Edge Geometry is EVERYTHING

Geometry Geometry Geometry
predictive CATRA found here.
knifesteelnerds.com/2018/11/1...

[@bigaspaulo]

Gives extra credence to Pete @ Cedric and Ada's 17 dps fixed angle sharpened edges for his sisal rope cutting tests. Big ups to Pete.

[@-trmxzer0-235]

Your best edge retention will always be as thin of an angle as your knife can support without being damaged cutting the hardest materials you cut on a regular basis. If you try to go 15dps and cut something hard and it's damaged instantly, go to 18dps next. Edge retention testing is important but its up to the sharpener to determine what angle best suits the specific use. That's why being able to sharpen your knives is so important. Awesome video, perfectly explained. Geometry cuts isn't just a hastag it's truth.

[@FearNoSteel]

You've been moving down the path of the Edge Jedi, respect.

[@greekveteran2715]

All true, however, carbides come into play to. I've seen huge difference between D2 and M390. If you put the same edge on the same blade and one is made of D2 and the other made of M390, you can clearly see the difference. It's so big.

[@mikafoxx2717]

Yes, but the issue is that D2 isn't very tough. So it'll chip at too thin a bevel. A steel that's all tough and not very hard​, like a 4120 at 53 Rockwell will essentially never chip, but the edge will bend if too thin. You want to find the ideal balance of edge toughness, and edge hardness, to support a fine angle. Carbides, especially not powder metallurgy ones, decrease toughness and increase hardness. Even something like 52100 steel at maybe 64 rockwell and an optimized angle will output a lot of factory edges just thanks to the good toughness and hardness.@@greekveteran2715

[@MitchBollig]

You're gonna be one of the headliners when I do my second homage to knife reviewers/channels parody. Great stuff, and thanks for the super vitrified stones!

[@rustyminer]

BBB, Love your channel. I am going to be recommending it to my subscribers and viewers.

[@wadejensen3301]

Once again, quality content backed up with data! Thank you good Sir!

[@NocturneKnives]

Very interesting video, lots of good commentary and knowledge here! Thanks for sharing with us

[@adanma17]

Great knowledge on angles steel and hrc. Thanks

[@profesorEDC]

Great info Shawn, as always. Gracias 👍

[@Montblanc1986]

Great presentation. Many makers 15-20 years ago made knives that didn’t cut at all. Even great brands like Busse Combat and Strider knives. SMFs used to have a thick cutting bevel and busse did as well. I had a Satin Jac Tac I batoned so much wood with I wore the knife into a thick convex wearing away a lot of the steel without sharpening. Making stove wood daily

[@knivesandstuff]

Love the voices. Haha. I've always gone by an adage of Murray carter's. The edge angle should be as low as you can make it on the knife you are using to cut what you need to. Cut without sustaining damage. That will always be the best performance and why hand Sharpening is the most useful tool so you can adjust as needed. What more people need to explore is how low their apexes can really go. And at what point too high a carbide prevents getting a thinner apex VS a simple steel set hard with a fine structure. It doesn't mean much if people just assume 20dps factory edges are what knives should be. What I like about the extremes you are taking with steels and heat treatments is seeing how thin and how small and edge angle a steel can take. Knives at 10-11dps just work at a level most out there don't get. I like. My knives to. Slice 0.06 kydex like it's a piece of leather.. Hard to do at 20dps

[@FearNoSteel]

That's a very interesting test Kyley, I don't think I've ever tried to cut kydex like that. Yeah, I found it infuriating when people are trying to discuss Steel but we can't even do that because everybody's angles are all over the place. I mean that's fine for day to day use there's no need to obsess about it, just go cut stuff, it's just a knife, I get it. However, if you want to try to say that a certain steel is doing something you definitely need that control to rule things out.

[@knivesandstuff]

@@FearNoSteel my favorite test because its cheaper is just the standard bamboo skewer.. cutting them at a 45 or near cross, and doing it clean without snapping the skewer.. if a knife can do that. it can do everything i need from wood, plastics, etc

[@BladeLabMiami]

@@FearNoSteel I'd go as far as to say that if you're testing edge retention, you should really sharpen on the knives on a fixed angle system, because as you point out, even if you're hand sharpening at 15°, you've probably got closer to 17° at the apex (and it's totally variable).

[@ssunfish]

Great post, for food for thought!!! Makes generic edge general purpose designs look sorta dumb!

[@ssunfish]

I like knives for skin & flesh or wood and box cutters and tungsten carbide blades for plastic and everything else, but it depends...

[@cwsmith17]

Great information. Thank you!

[@breoganlopez3943]

thanks for another interesting share and for your comments,keep on going man i really enjoy your content

[@saigudbai]

Very interesting info. I never realized before how much a lower angle can add to edge retention. I guess it's always a balance of deciding how strong you need it to be and how aggressive an angle any specific steel can hold without chipping or rolling. Not to mention what you are actually cutting.

[@joshuabriggs7114]

Great vid Shawn! Harkens back to good 'ol Cliff Stamp. Really miss that guy!

[@TonberryV]

Dude, the testing you did on the rate of sharpness loss is some amazing work. By far and away the most objective comparison between steels for practical purposes. I highly recommend anyone read your post on the spyderco forum. Top notch stuff and more accessible than a lot of technical literature.

[@nandayane]

Thanks for sharing!

[@gspam154]

Terrific video!

[@revolvermaster4939]

Wow, learned some stuff I never considered in such detail!

[@EggsAndHam22]

Shawn dropping the knowledge 🤙🏼

[@fightingusik4265]

Preach brother! I'll go so far as to say the number one lesson here, for anyone watching, is you need to sharpen your own knives! People drop hundreds of dollars on knives with no ability to sharpen them and therefore leave so much on the table. There's so much experimentation and eye-opening discovery that this "hobby" becomes an entirely new and very fun beast. I have a basic M2LW in simple BD1 that is all scratched to hell from different thinning and polishing experiments, edge angle changes, etc. I don't get a lot of edge retention out of it, but it sure is a cardboard slicing machine these days. :) I'll also say, that looking beyond geometry, that table really illustrates a lot. One might say it highlights the Trilogy Gospel: Composition, Heat Treat, and Geometry. :)

[@don0giorgio]

Hey man! Great video.

[@gaberoo9099]

Great video. Thanks for that.

[@crazywednesday]

Great explanation. Anecdotal's drive me crazy.

[@matthewp2209]

Ive always sharpened my knives flattest they could be. Knives are meant to cut and thats IT!!!

[@cis6mod]

Thumb up! GEOMETRY CUTS, Amen.

[@thiago.assumpcao]

As you said geometry is critical to evaluate edge retention. Geometry is also very important for cutting ability. A hair whittling knife will not perform well cutting hard vegetables if geometry is bad. Most western and Chinese knives would benefit from some heavy thinning.

[@tomdowser]

Hey Bear 🐻 Third time viewing this. Flippin great. Been reading your older posts on forums, again great. My question for you is outside of using a tsprof or similar guided system with radius attachment, does using a convex angle at say 3 or five degrees inclusive potentially increase the edge retention, which makes it easy, Never see people talking about that. I get its a difficult thing to execute just wondering in theory if using that would make for a sharper and longer lasting edge. In theory I think its application could work. I don't have the radius attachment yet, but when I do get one I'll experiment and do some tests. Just wondering if you have had any experience and your thoughts. Allow me to say your a pillar in the community and lots of unknown to you people appreciate your thoughts and explanations. Cheers.

[@6mmFilms]

Straight up truth!

[@kennymanchester]

Pretty interesting presentation. It feeds my “Nerd Knife Guy” side of my brain! I can’t talk with anyone around me about stuff like this or their eyes glaze over and I lose em. LOL. They just know that their knives are sharp when I do my thing for their babies. I decided quite some time ago that I simply cannot get enough precision by hand on my stones and must use my FA system where I can measure a fixed point with a digital gauge and know for certain that I’m getting 15 degrees per side. The Edge Pro is nowhere near as fun or as fast as Freehand, but the results are precise and repeatable. I keep a file on knives for re-sharpening repeat business so I can quickly replicate previous angle(s) or adjust angle depending on owner feedback. Is that too nerdy?

[@sgsheff]

This is so cool

[@ssunfish]

Damn, I kinda gave up on high performance because I figured it was too many variables. Got so many bars of different alloys and thicknesses because I wanted to try higher Rockwell. Now I see how much above S35VN that Magnacut is and how much geometry is super influencing. Before I just heard Ed Fowler talking about "the best edge that specific knife could support" when he sharpened some neighbors cheap K Bar. It's more than design of knife, alloy and grind, stock thickness, geometry does more and that can be changed on a knife in hand for immediate feedback! It's not so simple as just have a tough alloy, still no one Uber alloy for every knife, but any specific knife can be worked on and experimented on to make it work it's best for what the owner wants to do! This means one doesn't have to give up corrosion resistance as something sacrificial for way ore in return! I have ( from this video) so much more to remember and consider!!! THANK YOU

[@jasonerickson1033]

Great info 👍

[@EngineersPerspective701]

Well said!

[@Triple.Stripe.Knives]

Super cool test sir! Great to see the info like that. How would you say edge thickness plays into that? Or does thickness BTE not do anything to edge retention, just slicing?

[@FearNoSteel]

It depends on what you're cutting but behind the edge thickness is certainly important. It's not going to change how your edge dulls directly but it does improve the cutting ability of the overall blade. I mean for some knives, if you just have super thin behind the edge thickness and a dull edge you'll find there's things that you can still keep cutting through. I think another important factor is that if a knife is thinner behind the edge, it's easier to freehand sharpen. And if something's easier to sharpen it means you'll have a sharper edge, if you have a sharper edge you're further from being dull, and if you further from being dull, you're going to get more edge retention.

[@GunnysSharptalk]

Amen! I try to get people to understand that all the time. Without proper geometry everything else become much less important.

[@dayannahkali]

Awsome ! Catra test abrasion resistance, wich is a third of what constitute edge stability, the others are hardness and toughness. That determines really how low of an angle you can put on your blade. I wish I had the nubers for factoring that in acurately. Super tough but too soft can't go too low, hard and brittle same. If say the edge on your 52100 at 12 dps is as stable as your maxamet at 20 dps, is the price difference justified ?

[@AaronJohnson1979]

Love this video! What is the tool you need to measure edge angles I see you using some thing in your videos looks like a laser or something

[@AaronJohnson1979]

Never mind I looked it up lol “Goniometers”

[@Chris_229]

I’m with you. Not to mention that shot really ain’t safe to be breathing in

[@Nudel-nc1cp]

Great stuff BBB. I just wonder what cpm-rex121 can do at 11-12 dps? :D

[@ryewaldman2214]

One of the alternative takes on this is that since small changes in the edge geometry can so easily shuffle the order of the steels in terms of TCC, that all of these steels are more or less the equivalent in TCC performance potential given these assumed heat treat protocols and assuming the carbide content is relatively accurate for the heat treat (obviously, not 52100). But i think most of us watching the video already knew this. Here, toughness, edge stability, and stainlessness are the real factors that would steer the maker or user towards one steel over another given the knife application, since TCC (as the proxy metric for the unscientific "wear resistance") can so easily be tweaked one way or another by geometry, etc.

[@ryewaldman2214]

One of the things that I think would be a really cool study (that i don't have the equipment for) is to take a closer look at this regression and the input variables to it. Namely, to look at the uncertainty in the inputs of this regression equation and try to quantify what the amount of uncertainty is associated with each of the inputs. HRC, what is the uncertainty a maker has in a knife blades HRC? it would likely be a specific number to each maker+steel+treatment. If a batch of 10 knives of the same steel come back with HRC 62 +/- 1 HRC (standard deviation, extreme spread, etc) and to propagate that uncertainty through the regression, then you get an idea on the range of TCC performance you'd expect a single batch of knives to exhibit. Same with carbide makeup, and this starts to complicate the analysis because it is likely correlated with the variation in HRC since both of those are varying according to the heat treat. Edge angle is another one, not everybody has a goniometer suitable for knife edge measurement. I'm not actually sure how much of the apex is phsyically worn away during a CATRA test, but when edges get stropped and microconvexed or microbeveled, whether or not the extent of that micro geometry is smaller, larger, or of the same order as the actual wear at the edge apex during a tcc test, but it definitely introduces uncertainty in the edge angle as well. In practice, i suspect the average free-hand sharpener (like myself) can't read the edge angle from a laser goniometer better than +/- 1degree, and that there will be small variation in the angle along the edge and up the edge. All of these will lead to real experienced variability in the TCC between seemingly identical knives, and i suspect that the total variation between "identical" samples is often similar if not greater than the theoretical variation between different steel chemistries, especially the closely related steels, e.g., s30v-s35vn-s45vn family, etc.

[@FearNoSteel]

I don't doubt that there are things that can be done to refine things but I think it gives a good idea about the differences between things and how carbides hardness and edge angle have an effect on edge retention. I feel what's needed is more testing for data which can be used to build other regressions for other things but that will cost lots of time and money.

[@ssunfish]

You said what I was trying to say so much better!

[@bazzzker]

Edge geometry, blade geometry, blade material, cutting material, hardness, hardening process, what was used to sharpen and how. Lot of variables

[@FearNoSteel]

Sure, but that doesn't mean we should stop trying to isolate things and rule things out to understand how things work so when things come up, we know the reason why things are different.

[@jmarsh667]

I couldn't agree more with you BBB also I'm with the other guy always trying to go as low as I can for the job even if that sometimes means using a less carbide rich steel for a finer carbide run hard with low angles

[@knifesharpeningnorway]

Jupp always said it thin your blades and lower the angle its makes a huuuuge impact.

[@sgsheff]

This is some powerful stuff

[@DelYourself]

Now that we know the importance of edge geometry the question is... which steel would suit typical EDC needs (without stupid things) 'best'? I mean specifically the ratio between toughness and edge retention. Is Maxamet the way to go? Or would I have pretty much similar results with Z-Tuff? Or maybe for an average user it would be best to look somewhere in between (M4, Cruwear)? I guess what I'm trying to ask is: is it possible to have the same cutting performance(edge retention/toughness) with all the steels listed above by simply manipulating the sharpening angle?

[@kane2298]

I just bought a cheap 60x microscope, and have been looking at my edges. I was surprised to see a lot of what looks like chipping. Small enough you can't really see at 30x. These aren't hard use knives, and I most are around 17 degrees per side. I was thinking about going to 20dps to see if it made any difference. After seeing your video, that's not something I really want to do though. Maybe I'm looking at carbide tear out and not chipping, I'm not sure??? Mostly s30V, m390, and 3v.

[@FearNoSteel]

Man you're never going to know unless you try you can always go back and forth between them as you use your knives see what works best for you

[@kmopm777]

What activity did chip your knife?

[@kane2298]

@@kmopm777 That's the thing, I these weren't beaters. I don't think anything I used them for should have caused chipping. Keep in mind I'm talking about chips you can't see with the naked eye.

[@jmarsh667]

@@kane2298 I know exactly what your talking about even just cutting card board. It seems to be micro chipping or mashing of the edge from a hard particle or maybe carbide tear out it seems to happen to carbide heavy steels like S90v and m390/S110v more so than others. I need to do more testing to say for sure.

[@kennethbrown445]

Any way we could get a link to the spreadsheet?

[@Doinitwell007]

Dude you’re comparing different angles to each other I just wanna know what’s the best if all knives are the same . In your opinion what is the best 6 1/2 inch fix blade for Ed retention and resisting breaking at 20° per side and 3/16 thick oh and 61 hardness

[@danbarnum8997]

You da man!

[@AustinMuellerHandmade]

Hey Shawn, I didn't realize this tool was available, and I appreciate you pointing it out, I'll have to go play with it! I am very curious about something you touch on a couple times in this video, and I would like it if you could shed some light on it for me as I respect your opinion. Are you saying that a larger edge angle causes the apex to widen faster than a lower edge angle during the CATRA test, when you said, "Lower angle maintains a smaller radius better than a thicker angle" and "Having a thicker angle, it's easier for edge apex radius to get wider when the dulling and wear start to happen at your edge" This seems to be at odds with Dr. Larrin's test results where he states "There was a difference in final thickness of the apex of the edge after the knives were run through the CATRA test. The 20° edge was about 23 microns after the test, 34 degrees led to about 19-20 microns, and the 50° were around 16-17 microns. All of these images are of the ingot 154CM steel. So it appears that with a lower angle edge it can wear down to a larger apex and still maintain better cutting ability than a higher angle edge." Are you both talking about different processes of wear and cutting, did he get uncommon results in his test, or are there differing opinions on how different edge angles wear and what actually contributes to the ability of an edge to preform optimally over time? Thanks for the content and discussion!

[@FearNoSteel]

Yeah that's interesting, that's something that can be explored in the future

[@knivesandstuff]

Both are probably correct. The thinner bevel has less force going through the material because of the thinner apex letting the apex get wider before the effort reaches the stopping point. The wider obtuse edge has less wear and thickening on the apex before the force threshold of catra is met because of the effort of the wider bevel

[@FearNoSteel]

Maybe we can get Todd Simpson's help for something like that

[@minibuns6220]

Where can we download the spreadsheet? Thank you

[@londiniumarmoury7037]

I'd like to see what your Magna can do at beefy unnecessary angles, 40 degree (per side not inclusive lol) I bet it could cut through some serious shite.

[@londiniumarmoury7037]

Do it and hammer through a quench plate or something lol.

[@sgsheff]

Amen

[@ilyas859]

When I hear "geometry cuts" I think about the entire blade - from spine to edge; is that wrong? I've heard about how spydiechefs re-ground to a thinner blade need a blunter angle on the edge and would out-cut other knives with thinner edges (and thicker blades)

[@FearNoSteel]

It applies to everything man I'm just giving the edge angle some love

[@greekveteran2715]

@@Butch_Deezlsteak Stropping has probably blend that angles to a convex edge, and that's what makes edge hold longer and in the same time, adds more edge stability. Microbevels are still a flat "V" edge, that doesn't provide what most people think it does, it's the convexing that adds. Factories just put that kind of edges, because it's the fastest way to put an edge, to keep up with the constant demand, of their mass produced knives.

[@greekveteran2715]

@@Butch_DeezlsteakYou didn't say you put a convex edge to upgrade your knives performance, you said you put a secondary microbevel. I just mentioned that, mostly for people who think, that any flat edge, is better than a convex. Most people add microbevels, to strengthen an edge, but that's not true, it's the convex geometry that adds, not the microbevels...

[@sgsheff]

I'd love to see maxamet change depending on angle

[@FearNoSteel]

With how powerful geometry is, steel and hardness aren't going to overtake it. That's why you would take Maxamet and put a lower angle on it too and than you win at edge retention.

[@felurianmasters4369]

This data is exactly contradicting my prior belief. Thank you for sharing this info.

[@stevenbusch9336]

🤘🏼

[@mikeking6686]

WHAT knivesandstuff SAID

[@steeltoez8345]

I think its important to seperate anectdotal style testing from controlled versions. Controlled testing has to be specific on as many points of contention as possible. Anectdotal is a byproduct of just putting use on the knife. Thats how i view it. Controlled testing for me was always boring. And too much focus was centered on numbers versus the joy thru use. And the journey to squeeze out as much performance/preference as possible. Otherwise i bought a paperweight, and will never recriprocate value from the purchase cost.

[@FearNoSteel]

I think with controlled testing, you're trying to compare differences between things you build a data set to explore, usually one thing at a time. Anecdotal testing, there's nothing wrong with it that's more of just your experience of enjoying the knife. The problem is mixing those up those things it's difficult to make conclusions about things if you're not using control, but it's difficult to enjoy using the knife if you're using control. They go hand in hand but they are separate like you say.

[@Barryhatchet]

Interesting that you need to adjust your angle to the steel.

[@FearNoSteel]

Mostly needs to be adjusted to the user and how they use it and for what they use it for. If somebody wants to use their knife like a "toilet wand" and do dumb shit, then they don't really get a choice. They need a thicker angle until they want to start using it like a knife again. Knives are for cutting. However, that's the best part, edge angle is highly customizable. Yet, everybody blames the steel for things without ever ruling out the edge angle they need for what they're doing.

[@lashazaridze813]

This is stupid simple yet so somplicated for some ppl to understand :D

[@dominicdwk]

Love the information but there isn’t a single actual knife blade with an edge angle in the video.

[@Rammer_Jammer]

🍻

[@mr.e9017]

Mister knife steel nerd should design a knife.

[@FearNoSteel]

I believe he gets more pleasure out of designing Knife Steel, and God knows we need it cause he's the best there is at it.

[@mr.e9017]

I bet you could design a knife that many would want. Which steel, which angle. Putting all you knife science to work.👍

[@sharamkh]

@@mr.e9017 Triple B does design and make his own knives and it looks like solid quality. I can’t afford them unfortunately, but I can drool 🤤😛

[@harrisquicksilver6595]

Omg i love when brains beats ignorance, its a beautiful thing when arrogance gets schooled. Thanks my intelligent friends

[@adoseofdrew]

M’Fer, whaaaaat? 🤣🤣😎👍🏼🙏🏼🖖🏻

[@johnnyutah565]

Great video not a knife maker butt I still enjoyed

[@FearNoSteel]

Yup, I mean edge angle is user responsibility, not maker responsibility.

[@TopDog8762]

Thanks for schooling.

[@tacticalcenter8658]

Spyderco USA m390 is good. Proven by outpost76 also. Too bad other m390 is not that fortunate. Most other brands do a different heat treatment protocol and or burn the heck out of the edges.

[@Kyrazlan]

🤣 thanks for the video.

[@jonathanwright3273]

Informative and spot on with your data. Not that it offends me personally but I don't think dropping the F-bomd is actually truly supporting your goals.

[@FearNoSteel]

I don't want you guys to forget who I am I'm not a white lab coat or a white collar guy, I think that there's plenty of people that present a cleaner message and are a lot more professional. I'd rather speak freely and candidly. Just pretend like we're having this conversation in a bar over several pints. Or in the gym in between sets on the bench press. I'm just going to be myself man.

[@jonathanwright3273]

@@FearNoSteel worth note in that we are not in a bar or in the gym. This is a public forum. Suggest you keep the f-bomds to the bar, gym and suck like places. The point is that it's just not nessasary to be droping the f-bomb in a very public enviroment. The intent, message and objective of your wonderfull video simply does not need f-bombing. In the end I'm just giving you food for thought, maybe this enlightens you to take a diffrent aporach or it does not. Either way your video is spot on and when these formulas were released I did exactly what you did in excel and plotted knife angle vs TCC in 0.5HRC steps for a given knife steel. I'm trying to figure out how to bring toughness into this equation.... but I think I need to speak to Dr. L Thomas on this.

[@FearNoSteel]

I appreciate your candor and hopefully you can appreciate mine. I am me. It's not a matter of talking to somebody for getting toughness into it, it's a matter of doing something. Won't be a way to translate the toughness testing unless there's actual physical edges being tested with quantifiable data that can be used for a regression. The impact charpy testing is not changing with edge angle, just hardness etc, however, geometry is a bigger factor. Perhaps in the future work will be done for that but thats a lot of work and that time could be used for more lucrative projects. There's nothing stopping anybody from doing it, perhaps something you can do? You're probably better at not having a potty mouth too haha

[@FearNoSteel]

We may not be at a bar or in a gym but we are on my fucking KZbin channel. Hahaha

[@FearNoSteel]

In my life experience, I found that people who don't curse are holding back and in a lot of ways are full of shit, I like when people are open and honest about who they are and what they are about. I feel you find somebody that censors themselves and they're censoring more than just their language, they're censoring who they are and that could bad, hiding some kind of hidden agenda or ulterior motive. So I find cursing really weeds people out even if it narrows the audience I'm not concerned with being the most popular person in the world. I'm just concerned with being myself.

[@newmanoutdoorsnewman5619]

Hey

[@chucknunface]

But muh real world

[@FearNoSteel]

"Nobody fucks wit muh real world!" *unsubscribe

[@greggschachterleppc2769]

Interesting content. Lost me me with schoolyard potty mouth. You’re obviously intelligent, you can do better. I’d love to visit your channel again. You can do it!!!

[@FearNoSteel]

It is what it is. I think you'll find other channels that will give tou what you're looking for

[@timoteus011]

Why so rude? Interesting content but don’t like your speech