The Toothy Edge Fallacy

[@jakehu6671]

Man, I love dynamic between image and voice over. Great presentation!

[@stroppystuff641]

Thanks Jake! Greatly appreciated the feedback especially when it's positive!

[@jasonpez3294]

It is a rare knife KZbinr who uses modern peer reviewed scientific reality instead of either winging it their first or second time and passing it off as an instructional video; or sticking to the assertions of what grandpappy always used to say (long before 440C was considered THE knife super steel). On behalf of the sharpening/blade world I THANK you for making THE most concise but still absolutely thorough AND scientifically illustrated videos I have ever seen on KZbin about ANYTHING knife related (save for the King himself: Dr Larrin Thomas, but I feel like I deserve an honorary metallurgist degree for the research I ended up doing to understand everything; despite his best efforts to dumb it down for us mortals). This is a topic I’ve been tormented with for a while and couldn’t find anything remotely legitimate, I even bought digital microscopes (which weren’t nearly micro enough). You’ve covered every thought, idea and logical fallacy I’ve heard or had, and stopped me wasting further money on higher micron diamonds and pastes etc., (through this video and also the other one testing one micron back to 6, back to one, just gold). Absolutely flawless videos; and without the need for the flair to fill the absence of knowledge and expertise like most other KZbinrs we have to sift through! Keep up the great work mate, if I could afford to donate I would, but unfortunately I wasted all my money on high micron diamond powders and pastes lol, hopefully this comment helps, if I stumble on any more tosser videos I’ll be sure to direct people here!

[@stroppystuff641]

Thank you for such kind feedback I really appreciate it and I'm glad it was interesting to you. I get so much frustration from watching people parrot garbage information on youtube which is not usually only wrong but they don't even understand what they're saying. It drives me to make some of these videos. For example if a big youtuber says to use 9um for a toothy edge and a customer buys 9um Stroppy Stuff, they're going to come complaining to ME when it doesn't do what they thought it would. So I have to try and fight back against all the BS.

[@homeslicesharpening]

Great video bro - thanks for summarizing Todd's new article and helping lend clarity to what has been discovered through Todd's SEM and general dual grit research. I appreciate your clarity both on the inappropriately bad rap that fine edges get (which is to say - thanks for asserting that fine edges can perform very well and usually the belief to the contrary is due to sharpening errors, I agree). Also, thanks for clarifying that although toothy edges don't work for the reasons we imagine, they are exceptionally practical for many cutting tasks. Superb video Max. Thanks.

[@stroppystuff641]

Thanks for the support Gabe! I also run aggressive edges on all my edc tools too. I only really finish my leather tools to a fine grit and also when I'm chasing a new Bess record 😅 I had to make this video because I get lots of customers asking if 9um is the right compound for a toothy edge. It's hard to explain why 9um actually gives a smooth edge without sharing the work from yourself and Todd.

[@TodorTashev]

Finally somebody who is speaking advanced sharpening/stropping language!

[@lars43771]

Very well done video! I really appreciate this one. Even though it has been disproven multiple times, well known “sharpeners” still indeed tell you to strop some teeth back into that edge. Hope we can let this finally go to rest now. A true “toothy” edge is very easily stropped away. Even on 1 micron this goes rather quickly.

[@CNYKnifeNut]

No chance whatsoever. SOS has already debunked a ton of things that still get parroted around as truth.

[@stroppystuff641]

@@CNYKnifeNut So true. But at least I can stop explaining it over email now and just link people the video :(

[@John..18]

Great video as always, 👍,, There is so much BS around on sharpening in general, (imho).. Cheers,, John..

[@Falin89]

Thank you for the very nice explanation and trying to stop the spread of misinformation and lore based on imagination or lack of knowledge. Very smart to use a cotton ball btw. Keep up the great work!

[@stroppystuff641]

Yeah the cotton wool idea wasn't even mine either 😭. Rian suggested it to me

[@chanabhaji2726]

Starting to sink in, thanks for letting us know where not to go wrong whilst sharpening.

[@KnifeNinjaEDC]

Good info Max. Always helps me rethink my misconceptions and figure out anything I may be doing wrong.

[@slipperysteve2513]

I need more videos on toothy edges. There is nothing that erks me more than when I sharpen a knife to hair shaving sharp, yet it just glides across rope. I keep doing this to my S30V, but not my CPM-3V knives. It’s like something about S30V gets too polished at the very edge and loses all of its teeth.

[@glockgaston2922]

Really good video and explanation thanks for sharing !!

[@stroppystuff641]

Glad you enjoyed it!

[@Snarlacc]

Thanks, I thought I was going mad. I have been messing around with 400-600 grit diamond stone edges as of late (with normal sharpening stones I feel like it's half as agressive as diamonds are, my 2k diamonds look like what you get from a 1k shapton). It always was easier for me to get polished edges but I wanted to try out toothy, and as you say, any time I strop the teeth go away fast. I found I had to practically leave it as it comes from the stone. A rough side strop without compound can work too. EDIT: Someone said to use fine stropping compound and that this works, but even my 0,25µm diamond strop pulled the teeth fast. The reasons for toothy trials for me were: Firstly on 440C it's relatively hard for me to get a good razor (compared to 12C27, AUS8, carbon or even D2 and S90V) and since toothy is faster I wanted to see if I like it better. Still not 100% sure I like toothy better than polished. Secondly I found an old, cheap knife that can't handle a razor edge, it dulls instantly, and I wanted to see if teeth help. It's probably 55HRC 420 steel and the teeth actually don't prolong edge retention by much. The steel needs to have the standing potential as well, else it don't matter much.

[@sharpwhits0167]

Your videos are amazing. You provide a deeper understanding of what is going on at the apex of your knife in a way that is easy to understand. Thank you!

[@stroppystuff641]

Thank you for the support 😊

[@kilovolt88]

I pick the same scales for my spydercos too, nice

[@JohnDoe-zb7dz]

This information will crumble the stable datum of high profile knife/sharpening channels who subscribe to stropping teeth onto an edge. The burr is the bite.

[@sabelfechter7136]

I cant thank you enough, this was exactly what i quessed over the past few years, after reading some earlier articles of him, but never was 100% sure, as then he was more focused on razors and i wasnt sure how well it translates. Within watching a few of your videos on these key topics, you became one of my favorite channels. 👍

[@stroppystuff641]

Thank you for the support I really appreciate it!

[@DerekeBennett-j9q]

I actually bought 10 micron gunny juice to see if i could strop a toothy edge back on, it did not work, as a matter of fact it seems to just dull my really sharp knives,

[@chipe420]

Great video, it’s definitely hard for beginners like me to tell what’s going on without experts and microscope imagery like this. Very good advice on not polishing over the apex

[@JaDoN_Klltt]

You are really instructive, love the vids. I am still learning very slowly how to sharpen on kme and am still amatuer at best.(I have watched some of the content) Thanks for the info spread and still need to get from your shop!!!

[@stroppystuff641]

Thanks for the support! Great to see some of the information has been useful

[@robbabcock_]

Great video! I'm a chef and an avid knife nerd that seems to be in the minority but I like a highly polished edge for virtually everything. My own knives get sharpened to a 10k finish on a Naniwa Chocera 10,000 grit and stropped with 1/8 micron CBN on 'roo leather.

[@jiahaotan696]

What do you cut? How long do your edges last before you need to sharpen?

[@jeffhicks8428]

you are ofc 100% correct about everything you said in this video

[@EdgeStoneKnives]

Another killer video and truth reveal. Doing the Lord's work yet again haha.

[@SlashGears]

Hey man awesome looking manix2. What AWT finish are those?

[@stroppystuff641]

They're stonewashed raw aluminium :)

[@jeffhicks8428]

a toothy edge imo is something different from "bite." Imo bite is just a casual way of saying cut initiation, which is function of edge keenness, which is a function of literally the radius of the apex. that is what keenness is on a physical, measurable, empirical level. that's what tests like bess are for, estimates or proxies for the radius of the apex. the more acute, ie the smaller the radius of the apex the keener the edge, the more it "bites" into things because it quite literally has higher cut initiation, which is a technical term. cut initiation and cutting ability are different things, most casuals don't understand this either. cutting ability is more a function of geometry than it is the edge keenness. as for a "toothy edge." the fact of the matter is that a 120 grit edge will score 50% higher on a catra test than a polished edge. that's a toothy edge. once you get to 400 grit or above, there is minimal difference in catra results vs polished. anything

[@edwardg.135]

I think that toothy edges can be slightly finer, potentially up to 1000 grit depending on the steel. I'm not sure about the catra retention, but I also think for many courser steels, straight edge retention doesn't have the greatest importance. I feel coarser steels with a tootier edge have far better response to stroping than a finer edge, which I believe to be the most important aspect and what gives the toother edge it's edge retention advantage. Because of this, I feel that an edge just isn't strong enough below 400 grit and looses out on some of the benefits, but maby there are other applications where the tradeoff is desired.

[@jasonpez3294]

I don’t know what you’re referring to in the first half; like bite, cut initiation vs cutting ability etc., maybe they are industry slang for things that are covered scientifically in the video (maybe mirror polish vs toothy respectively?), but Dr Larrin Thomas said the best CATRA results he could get were with 400 grit; but I don’t remember what steel it was which brings me to my next point; everything you just wrote is non steel specific… There used to be not a huge bracket of toughness and edge retention back when 1% was a huge amount of Carbon in knife steels, then you could make such generalisations; but now there are knives made from steels like NitroV or 14C28N (similar performance to older steels) all the way to 15V, Rex121, and straight up Tungsten Carbide Steel at HRC of about 70. What you’ve written towards the end may be the case for some steels, but you cannot generalise a particular edge is best for every steel; even on a standardised medium like CATRA, because the differences in composition and microstructure can flip optimal edge structure results on their heads, also dependent heat treatment etc. Blade metallurgy is in the middle of an explosive era where many old rules no longer apply across the board. I’ve seen professional knife sharpeners destroying super steel knives on a portable belt grinder and other electric equipment without cooling the blade at all. The knife sharpening industry is becoming dangerously outdated because everything is changing with new knowledge and new blade steels, beyond our wildest imaginations even 20-30 years ago.

[@DroggeIbecher]

hmmm so i should go get a fine edge on my chisels and planes? nice, a good reason to train more :D

[@jarrettm3728]

How coarse can u go to cut the best without loosing edge retention?

[@kyounokaze]

Thanks for the great video

[@robthompson8285]

You should make an ASMR channel with your voice. Also, you make great stropping compounds 😊😊

[@stroppystuff641]

Thanks man 🙏 very kind

[@HamBone86]

What is ASMR?

[@robthompson8285]

@@HamBone86 It's like meditation channels. People listen to them to go to sleep and stuff.

[@floraly88]

This flew way over my head. In the hand drawn sketches from the Home Slice you can see the micro-serrations being 23 microns. So why wouldn't I be able to strop these in with a coarse compound? There's obviously so much more I need to learn but at the same time it seems that most of the knife/sharpening community is just trial and error as well. To me it feels like some "official" knowledge is missing. Like researched textbook knowledge the way one could find it in any other field.

[@stroppystuff641]

@@floraly88 the reason you can't strop the tooth in is because the image from the home slice is not correct, it was his assumption. We do have official knowledge and it comes from the Science of Sharon website which I was referencing.

[@floraly88]

@@stroppystuff641 Thanks, I'm going to read into it a little more. Im only into sharpening for a year now, and the way I see it it, it'll be a long learning journey. What I meant with official knowledge was like something along the lines of math, physics etc. were there is a textbook with some fundamental that are facts. You just learn them. While in the knife community, I see a lot of guesswork and personal interpretation as well as a lot of testing. In other fields, you don't see nobody testing the fundamentals anymore, as there already is an objective truth. But again, that's not meant in a negative way, only my observation so far.

[@stroppystuff641]

@@floraly88 I do understand what you're saying and I agree, most people also spread incorrect information too. However Science Of Sharp has a lot of very solid information backed by SEM images. It's the best source of information we have

[@NonScientificBladeTesting]

You're the man!!

[@SkunkPunch73]

Fair play this is a beautiful piece but the part I find so wholesome is other than the incredibly pin point information is the ever so detectable for the millionth time I am going to tell you all yet again but please I hope you let my words sink into your minds this time👍🏼 the joy of all the people who know nothing but argue with people that do about everything!! Once again thank you for such a beautiful piece 🫵🏻😘👍🏼 Have a cracking up coming weekend 🍻🥃

[@stroppystuff641]

Haha how could you tell! I've basically typed this whole thing out to customers over email about a hundred times and I'm bored of saying it 🤣. I don't want people to buy the wrong products and then be disappointed with the results. Thanks for the support man

[@SkunkPunch73]

@@stroppystuff641 hahahaha you’re more than welcome my friend. I personally would have been sat in a corner just dribbling and making the odd strange noise from time to time after what I can only imagine was like being back in school! 🫵🏻👍🏼 keep on keeping on 😂

[@ironfoot1938]

Well I do love my knives whithout any burr, and I also think it makes less sense to leave a burr (because of rolling), but this was very interresting

[@stroppystuff641]

The point is that if you have a toothy edge then you do in fact have burr. Most people don't realise they're not burr free (not saying that includes you)

[@krystofmraz]

Its the matter of what you Cut. JUST note that some traditional tools Are designed to Cut with bur. Scraping card for example, or i believe even scythe.

[@ironfoot1938]

@@krystofmrazI mean yes, but a Scraping card isn't a knife. I don't think there are many tools that really benefit from a burr.(mostly because it doesn't hold very long)

[@krystofmraz]

@@ironfoot1938 IT gets dull fast, but also Can be made Fast. I think IT JUST depends on application of the knife, because lets be honest, Its one of most Diverse tools And each really Can be used for absolutely different work. I JUST want to say that Its kind of stupid to deny the burr cutting As totaly Wrong when you Can see on some examples IT works well. Also i do believe Its actually what you Are making with steel rod on butcher knives - JUST toothy burr. And honestly, for stringy And not So hard material Like me, IT sounds reasonable. Also when someone Is butchering 40 Hours a week, je probably dont use something not really working.

[@ironfoot1938]

@@krystofmraz fair enough. BTW StroppyStuff mad a video a month ago about steels. You can make burr free edges with a steel, at least thats what he shows kzbin.info/www/bejne/sF7OlpiqYsx7aJI

[@BladeLabMiami]

I'm not sure I'm following the explanation. If the micron size of the stropping compound abrasive doesn't correlate to toothiness ... why does the micron size of the sharpening stone abrasive correlate to toothiness?

[@stroppystuff641]

Because the burr created the tooth. You can't build a 2+ micron thick burr via stropping. A thin foil burr can be created via stropping however this is not strong enough to be used as a cutting edge. The abrasive particle does not cut a tooth. Burr fragments are left over from very coarse stones which physically cannot deburr to a razor style edge without progressing to finer stones.

[@BladeLabMiami]

@@stroppystuff641 Probably not, but I guess it depends a lot on the substrate you're stropping on. I think you could create a pretty durable burr stropping with 20 micron on a hard wood like oak. But who does that? lol

[@stroppystuff641]

@@BladeLabMiami 20 microns is still not coarse enough to create a burr this thick and durable

[@lars43771]

Stropping on a a substrate that has give to it, can not result into a larger/thicker burr. The apex on a microscopic level is being slightly rounded off, a small foil burr can be created under the right circumstances, but these are definitely not beneficial.

[@stroppystuff641]

@@BladeLabMiami 150 micron compound on a steel lapping plate might get you close

[@billmanning8806]

I shoot for toothy but with no burr. Further contemplating the process to de-burr, I am beginning to think edge leading is probably best because it has a better chance to abrade the burr off while edge trailing would probably (mostly) push it to the other side. So ...edge leading for burr removal... have any thoughts? (Thanks, good and thought provoking video.)

[@4d4mko]

Not sure to understand everything, each sharpener that i looked tells us that burr=bad=weak apex... I have tried that technique with Maxamet 230JIS + 1u strop, i was not happy with the results... 700JIS + 1u strop is much better and also strops back better!

[@stroppystuff641]

A burr is anything outside of the sharpening triangle. The word "burr" can cover so many different classifications. Most KZbinrs have no idea what they're talking about however so will say all burrs are bad. In reality a class 4 burr can provide longer edge retention than a razor type edge. It's a thin edge which extends past the apex, so you abrade the strong 2-3mircon thick burr and then get to the apex and can abrade that also. The dual grit sharpening method has been known to produce some of the longest lasting edges ever tested and that produces 2 burrs. A thick burr off the apex and a thinner burr off that burr.

[@krystofmraz]

Nice. I do believe that the best example of this Is using steel rod Like butchers do. IT makes this toothy edge, which basicaly Is made From bigger burs able to withstand cutting.

[@Ajaxykins]

I think I'm not following you on something technique related. You say that micro serrations can't be made via channel from the abrasive, but my technique for making micro serrations I think very clearly does so, with the edge shaped the way a serrated steak knife would be. I do this by thinning the primary bevel at like 8-10 degrees per side, then by utilizing a 36-80 grit stone or sand paper use 1-2 high pressure edge trailing strokes at 25-35 degrees per side then strop on some compound for a few strokes (as to not remove teeth but remove some of the burr). The resulting edge definitely has "tooth" as well as probably a good bit of burr, but most definitely seems to have teeth also created by the channels left from the much coarser grit than you are using. I think factory edges from case knives used to use this same style by sharpening on a low grit belt (36 grit) then hitting it on a buffing wheel making a micro-serrated edge

[@stroppystuff641]

The height variations are caused by burr fragments. As you can see in the SEM images the low spots in the apex do not correlate with the channels carved by the abrasives. The reason the coarse stones make good serrations is because they create a thick burr which can stand up strong and not appear to be a burr unless inspected with SEM.

[@Ajaxykins]

@@stroppystuff641 Can there not be more than one way to make height variations? Scratch pattern and individual scratches them selves are visible to the naked eye with 36 grit, and at a steep microbevel like 30+ degrees per side on a thin 8 DPS primary grind. Maybe at 300+ grit and 17 dps burr formation is the sole way of creating height variation, but at a steeper angle with much coarser grit I can't imagine that the channels themselves do not form a micro serration.

[@stroppystuff641]

@@Ajaxykins 36 grit jis is so unbelievably coarse that I'm sure the abrasives would cut low spots into the apex yes. But nobody is finishing their knives at 36grit. The purpose of this video was to explain that stropping compounds and high grit stones cannot form a toothy edge. The toothy edge is formed on coarse stones. Finishing on a stone as coarse as 36jis would severely sacrifice sharpness in exchange for a saw blade.

[@Ajaxykins]

@@stroppystuff641 Jeez am I such a nobody? Probably so haha I finish my table knives like this for the same reasons that serrated knives are the standard. Edge lasts longer on ceramic plates, cuts through rolls and biscuits with a sawing motion as not to squish them, and works well on meats. 36 grit (FEPA-F) microbevel touches up with 2-3 strokes per side and some quick stropping after a few meals of being blunted on ceramic plates! But anyways you did indeed prove your point about fine stones being unable to make a toothy edge On everything else I'm more of a fine edge man

[@stroppystuff641]

@@Ajaxykins yeah agreed I wouldn't be putting a fine edge on a table knife at all either.

[@teresashinkansen9402]

Toothy edges are crutches for people who lack good sharpening skills. Rarely have found real use cases for toothy edges other than cutting ropes and sinew with a relatively dull edge.

[@Aerzon1v1]

What do you mean by that? Do you mean toothy edges in the real sense, as in forming a sharpened burr? Or do you mean simply sharpening on coarse abrasives without progressing to finishing stones?

[@teresashinkansen9402]

@@Aerzon1v1 I mean, sharpening on coarse abrasives without progressing to finishing stones

[@metagen77]

Another paper cutter yaaaawn

[@verdigrissirgidrev4152]

woodcarving tools are not exclusively used with push cuts. some are, but most are used with a lever motion that results in a mixed push/draw cut or at an angle.

[@stroppystuff641]

So what type of finish would you put on plane ?

[@verdigrissirgidrev4152]

​@@stroppystuff641 400-600 for rough work or hard wood were I'll have to resharpen often, 1500-2000ish for finisher planes. I have some coticules too but rarely use them anymore, the trick is to use very low pressure on the stones a la Cliff Stamp.

[@stroppystuff641]

@@verdigrissirgidrev4152 if the trick is to use low pressure in order to simulate the properties of a finer stone, why not just use a finer stone? As shown by Todd, it is literally impossible to deburr on a coarse stone. There will always be fragments outside of the sharpening triangle.

[@verdigrissirgidrev4152]

@@stroppystuff641 I could ask the same question in reverse. as the same technique can be used with fine stones, the nominal grit isn't the same as the effective one (i.e. entry depth). you could theoretically run into an issue were the stone doesn't cut due to lack of pressure, but that is unlikely to happen in the quoted range, especially with SiC and it's less of an issue in general when apexing because the pressure per area is higher.

[@stroppystuff641]

@@verdigrissirgidrev4152 because it's proven that it's impossible to deburr all burr fragments outside of the sharpening triangle without progressing to finer abrasives. Go check science of sharp