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PumpIron
40
Aug 29, 2018
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61 HRC is pretty good for a kitchen knife, but why the loss of 2 pts from 63 during grinding? That implies they're ground hot and fast instead of wet, which typically results in varied and unpredictable performance.
Aug 29, 2018
Deaomega1214
478
Apogee Culinary Designs
Aug 30, 2018
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PumpIronWhen you heat treat a blank of steel, it is a lot like baking bread or tempering glass. The outer part of the blanc is exposed directly to the heat treat and quenching. This is like the crust forming on bread. It is harder than the inner part of the loaf. So when you grind into the blanc the inner part, will be slightly softer at the edge than the spine. If you notice, the Germans give a range in their literature, because if you HRC an finished knife it will always give you a different number depending on where you test it. The Japanese give you a straight number, because the blanc heat treat is the only number that is ever consistsnt. I also must respectfully disagree with your assessment of the reverse scallop Edge. As the designer of this knife and also someone who has been in manufacturing for 30 years. The reverse scallop edge lasts way longer than a standard serration. It also cuts way cleaner. I would like to also point out that this knife is not a bread knife. It is a super slicer that will cut bread and cakes with minimal crumbs, and will also slice meat and fish. Again the reverse scallop edge will not tear. The purpose of this knife is for someone who doesn’t want multiple knives, but a few that do many things.
Aug 30, 2018
PumpIron
40
Aug 30, 2018
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Deaomega1214 Hi Deoamoega1214 It's a rare pleasure to speak directly with the designer, and one who provides detailed information as well. This should be an enlightening dialogue. I'm writing as a real fan of reverse scalloped serrations actually. I find that they slice a variety of materials exceptionally well, particularly in the kitchen, with relatively few crumbs.
Let me clarify my statements about wear, and I expect we'll likely be on the same page. Normal serrations have sharp peaks that dull relatively quickly (as I imagine you mean), but protect the sharp valleys below. The valleys continue to cut material that they're exposed to, and are the area I refer to as remaining sharp longer than plain or reversed scalloped edges. By concentrating force at the small surface area of peaks, normal serrations also have a pierce/rip/sawing action in many hard or fibrous materials not possible with plain edges. This is particularly obvious with bamboo. It also leaves lots of crumbs, as you say.
Plain edges experience the same force and wear at each point along the edge, and therefore stay sharp the longest, all other things being equal (like material properties, bevel angle, and thickness behind the edge). They leave the least crumbs. They're great for chopping and push cutting, as they can make full contact with a cutting board. But without any force concentration they have difficulty penetrating hard bread crusts, and tend not to bite as deeply when slicing a great many materials.
Reverse scallops, in their various forms, are the fascinating compromise between the two. Although they do bite deeper than plain edges, they tend to cut from varied angles rather than rip/sawing through materials. As a simple matter of degree of force and wear concentration, they wear faster at their rounded peaks than plain edges, but not as fast as sharp-peaked serrations. They somewhat protect their valleys. Besides moderate force concentration, part of their cutting efficiency is likely attributable to their encountering material at varied angles on their curves. Any knife will dull if improperly cutting against ceramic plates as opposed to soft cutting boards, but it's particularly rough on reverse scallops. But treat them right and touch them up on a small ceramic rod, and they really cut, and fairly cleanly at that.
Now where wear gets complicated is in practice with varied materials. Will you make fewer cuts because each bites deeper with serrations of some type? Which handles which materials the best? Which spacing between serrations or width/curvature and prominence of serration is ideal for each material? What aspect ratios can be supported during various types of cutting by steels of varied toughness and hardness? The simple takeaway I suggest in agreement with you, is that reverse scallops are remarkably effective general slicers, and more people should try them. I'll further say they're uses are not at all limited to the kitchen.
Now for heat treatment: It is my understanding that the austenitization soak time (listed as 15-30 min by Carpenter's BD1N datasheet) is more than adequate to get a roughly equal response in thin materials like most knives. Even more so with longer tempering soak times. Heat transfer is really quite rapid in blade stock, though you still want an evenly heated furnace. The crust effect you describe I believe is more relevant in much thicker objects, hence soak times are sometimes given for varied thicknesses. I'm not saying that Rockwell testing doesn't need a little averaging, or that it can be narrowed in general production to a range of less than a point, or that it won't vary at all with geometry and location. Quenching may be a bit more rapid at the cutting edge, and other effects such as decarbeurization can occur very near the surface. I'd be interested in your response to this, but as the designer who may also observe some manufacturing, I expect you could easily answer the question whether the reverse scallops are ground hot and fast or water cooled. If you have seen edges two Rockwell points lower, and the prime suspect of hot grinding effects (either before or after heat treatment) can be ruled out, what do you suppose are the leading contributors?
As an aside, I think nitrogen steels are quite interesting. Some extra toughness and perhaps slightly lower wear have been rumored online as compared to strictly carbon carbides. Do you by chance know the toughness of BD1N at 61 or 63 HRc? At what HRc does chipping occur in fairly hard use or narrow edge angles? Aside from the slight N substitution, its composition is roughly comparable to 440C.
In the end, I think customers can be satisfied that 61 HRc really is pretty good for a kitchen knife at this price, and reverse scallops make good general slicers. I'm excited to see such a product on the market.
Aug 30, 2018
Deaomega1214
478
Apogee Culinary Designs
Aug 30, 2018
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PumpIronWell I must commend you on the most scientific response I’ve ever had. You are correct, that I agree with you on most of your points.
We do grind the blades with coolent so they do they do not overheat the blanc and mess up the heat treat. It also preserves the stones. most serrated blades edges either standard or reverse scallop, are applied with a diamond impregnated dressing wheel. It is also liquid cooled during use.
I wish you were correct on your comment about the soak. It would make life a lot easier. While 2mm stock showed less of a varianc, 2.5 to 3.5mm stock still showes as much as a 4% variance in the center.
However HRC is only one third of the equation for toughness. Carbide dispersion and grain structure or density do not have a rating system. These three components combined are what determine edge retention and toughness. Nitrogen steel reacts differently in that the nitrogen combined with the chromium and changes the molecule into what they are calling Nitrides. These nitrides provide the corrosion resistance, but without weakening the steel as chromium normally does. This is why I caution enthusiasts about being too focused on only HRC. BD1N is 5%softer than ZDP189. Yet it doesn’t chip like ZDP189 and has been shown in multiple test to hold its edge longer.
You are also also correct that the reverse scallop edge is easier to maintain with a honing rod.
Aug 30, 2018
PumpIron
40
Aug 30, 2018
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Deaomega1214 "I wish you were correct on your comment about the soak. It would make life a lot easier. While 2mm stock showed less of a varianc, 2.5 to 3.5mm stock still showes as much as a 4% variance in the center."
So this is enlightening. Thank you for the correction. You've really distinguished your product by listing different the HRC values. I've never seen that done before or heard mention that it was an issue. That's what caught my attention, along with reverse scallops and HRC 63. So are the depths you listed relevant thickness ranges of your hard "crust" for plain knife edge geometries? It must be significant if the Rc tester indentation is affected, thicker than a decarbeurization layer, which should be a few thousandths if I recall correctly.
I expect most makers are listing a value taken at the tang after a little polishing, then grinding a few thousandths off the edge in sharpening, past the decarbeurized layer. That would imply that many if not most edges may be significantly softer than listed, or will be after repeated sharpenings. Does that seem correct to you? I've noticed some factory edges lasting longer than resharpened edges, but there are many other factors, especially obtuse geometry, that would also explain it away. Of course, deeply ground serrations like your scallops would be more affected than a plain edge, but if you've encountered it, others should too.
"BD1N is 5%softer than ZDP189. Yet it doesn’t chip like ZDP189 and has been shown in multiple test to hold its edge longer."
My key remaining question is exactly how tough high hardness BD1N is. What I'd really like to see is Charpy C values for various mixed nitride steels compared to their all-carbide equivalents. Nitro-V is reported noticeably tougher than AEBL, and likely 14C28N. I haven't heard of any chipping in Z-finite/LC200N/N360, but it doesn't run as hard. BD1N is a very different sort of N steel altogether. It only has .1-.15% Nitrogen, but much more Carbon & C+N total, thus the higher attainable hardness. What does it take to chip it at HRC 63, a higher value than I've heard of these other steels achieving? BD1N far exceeds the eutectoid point and has a bit more Chromium, so it shouldn't be nearly as fine grained, and should have a much higher carbide/nitride volume and size for more wear resistance at the expense of ductility. As Chromium Carbides are prime suspects for loss of toughness, how much N is needed for the protective effect, and how protective is it? Roughly proportional to the nitride/carbide volume ratio, or possibly better?
You probably selected BD1N for the higher attainable hardness, and I presume a manageable cost. For those listening, I'm sure you've ground your knives with a geometry that won't chip under normal use, but what does it take to chip more thinly ground blades? Anecdotally even? This link http://zknives.com/knives/steels/Carpenter/cts-bd1n.shtml suggests that "At max hardness CTS-BD1N can sustain high polished, 12°-15° per side edge." Does that sound correct in your experience, even for food chopping or harder utility use? What's the thickness behind the edge on the 16° edge angle apogee dragon series, and can it be run thinner? If by chance the Charpy C is much above 30 ft*lbs at HRC 63 then it could be a bit of a leap ahead for production steels: good toughness and decent wear (at high HRc), high hardness and corrosion resistance, reasonable cost. I tend to value toughness at high hardness more than wear resistance, because it supports a more acute edge. But that's really asking a lot from a little bit of Nitrogen.
I'd like to learn more about this if you might suggest references, including BD1N testing. Thanks very much for the rare insights. Communicating with the designer is quite an opportunity.
Aug 30, 2018
PumpIron
40
Aug 31, 2018
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PumpIronAnd to anyone glancing at this long dialogue, there‘s no reason to be concerned: the hardness and wet grind check out. Rather we should appreciate the extra information provided.
Aug 31, 2018
PumpIron
40
Sep 11, 2018
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Deaomega1214Hi Deaomega12142, could you please provide a response to these inquiries about BD1N toughness and "crust" depth, as well as the promised HRc testing data that customers have been waiting for on the other Apogee knives? Thanks. https://www.massdrop.com/buy/massdrop-x-apogee-vital-8-inch-chefs-knife/talk#discussions
Sep 11, 2018
Deaomega1214
478
Apogee Culinary Designs
Sep 11, 2018
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PumpIronHi pumplron, Please understand I’m just a guy who has been manufacturing knives for thirty years. I‘m not a metalurgist. As I wrote earlier, there are no specific tests for carbide dispersion or density. We can only observe it through an electron microscope. These two factors combined with HRC is what makes Toughness. No one has created a scale for toughness. Part of the issue is that steel is an alloy not an element. In the case of BD1N there is 13% Tungsten. There is no test to tell us how much this affects toughness but it is definitely doing something. There are over 4000 recipies for steel. Who is to say which alloy is the best. Dragon knives have been on the market for four years. It’s steel has been independently tested by hundreds of independent knife users and testers. The court of public opinion shows that BD1N is one of the toughest steel ever created. After shipping over 80,000 knives made of this steel, I can tell you we have never had a return due to chipping. As far as the testing for HRC on vital is concerned that was promised by Massdrop. They must keep that promise. I know you are a person of science, and as such, you want hard numbers. However the baselines needed to give you those numbers are not yet established. As the manufacturer, the only true hard number We can give you is that we heat treat the steel blanks to 63HRC as per Carpenter ‘s specs. This is the number for this alloy that allows maxum toughness.
Sep 11, 2018
PumpIron
40
Sep 11, 2018
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Deaomega1214Thanks for the providing the information you had available. Experienced anecdotal evidence is better than nothing, & 80k is more than anecdotal, even if it's dependent upon customer reporting. FYI, Charpy testing, esp C-notch type, is a standard for bulk steel toughness testing, but it is finicky and expensive, and available data from steel producers is quite limited, so just watching for chipping is useful too. One would typically expect more toughness to occur at a lower C+N composition, like 14C28N, which is also usually run softer, but the larger carbide/nitride volume of BD1N would offer an interesting balance with higher attainable hardness and some added wear resistance. Without Vanadium to buffer the grain size, I imagine the heat treat has to be hit on the nose. Kudos for the reverse scallops and promising steel choice, and thanks for the dialogue!
Since we've chatted about the alloy composition, some may be interested in Carpenter's listing for BD1N: Carbon 0.85 to 0.95% Manganese (Maximum) 1.00% Phosphorus (Maximum) 0.030% Sulfur (Maximum) 0.010% Silicon (Maximum) 1.00% Chromium 15.00 to 17.00% Molybdenum (Maximum) 0.50% Nitrogen 0.10 to 0.15% Iron Balance
Sep 11, 2018
PumpIron
40
Sep 11, 2018
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PumpIron80,000 and no reported chipping! That's a strong track record.
Sep 11, 2018
phoenixsong
1055
Sep 13, 2018
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Deaomega1214Fair enough, you may not be a metallurgist yourself, but given that you're a veteran who's been manufacturing knives of differing metal compositions for three decades, please understand that it wouldn't surprise us consumers if you have deeper knowledge about the subject that we are unaware of, or have a metallurgist on your team who can answer those queries, or have access to some data and resources that we do not. At least for woods (some types of them), I am aware that such information is readily available. Despite this, I'd like to thank you for clarifying the potential limits of numbers and the kinds of tests in this context :)
Sep 13, 2018
BrainFlush
6860
Sep 13, 2018
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phoenixsongI love this kind of discussion. @PumpIron you seem to be well informed, like really really. That being said, everyone reading this conversation I can only say this: I have used my knife to cut a lot of meats and veggies on a restaurant scale and at home, same knife, and to this day it still can shave the hairs off my arm nearly a year later. I know it's not a scientific analysis but god damn if I am not one happy MFer for the low price of $99 I paid.
I look forward to future information as it becomes available. And to my dude Dennis, I am a fan forever. I will be attempting to buy more of your blades in time. Thanks again for the one to one that day, you're an awesome dude. PS maybe Apogee will eventually hire an in-house metal urologist if the funds are there but based on his pricing I would say he's cutting profits close especially being on MD. I could be wrong but I always give good people the benefit of the doubt.
Sep 13, 2018
PumpIron
40
Jan 7, 2019
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Deaomega1214I recently read that the HRC testing was completed on the Apogee Vital, and I'm sorry to say it sounds like a complete debacle. The heat treatment was expected to result in HRC 63, but the Rockwell results were actually 58, which is a world away. There must have been a huge error in the manufacturing process, or possibly the metallurgy, because that's not in the ballpark of normal or acceptable. If the hardness was off by 5 HRC, you can bet the grain structure is off and hardness isn't the only property affected by whatever went wrong, e.g. some reported chipping & breakage. Speculating about the cause is fairly vain: it takes serious testing and troubleshooting to resolve such matters, but this wouldn't be the first nitrogen steel that ran into unforseen complications in the HT. So the burning question that remains is the prevalence of these toughness/hardness/heat treatment/manufacturing issues. Is it limited to batches or factories or individual knives or product lines, or is it universal to Apogee BD1N knives? Is the Super Slicer affected? If the problem is not highly limited, I'm afraid it should probably be a product line or company sinker. That's a pity, as there seemed to be such potential. Reviews of the Vital gave evidence of multiple problems worthy of investigation, but I don't know the true frequency of occurrence. Occasional problems are entirely permissible, systemic ones are not. Many users who didn't complain may not have noticed that they were getting normal knife hardness, not the superior performance advertised. It made it right past manufacturing and sales until massdrop tested it after long delays. It's my hope that the matter will be fully and urgently investigated, not waiting for customer reporting or an occasional massdrop test. Further I hope that the problem is limited and resolvable, and that the steel's apparent potential can be realized. Until then, might you consider substituting something like AEBL treated to at least 61 HRC? I still like the scallops. If this truly a limited problem, then the alarm bells seeming to sound here are not relevant. I imagine we all hope to hear evidence that is the case.
Jan 7, 2019
Deaomega1214
478
Apogee Culinary Designs
Jan 13, 2019
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PumpIronI can not continue to debate theory. We must look at the facts.
  1. Apogee has always maintained the HRC goes Down after grinding.
  2. The test performed was not to industry standard. The standard is clear. The steel must be a minimum of 2mm thick, and the same thickness throughout the item being tested. The test must be performed at exactly 90 degrees on a metal surface. This is the only way energy dispersion will be accurate. Because the blade tested was below 2mm and ground into a wedge shape, it is impossible to test accurately. Again this is why no knife company tests after grinding. Imagine holding a piece of paper and someone drops a pencil from three feet. The tip of the pencil will pierce the paper. Now do the same thing, but hold five pieces of paper. The pencil will bounce off. You haven’t changed the hardness but you have changed the energy dispersion, therefore you have changed the result of the test. For testing to mean anything, it must be performed under exact conditions. The Massdrop test wasn’t because it couldn’t be.
  3. Massdrop was supplied with a letter from the factory that stated they heat treat to factory specs provided by Carpenter, and test their blanks to the industry standard. This is and continues to be the case.
  4. As I have said multiple times and will now say again. HRC is only 25% of the equation that equals edge life and toughness. The formula, the density, and carbide dispersion also must be evaluated. BD1N continues to test in the real world as one of the best performing steels of all time.
  5. Of the 2000 pieces of the vital knife ordered, we have received back four pieces. Of those three needed restraightening. It is an unfortunate fact that when it comes to reviews, if someone is unhappy, they jump to give it a negative review. When they are satisfied, not so much. Again the facts are clear here, and we stand behind the numbers.
  6. Apogee will be launching a series of videos discussing HRC, knife skills, how to properly review a knife and many others. Stay tuned.
Jan 13, 2019
BrainFlush
6860
Jan 19, 2019
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Deaomega1214I love you guys! Where's my knife set? :P Still have yet to sharpen my blade. :D Now make a mini-machete please. I need something for those Friday night fights. Hope all is well and holidays were a blast.
Jan 19, 2019
Deaomega1214
478
Apogee Culinary Designs
Jan 28, 2019
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BrainFlushThank you bud, I appreciate all of your comments
Jan 28, 2019
Narq
912
May 6, 2019
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PumpIron"...they're ground hot and fast instead of wet..." Usually, when they're ground hot and wet, they become wet.
May 6, 2019
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