do.

It's sort of like walking on to a golf course here and asking someone how to play the course left to right and being told that there's no way to play the course left to right, only right to left and then improving your score while everyone drives by and screams "you a_____e!! play it right to left!!! We're erasing your good scores from the system!!! they were a fluke!!".

Except golf is a lot harder.

If knives are so different than wood working tools, why are you looking for information on a knife forum?

Hoss

 

[Bühlmann]

I'm pretty new & I heat treat in a forge. I know that I can get within the margins of a "good" knife with a forge heat treat, but I'm well aware that if I hit that narrow bandwidth of parameters that make a "best" knife for a given steel it will be mostly by accident and not reliably repeatable. That's where an oven comes in, and where I hope that my skills & finances progress enough for that "best" knife heat treat to someday be at my disposal for any given steel.

I've followed this thread & feel like I get it. But I really don't get what the big delta is between wood cutting tools and the knives I make, aside from maybe some edge profiles & geometry. There is a wide range of heat treat characteristics that can be tuned for a given application for any blade, whether it has an ebony handle or is bolted to a cutter head. The chemistry and characteristics of the steel don't care either way.

D D-weaver , you may want to try your questions over at "practicalmachinist". You may get more of what you want to hear over there. Or not. YMMV.

 

[DevinT]

There are two types of cutting, push cut and slice cut.

Tomatoes and other soft materials are cut by slicing. Rope, cardboard, animal hide etc…

Push cut is for chisels, axes, shaving and chopping onions, garlic, celery etc.

Steels with large carbides and higher carbide volumes are typically used for knives used for slice cutting.

Steels with fine carbides and lower levels of carbide volume are used in knives or tools used to push cut. Razors, axes, chisels etc..

Steels with finer carbides take keener more acute edges.

D2, M2, 440c, 154cm, etc.have high carbide volumes and coarse carbides.

O1, 26c3, 52100, AEBL, 1084, 1095, 5160, A2 (mostly), etc, have very fine carbides. 52100 has the smallest carbides and the finest grain of any steel.

CPM/PM steels have medium sized carbides.

Hoss

 

[D-weaver]

Devin hit it - on the cutting. Push and slice exist in the knife world, but everything in woodworking with high hardness steel (as in, not saws) is close to push.

The concept of a coarse edge is a foreign one - there's not really a mechanism where someone working by hand would slice and in the event that it's done with a carving tool, it's done in combination with pushing.

there's also no case where an edge can sustain damage and it's better that it does and it's retained, which is also foreign from knife concepts. if an edge bends or deflects, it's unusable without being resharpened. moving the deflection back into place isn't something done in woodworking as the edge life won't be long.

I've never seen any historical woodworking tool of good quality where toughness was chased in terms of steel, but staying closer to the upper limit of temper is common. whatever the performance is, you have to accommodate it to keep a tough edge from deforming and an undertempered one from chipping out. then it's a matter of whether or not you can live with the tool once you find a point where damage stops.

Same with razors - a high toughness steel would make a poor razor. If someone here has the skill to grind a razor without heating it, I think it would be interesting for them to try to make one out of 52100 and then use it on a regular basis without having to return to the stones. I think the margin between when it wasn't brittle from being almost untempered to having too much toughness would be very slim. Historical razors emphasize edge strength, but the steels have surplus carbon (like 26c3) and aren't the finest grained looking under a micrograph. However, they support a thinner edge and have good behavior with a strop. I have received razors from people to sharpen for them after they've questioned why they weren't good. They're always too soft or not a good choice - even O1 iffy for a razor and when it's tempered where it would be good in a slicing knife, stropping can draw a minute burr. DE blades (the steel) obviously don't resemble something like a silver steel razor that would've been high hardness with surplus carbon and not tolerant of bending.

Plain and simple, razors are superior when they won't deflect at all, but are not hard enough to chip. The edge has to be uniform and very slightly rounded to work properly (cut hair, slide over the skin propped up on the back of a pore. Properly set up, there should be little difference between an edge that's' shaved 200 times and one that's shaved 10.

-------------------------------------------

I have a freshly made 1084 iron - made with 1084 from AKS. to my surprise, it shows carbides in the lattice once some planing is done with it, but more surprisingly, despite being on the high end of hardness for 1084 (slow sharpening on a good quality oilstone), it shows symptoms of being able to deflect an edge and hold on to it rather than letting it go (380F tempered twice for an hour). From a woodworking perspective, I don't know if the toughness is a drawback yet - there is room to adjust the final angle at the edge a little bit.

How does this apply to charpy testing? I don't know. The plane iron is held firmly in place and another iron stabilizing it attaches from above within a couple of hundredths of an inch from the edge in fine use.

if a woodworker has to split or whack at something, they'll usually go for an axe, broad hatchet or drawknife. Chisels are generally used straight into wood (but across the grain) and it's a toxic habit to pry with them or let them flop around when malleting. Different world, I guess.

They (woodworkers) also get cranky with really slow grinding or honing irons since sharpening is already a constant thing.

 

[Larrin]

Toughness is not a measure of how easy steel is to deform. A test showing high toughness doesn’t tell you if it is strong enough to resist deformation; it tells you that it has high toughness. If the steel deformed it had insufficient yield strength for the geometry and task.

 

[D-weaver]

Devin - you may not be happy about it, but I have to thank you. Your criticism got me off of my duff to fix the problem with 1084. I have a steel now that's high hardness and tougher than I want, but I can manipulate that at the end of the sharpening cycle by buffing the apex a little bit to prevent it from deflecting at all.

this is the edge of a worn iron that's planed about 400 feet of cherry. there are no significant defects (this is only 1/100th of an inch), but the worn edge as you can see the angle that's worn - is literally forming a tiny burr as it wears and not letting go of the burr. It is slow sharpening on an india stone and very slow on an oilstone - it must be 61/62 hardness.

Solving this from a practical perspective in woodworking took very little time - wish I'd done it sooner - I didn't have the immediate need and criticism was good motivation. if it seems unsual that I'd guess hardness based on performance on sharpening, I guessed within less than 1 point on the O1 and 26c3 samples that I sent to larrin without ever having had anything tested (but having sharpened other things that were).

 

[D-weaver]

Toughness is not a measure of how easy steel is to deform. A test showing high toughness doesn’t tell you if it is strong enough to resist deformation; it tells you that it has high toughness. If the steel deformed it had insufficient yield strength for the geometry and task.

Thanks, larrin - I'm not doing a good job of communicating that. there are various measures of strength. In woodworking, we want no edge movement, just wear. It has to come from a combination of steel properties, use and edge geometry. The last one is variable, and so is use, I suppose, but nobody wants to baby tools, and nobody can tolerate a fat edge.

I have some trouble equating toughness with a meaningful variable with woodworking tools other than to say when it gets below about 5, it appears that even with high hardness, chipping in normal use becomes a problem. the 10xx samples I sent you showed some small issues even in relatively normal use - I should've heeded the simplest answer to the question about why the edge wasn't holding up - is the grain fine.

I don't observe it in O1, and 26c3 is excellent at resisting edge defects, but 26c3 planes a surprisingly short length of wood before it needs to be resharpened. Probably only 70-75% of O1 (my O1 results don't look like yours, they look like 15-20% more footage than a water hardening steel with almost no alloying - as in not 52100)

Tools that do prying in woodworking generally come in some geometry where toughness isn't an issue (axes, hatchets, etc) - I've enjoyed your writings to some extent trying to figure out why there aren't commercial slicing knives with thinner geometry and a harder temper - I always considered it an ease in making thing and didn't consider that people will return knives that are years old that get broken in prying.

i'm unhappy about the amount of unneeded argument that all of this has caused, but what can you do. The arguing did allow me to learn more, though.

(separate comment - when I sent you the first samples, I think I said something about not being worried about toughness. I'll spare everyone pictures of plane and chisel edges at different toughnesses and hardnesses, but I have them. I was concerned with consistency in hardness with individual samples. I don't know what the hardness variance was in the second set, but they were all junk, so who cares. I looked up the notch test before I sent samples and had trouble visualizing where it's useful for woodworking tools outside of maybe an abuse axe - but I get what it does - it gives a good indication about how easy it will be to break a knife. I have no clue what standardized test provides information about what makes a great straight razor or a chisel - there are things that you can feel that aren't quantified in tests. 26c3 chisels are easier to chisel through wood with than something finer but softer. Wood is an odd cases - it's far more destructive than abrasive cards, but far less destructive than edge denting tests).

 

[D-weaver]

A follow up with the iron - if you don't like this stuff, please put me on ignore (generalized comment to everyone, not a fight starter - hopefully an avoider).

this is the edge at 150x magnification. The height of the entire image is about .019" for scale. This is a freshly made plane iron, so some of the scratches from an india stone remain - they will gradually disappear. Because the first attempt showed what I would call toughness problems (i'm learning -these would be beneficial in a knife) despite the iron being slow to sharpen on a fine india stone and slow to raise much of a burr at all on an arkansas stone, I buffed the apex with 5 micron compound on a buffing wheel both to remove the initial burr and to improve the edge geometry (prevent damage)

After several hundred feet of planing and at double the magnification so that I can see carbides.

The second image edge length is only slightly over 1/100th of an inch. No defects are more than fractions of a 10,000th.

So what value does this have - it means that if this plane planes a piece of wood, the wood will be smooth and reflective with no small lines on it. You can see that a lot of the metal has been worn away by wood, which is why the carbide exposure is easy.

The light flatness at the edge suggests some minor deflection even though significant wear has occurred. I have never seen something like this in a relatively hard iron, but it's small and won't affect anything. The burr was strangely persistent, but not soft.

Additional hardness in a plane iron when it's available adds fine edge life, especially when taking fine shavings.

Fine shavings are also a good test of the quality of an iron - if you can take them until the edge has worn out of crispness and no see them split, the iron will be a good one. The bad samples I sent larrin were not capable of passing this. I've never had any O1 or 26c3 iron that had any trouble with it unless pushing way too far on undertempering.

This is a fine shaving - no splitting. The notch is from a small knot - knots have to be wet to plane nicely and stay in the wood.

I cut a couple of hundred feet of these - no defects in any of the shavings (notice the knot notch on the right).

What a treat. So much different feel on the sharpening stones at high hardness with fine grain.

 

[Pinoy Knife]

A follow up with the iron - if you don't like this stuff, please put me on ignore (generalized comment to everyone, not a fight starter - hopefully an avoider).

this is the edge at 150x magnification. The height of the entire image is about .019" for scale. This is a freshly made plane iron, so some of the scratches from an india stone remain - they will gradually disappear. Because the first attempt showed what I would call toughness problems (i'm learning -these would be beneficial in a knife) despite the iron being slow to sharpen on a fine india stone and slow to raise much of a burr at all on an arkansas stone, I buffed the apex with 5 micron compound on a buffing wheel both to remove the initial burr and to improve the edge geometry (prevent damage)

After several hundred feet of planing and at double the magnification so that I can see carbides.

The second image edge length is only slightly over 1/100th of an inch. No defects are more than fractions of a 10,000th.

So what value does this have - it means that if this plane planes a piece of wood, the wood will be smooth and reflective with no small lines on it. You can see that a lot of the metal has been worn away by wood, which is why the carbide exposure is easy.

The light flatness at the edge suggests some minor deflection even though significant wear has occurred. I have never seen something like this in a relatively hard iron, but it's small and won't affect anything. The burr was strangely persistent, but not soft.

Additional hardness in a plane iron when it's available adds fine edge life, especially when taking fine shavings.

Fine shavings are also a good test of the quality of an iron - if you can take them until the edge has worn out of crispness and no see them split, the iron will be a good one. The bad samples I sent larrin were not capable of passing this. I've never had any O1 or 26c3 iron that had any trouble with it unless pushing way too far on undertempering.

This is a fine shaving - no splitting. The notch is from a small knot - knots have to be wet to plane nicely and stay in the wood.

I cut a couple of hundred feet of these - no defects in any of the shavings (notice the knot notch on the right).

What a treat. So much different feel on the sharpening stones at high hardness with fine grain.

i think part of the "Confusion" is that "Knife Makers" look for the best "Balance" for the intended items to cut . something like this
#1 what types of "Materials" things will i be using the knife/tool for.. Wood/Flesh/Bone. etc
#2 edge geometry this actually maters a lot.. too thin of a cutting edge and it will have little strength to do its job well
#3 what type of "Carbide Matrix" do i want ?? are high alloy or Chromium carbides desirable ?
#4 what are the "Service Requirements" who is getting this "Tool" do they know how to properly maintain it ?? can/will they sharpen it as needed?
i think if you check off a few boxes it makes the decision easier .. a "Wood Chisel that is 1/4 thick needs a longer cutting area than one that is 1/8 thick (edge geometry) to do a decent job
the "Heat Treating is tweaked based off the steel type chosen and the desired performance for its given task.. if you do not have a EXACT recipe how can you re create it ??
i have forged a great number of blades in my years , and heat treated most by "Forge" so i know it works !!! but it does not become repeatable because the steels was "Only brought to temp by color"
and not verified .. same with a Rockwell tester .. without one you are following someone elses info (right or wrong) and can not Verify it as correct..
i don't wish to argue about this type of thing .. so im out after this.. Devin says/Knows a Oven is repeatable and that is proven by the Rockwell tester.. not a guess

 

[Josh1992]

Looks like you got what you needed in the end. I still don’t understand what all the negative comments are from. I think everyone here agreed that consistent and propane forge are not usually used in the same sentence. And the original poster wanted to improve his results not get them perfect. I make knives for fun and use a cheap propane forge to do my heat treats and some blades come out way nicer then some $350 knives I got before I got really into making my own, others broke or warped really bad. It’s just how it goes with those of us who aren’t professional makers. PS it’s cool that we get woodworkers on blade forms sometimes

 

[Lorien]

A follow up with the iron - if you don't like this stuff, please put me on ignore (generalized comment to everyone, not a fight starter - hopefully an avoider).

this is the edge at 150x magnification. The height of the entire image is about .019" for scale. This is a freshly made plane iron, so some of the scratches from an india stone remain - they will gradually disappear. Because the first attempt showed what I would call toughness problems (i'm learning -these would be beneficial in a knife) despite the iron being slow to sharpen on a fine india stone and slow to raise much of a burr at all on an arkansas stone, I buffed the apex with 5 micron compound on a buffing wheel both to remove the initial burr and to improve the edge geometry (prevent damage)

After several hundred feet of planing and at double the magnification so that I can see carbides.

The second image edge length is only slightly over 1/100th of an inch. No defects are more than fractions of a 10,000th.

So what value does this have - it means that if this plane planes a piece of wood, the wood will be smooth and reflective with no small lines on it. You can see that a lot of the metal has been worn away by wood, which is why the carbide exposure is easy.

The light flatness at the edge suggests some minor deflection even though significant wear has occurred. I have never seen something like this in a relatively hard iron, but it's small and won't affect anything. The burr was strangely persistent, but not soft.

Additional hardness in a plane iron when it's available adds fine edge life, especially when taking fine shavings.

Fine shavings are also a good test of the quality of an iron - if you can take them until the edge has worn out of crispness and no see them split, the iron will be a good one. The bad samples I sent larrin were not capable of passing this. I've never had any O1 or 26c3 iron that had any trouble with it unless pushing way too far on undertempering.

This is a fine shaving - no splitting. The notch is from a small knot - knots have to be wet to plane nicely and stay in the wood.

I cut a couple of hundred feet of these - no defects in any of the shavings (notice the knot notch on the right).

What a treat. So much different feel on the sharpening stones at high hardness with fine grain.

love those magnified edges photos

 

[DeadboxHero]

D D-weaver just imagine how good the results would be with a furnace.

 

[D-weaver]

D D-weaver just imagine how good the results would be with a furnace.

they could be even tougher. Which would be bad. I have a feeling that I could make two sets of samples over separate days that would test pretty consistently now, though.

 

[D-weaver]

i think part of the "Confusion" is that "Knife Makers" look for the best "Balance" for the intended items to cut . something like this
#1 what types of "Materials" things will i be using the knife/tool for.. Wood/Flesh/Bone. etc
#2 edge geometry this actually maters a lot.. too thin of a cutting edge and it will have little strength to do its job well
#3 what type of "Carbide Matrix" do i want ?? are high alloy or Chromium carbides desirable ?
#4 what are the "Service Requirements" who is getting this "Tool" do they know how to properly maintain it ?? can/will they sharpen it as needed?
i think if you check off a few boxes it makes the decision easier .. a "Wood Chisel that is 1/4 thick needs a longer cutting area than one that is 1/8 thick (edge geometry) to do a decent job
the "Heat Treating is tweaked based off the steel type chosen and the desired performance for its given task.. if you do not have a EXACT recipe how can you re create it ??
i have forged a great number of blades in my years , and heat treated most by "Forge" so i know it works !!! but it does not become repeatable because the steels was "Only brought to temp by color"
and not verified .. same with a Rockwell tester .. without one you are following someone elses info (right or wrong) and can not Verify it as correct..
i don't wish to argue about this type of thing .. so im out after this.. Devin says/Knows a Oven is repeatable and that is proven by the Rockwell tester.. not a guess

It's not really confusion (it was for me a couple of years ago when someone said "go to the knife people if you want to find something out about woodworking) - I get what the deal is - first step, no broken knives. Especially if you're making them as a pro. In woodworking, you could find beginners who would open a door with a chisel, but one of the reasons that I don't make chisels for anyone other than pros (even then, at no more than cost of materials) is that this is avoided. Anything that bends or pries in woodworking is made for the task.

Second, you will have a huge variation in desired hardness, what kind of edge people want, etc. In woodworking, we don't.

Third, you will have a huge variation in the geometry and type of edge finish that people want to apply. In woodworking, we don't.

here's how a I guess at hardness, but you are exactly right - without test results, I don't know for sure. I only guess at relatively plain steels, but that's what I use. I have sharpening stones that poop out in being able to raise a burr on a plane blade around 60 hardness (sandstones), 62 (washita arkansas) and 64/65 (various natural stones from japan, as well as broken in fine india stones). I can identify relative differences better than nominal actual hardness. This is sort of important in woodworking tools, because arkansas and india stones are commonly used. It also assumes relatively plain steels - add a bunch of carbides and it gets harder to tell anything other than whether or not an alloy is soft to make it sharpenable on stones that it shouldn't be used with. For example, HSS irons were floated out to the market in the early 1900s - I'm waiting to get an XRF done on one to see what it is, but they were tempered a little soft so that they could be sharpen on natural stones. It spoils the potential, but having 75% of the market claim that they couldn't sharpen the irons would, too. Ultimately, those were a failure, much like the attempts at making a razor with tungsten added and much like the friodur razors - which are collectable since they're stainless and they stay pretty, but they're not nearly as good shaving as a good older razor marked as silver steel (whatever that may have been at various times) and tempered harder.

I can't get as good of a feel on knives, though - the contact point varies - plane iron edges never change shape. This method of estimating isn't much different than using hardness testing files, but I don't have those. they're too far apart.

I occasionally browse used C scale testers, but haven't found one cheap enough that isn't broken. If I do, I will buy one.

 

[Cole2525]

they could be even tougher. Which would be bad. I have a feeling that I could make two sets of samples over separate days that would test pretty consistently now, though.

Why would using a furnace to get higher toughness be bad?

 

[Steelhog]

Nobody is answering this thread because this is not the way to get a superior heat treatment.

You will probably argue with me about this. This type of thread comes up every few months and the OP gets frustrated because we just won’t listen or understand what he is saying.

It is impossible to get consistent results using a forge to heat treat. Temperature control is the most important thing in heat treating and you can not get good control with a forge.

I’ve never seen a maker that has a furnace or a salt pot switch and go back to using a forge.

It’s good that you are trying to perfect your heat treating and doing some experiments and testing. Rapid over heating of any alloy is not the way to better heat treating.

If you insist on using a forge, build a barrel forge with a small burner and a small exhaust fitted with a thermocouple. Hang the blade or chisel from the top.

The best thing to do is to sell everything you can and buy a quality furnace. This way you can control your temperatures and learn what you are doing. You can also move to higher alloy steels. You need to try 52100, A2, AEBL, ApexUltra, and maybe maxamet etc…

Lots of good steel out there. Find out which one is best for you.

Makers seem to neglect proper heat treating.

It’s not good to make and sell products that won’t perform as expected.

I’ve seen lots of stuff over my nearly 45 years making knives and poor heat treating is a common problem.

Hoss

Honest question and generally curious but has there been a time, perhaps early in your career or when you first started that you used a forge to HT? Or did you go straight to a temp controlled HT oven?

 

[D-weaver]

Why would using a furnace to get higher toughness be bad?

Long discussion above - too much toughness and how the edge wears in every good woodworking tool I've ever gotten is a poor match. I like what larrin says about high toughness -it allows someone looking for higher hardness but enough toughness to have room to increase hardness further. that's ultimately what we'd do as woodworkers - the moan and groan about some tools being softer than expected is pretty common (they're tough then).

The relatively prevalent use of oilstones does put an upper limit on hardness for some users, though. Around 62 hardness, the stones start to become marginal, which is useful in other ways, but not that well understood.

For woodworking, you're physically pushing the tool into wood all the time. Deflection larger than nicking is actually worse- far worse. If you push an edge to its limit, you want whatever happened to exit the edge and not leave a burr that increases the effective thickness of the edge. No defects are preferred, though and tool design takes away issues that resemble a notch test (bending, side impact, etc). As I mentioned above, the unsupported part of a plane blade is generally hundredths of an inch, and it's restrained above and below.

You can compare the 1084 picture above to 26c3 in this picture. Notice how even the edge wear is after planing a few hundred feet (maybe 400 or 500). this is tempered around the same point as the samples I sent to larrin (those averaged about 63.8 or something). This edge behavior is ideal - no defects in the surface, nothing deflected impeding penetration into wood and resharpening takes about 1 minute because little edge length needs to be removed to have fully fresh steel.

The burr almost comes off without addressing it at all, even at a microscopic level.

In the 1084 picture above, the edge had a much more persistent wire edge, but it doesn't show symptoms of significant deflection, which does occur when you get below 60 or so. The only way to avoid it is to bolster the edge further with change in geometry.

 

[D-weaver]

This discussion of hardness for woodworkers does create a situation where if you run into woodworkers looking for a knife, they're going to want one that will sharpen like a chisel. I've had a small gaggle of older (professional) woodworkers rave about kabar's older knives and talk about how crisply they sharpen but "they're a little soft". Their habits with tools would keep them from doing anything that would break a knife, let's say, that's true 1095 and larrin would test at 8 foot pounds.

(also, the way a plane is designed the wear bevel shown above for 1084 should be curved. On a metallurgical scope of kind of low quality like mine, the light levels tell you what's flat, especially on a lazy attempt like the 1084 picture above where the iron is on the bed of the scope dead flat. To see something at the edge looking back and reflecting light is a little odd - instead of wearing in a rounded smooth pattern, it's as if the point of wear is maintaining a little burr. The dark part of the edge is the rest of that sort of scooped wear. The 26c3 picture is from a year ago or more - the wear bevel could be a different shape due to tool setup, or it could be that I put it on an incline to light the bevel. It is spectacular at holding a crisp edge that wears evenly, though - it just doesn't wear that long.