Spyderco Delica ZDP-189 : edge retention on polypropylene (CBN vs medium rods) 

Yes, and another thing I failed to mention is that the Delica allows a much longer draw while the much shorter Stanley blade concentrates the force on a smaller area. In general draw cuts reduce force and gain control which also will lessen deformation/chip damage. Ironically if the material is clean you are more likely to run into problems with edge retention due to the edge being strained/fractured because if ropes are clean they have a very low rate of wear and you are back to then doing hundreds (if not thousands) of cuts. The other thing is the more cuts you do the more likely you will do them not well, hit something, etc. and again you now have an edge which was not worn away but chipped/fractured. Ironic and maybe amusing that dirty materials like carpet when cut produce the most inherently stable edges when sharpening (unless you cut the edge off in which case it doesn't matter what was cut as all steel which was effected is gone anyway).

Cliff Stamp More good info. Thank you.

As do I. It is faster if you just make things up, a lot of people go that route. But this channel is about making baby jesus smile so we doesn't afraid to do a little work to make a little science and learn a little along the way.

The problem with making things up - let me simplify - the proof is in the pudding. I refuse to drink the kool aid.

You're a crystal lite guy are you then?

Tang

Tapered?

Yes that is an excellent question, how much of a difference would be seen if this was m390 for example. I am going to explore this as I get various cutting media. Indeed. Too often people make statements about edge retention which it is just jibberish because it isn't meaningful because it is so strongly varied as you have noted.

Greg, how much force were you using? When you say reprofiling do you mean altering the edge angle? How much of an angle change? Were you using a lubricant/fluid? The diamond stones have a near identical grit and produce a near identical finish. I can't see a difference even under 150X linear magnification nor can I measure it with sharpness measurements as precise as 5%. However there may be a long term durability advantage to CBN vs diamond due to diffusion based wear in diamond however that is just a hypothesis. I have no data and I have seen none. But this is a critical factor in industrial application as diamond isn't used on steels for that manner. But they grind much hotter that we do by hand.

I haven't been able to measure the actual force, but I was basically just letting the weight of the knife + just a tiny side pressure to keep the blade straight. The knives in question were the Delica & Caly3 (both ZDP), and I used the 30-degree setting dry (no lube). I also did a Benchmade in S90v, but have no idea what it's starting angle was before I got it @ 30. The stones just feel really smooth already, but hopefully I just knocked off the excess particles?

Greg Fowler Greg, this is one of the difficulties with talking about plate abrasives as it isn't trivial for me to tell you how I use them because unless you are going to use a force plate under them (no one does) then it comes down to feel. Here is the best I can tell you, under no circumstances should you be knocking pieces off, if you are then you are using far too much force as the abrasive should wear down not be torn off. I don't even use the full weight of the knife initially. I have done far more sharpening than what you have noted and the rods still cut well. The key is use just enough force for them to cut and this is really light and ideally you have to use a lubricant, a thin one.

Cliff Stamp Ok, I guess I didn't mean to say that any grit particles were noticeably coming off the substrate - just that perhaps the rods ship with excess non-bound abrasive and that it is "normal" for that to go away (like you'll notice on the inside of the hollow rods, there's a lot of loose useless grit stuck to it from the coating process). So, I don't think that the abrasive was ripping out of the binder. I never felt/saw any sand-like particles actually pop off. It's just the texture of the rods is much smoother already and I wasn't hearing the same pleasant "scrriiitchhh" sound. Also, the scratches seem less pronounced on the edge surface. I have yet to try them again on a more reasonable steel (e.g.: VG-10), so maybe they are still effective at least for the softer/easier non-tool steels. By "force plate", do you just mean a simple postal-like scale or do you mean something more extravagant with a load-cell and whatnot? And one more thing to add - I gave up on all my other more-traditional stones (several synthetic Nortons, some cheap diamond-backed steels, Arkansas stones, India stones, etc...), but have just not been having much success with the Sharpmaker. I was hoping for something close to a zero grind with no microbevel, but in desperation after I spend a long time going thru all the grits (CBN --> Medium --> Fine --> Ultrafine) @ 30-degrees, if I just do several passes with only the Ultrafine on the shallower 40-degree setting, I am finally able to shave hairs and slice through yellowpages. The big question though - is how long this edge will hold using this method...? Also, I suck at stropping. I hope it's just that the cheapo chinese 2-sided paddle strop I got is worn. I'm trying to investigate better options (including this interesting, but perhaps gimmicky "Washboard Sharpener": www.washboardsharpening.com/user-guide.html) For as much as I think I know about steel and mechanics (have an M.S. in Mechanical Engineering), it's clear that there are tomes of knowledge I am still missing. Which is why I appreciate all the comprehensive quantitative work you do backed with qualitative reflection. Aside from several very ignorant, annoying people, one of the greatest things about the knife community is how helpful everybody is and how we are all striving to both learn & teach about all aspects of our hobby/collections. Thanks, G.

Greg Fowler Greg, any way to measure the force, if you have load cells you can get the force/time response curve which is interesting and actually use it to train as a biofeedback response. The main point I was making though is that while I know what 5-10 grams feels like as I measure it, it isn't going to mean much to anyone else because they are not and thus one of the big issues I have in communication is exactly that problem of how much force to use on stones. This is compounded by the fact that it isn't even the force which is relevant by the pressure. If you are sharpening just on a micro-bevel your contact area can be as small as on the order of 10 microns thus the pressure skyrockets over when you are working on the actual edge bevel which is on the order of 1000 microns, a 100 times bigger. Thus using even 5 grams on the micro bevel is like using a full pound on the main bevel. This is why when I approach the edge or use a micro-bevel I wet the stones and use just enough force to maintain contact. I show this in one of the Sharpmaker videos and you can see the main issue I am having is just getting the knife to evenly make contact as the force is so low. Now of course the only reason you have to do this is that the CBN rods are a single layer of abrasive unlike the medium rods which are a solid sintered block. Even if you do wear the medium rods smooth just buy a cheap piece of coarse diamond sandpaper, some loose diamond grit and just lap the surface back. It would take maybe $0.50 worth of abrasive to restore the surface. But once the CBN wears down then - well it is worn down. This is why I advocate only using one side when you start, number all the sides and rotate them as they wear. You then use the most worn sides for the very high pressure work (micro-bevel) and use the least worn sides for the low pressure work (the shaping). The edge should easily dry shave your arm right off the CBN stones, if it does not then there are three main reasons : -the edge isn't actually forming an apex -far too much force is being used and the edge is fracturing -there is an edge bias (it has folded over to one side) There are other possibilities but those are the main three.

I don't need a suit.

I would be interested to know what you find.

He has become aware that gender exists and is exploring the consequences of such. The same tends to happen in people in the late teens and it tends to be a few years (if ever) before they snap out of it.

The CBN is more coarse and like a coarse saw has much more material needed to be worn away and thus will stay sharper longer on slicing on abrasive material. If the material is hard and not abrasive this doesn't happen because the teeth can crack off vs being worn down, hence the difference results on the plastic and wood cutting.

Cliff Stamp Thanks, I was wondering something else and I know it is well within the realm of wacky, but I think it is related in a way (kind of) and what I am wondering is, if a toothy edge, which essentially has microscopic saw teeth, were used to cut up food like steak, do the micro teeth get broken off into the meat and then we end up consuming them? Now, I know they are very small, and (probably/hopefully) these remain within the meat and pass out of us. Assuming that a high carbon steel is used vs a type that is corrosion resistant, would there be less likelihood of it harming the body if they were more likely to corrode quickly? (Hey, I did preface that it was going to be a wacky question! :) )

traderjoes Yes you will eat some amount of steel, however you are going to eat much more metal from cooking with metal pots due to the time and temperature of exposure. If you wanted a real concern it would be eating aluminum (from foil) and the extremely non-healthy coatings that are on non-stick pans.

Newfoundland.

They are 0.5 cm increments. They let me cut to specific draw lengths.

In regards to some kind of performance comparison? Yes that is absolutely true, trying to say if someone or something thing is better if there are a number of things changing is very difficult. Far too often something is attributed to steel or hardening when it is nothing more than how they were sharpened/ground.

I am not sure what you mean as the first sentence isn't clear.

Well that was one of the more impressive posts I have made.

I am not sure exactly what you mean, is it why the medium rods hover around the 60%? The sharpness in these is fairly low (for me) because they are severely time constrained, I only have 24 pps to grind off all damage, actually sharpen, and burr minimize. I could double it with a little more time. But the relative sharpness would increase with both blades, the ratios would similar.

As an example you show the sharpness for m3 at 100. A few months ago you doubled your sharpness measurement as you kept exceeding it with one of kyleys knives. Have you once again met or begun to exceed the optimal sharpness measurement.

mark a Yes, I can surpass that now readily in regards to slicing sharpness which is more sensitive (variable). Most people don't do a very good job on that at all but that is mainly because of the buffer/strop over use. I should note the absolute sharpness level being used in these charts even for reference/consistency. Thanks for bringing that up.

I am not sure what aspect of the performance you are referring to.

That high carbide steel at low edge angles is optimally used with a coarse edge.

Bill22252 Bill if you had asked me that even a few years back I would have said yes without much consideration. However as of lately I have seen some data that doesn't support this well. At very high carbide levels steels start to behave like ceramics which in general are not promoted to work well with coarse edges or even take them well. I need to do more work with steels like 121REX however it may be that like most things there is a sweet spot for coarse edges and too high a carbide volume makes them unstable.

Interesting. This video seemed unusual in the sense that you seemed to be making positive statements about high carbide steel.

Bill22252 I have been using high carbide steels for a long time. I have an original 10V "prototype" from Phil Wilson. I just don't think they are the universal solution which is often promoted. Where they work well is cutting abrasive materials with low force and you have decent cutting abrasives and a very thin grind to minimize required grinding and force in cutting.

My beard is nearsighted.