wickededge wrote:


Clay,

I have been meaning to ask, 1.) what steel is this that you were using for these tests, and 2.) what RC? Just curious ... thanks

cbwx34 wrote:


well, not sure if you mean the time to build a jig (if you have standard hand tools then should be just an afternoon or two..) or the time to test a blade. I timed myself doing a 'full map testing session' and it took me about 20 minutes. There is a description in the directions on how to do a 'fast test' and you can easily cut that time in half. The results won't be quite as accurate, but it will certainly 'ball park' you.

For those of you that might have interest in the 'sharpness tester jig' website, I have just posted updates to that site that include:

a new PDF Library of User Submitted Data:
/howsharpisit.com/PDF_Database

Video Library updates:
Beam_Balance_Basics_Part_1 (1:43)
Beam_Balance_Basics_Part_2 (2;50)
Cut_Test_Procedure_Basics (6:54)

and:
Excel Templates updated as of 9/2/2012, Make Sure You Are Using The Latest UpDate for data crunching!

-Dan

FredHermann wrote:


Oh, man,.. you are prying open the lid on pandoras' box.. last time I got near this subject the topic ran on for days.. see: "question with a sebenza.."

Although there are many knowledgable "steel junkies" that hang around this forum, i would suggest you also cross post your above "curious" to Cliff at: the towards .1 micron Forum..

PhilipPasteur wrote:


For what it is worth I would suggest that you get the genuine Dino-Lite /Veho or better. I had a bad experience with trying to save a buck going the route that Phil suggested above, and just wasted time and money trying to out-smart myself.. Optics are funny that way, you *do* have to pay for what you get.

Sharpness Testing is a little discussed subject, oddly enough, here on this forum. I thought I would copy over a post or two where that subject has come up. Also it is a way of introducing the website that contains information about a "hobby project" sharpness tester that you can build yourself.


WayneReimer wrote:
..
This is a clear demonstration that the long relied on "fingertip test" is not worth much. .. I'll keep everyone posted on how it stands up


I think what you might be saying is that testing a knife for sharpness in a reliable way can tell you a lot.. there is valuable information to be gained in assessing your sharpening methods when you start asking How Sharp Is It, and you are able to find the real and reliable answers to that question. If you are interested in blade testing on the hobby level you might want to drop by : www.howsharpisit.com/


wickededge wrote:
BLD - I'm about halfway through reading the new site. It looks terrific. Thank you for sharing with with everyone here. I can't wait to build one and add it to the testing I'm doing.


Well, Clay there are two ways to skin the cat, as you know. One is to do actual mechanical tests on the blade like CATRA and "the Jig hobby project".. the other way is to do what you are up to with the 800x scope, that is, just *look* at the apex and see what you can see.. actually your way has a lot to recommend it.

Of course the whole subject (of sharpness testing) can be argued/ explained/ discussed on and on/ for many days and many pages in a forum, and we certainly do not want to get near that right now, but one thing that your optical system can *not* do is return to you numbers, except for the reference scale nano-meters numbers. If you have a mechanical tester that returns numbers then you can get output like this from our latest excel spread number crunchers. Who knows if they mean anything, but they are sure fun to look at: www.howsharpisit.com/Elmax_ZT0560_Map.pdf

WayneNicklin wrote:


huh?

wickededge wrote:


Well, Clay there are two ways to skin the cat, as you know. One is to do actual mechanical tests on the blade like CATRA and "the Jig hobby project".. the other way is to do what you are up to with the 800x scope, that is, just *look* at the apex and see what you can see.. actually your way has a lot to recommend it.

Of course the whole subject (of sharpness testing) can be argued/ explained/ discussed on and on/ for many days and many pages in a forum, and we certainly do not want to get near that right now, but one thing that your optical system can *not* do is return to you numbers, except for the reference scale nano-meters numbers. If you have a mechanical tester that returns numbers then you can get output like this from our latest excel spread number crunchers. Who knows if they mean anything, but they are sure fun to look at: http://www.howsharpisit.com/Elmax_ZT0560_Map.pdf

WayneReimer wrote:


I think what you might be saying is that testing a knife for sharpness in a reliable way can tell you a lot.. there is valuable information to be gained in assessing your sharpening methods when you start asking How Sharp Is It, and you are able to find the real and reliable answers to that question. If you are interested in blade testing on the hobby level you might want to drop by : http://www.howsharpisit.com/

mark76 wrote:


Well I can't imagine what the problem is there. Of all my newer 'particle steel' knives I like Elmax and the way ZT handled the treatment of the steel the very best of all of them. I guess we all have our problem knives, for me it is the sebbie.

Anyway your comment above made me drag out my pocket carry 0560 and see how sharp it is after a week of on and off duty of doing the usual for me that include everything from trimming a rib-eye on the grill to opening the occasion box. You can see from the chart below that the heel is getting duller thru this use, but portions of the curve of the knife are still at shaving sharp, reading numbers as low as 140g, which is within 20g of a reference double edge razor blade. I know for a fact that I can get my example of the ZT0560 to a flat 170 Apex push Cut sharpness all the way across the blade using a WEP. That is easily sharp enough to shave with. I can not comment on the 'comfort shave factor' as I never really tried to actually shave with it, I just am reading the numbers..


above Chart/ data generated by: HowSharpIsIt.com

Here is a picture of the Out of Box factory Edge on the ZT0560: It takes some work, of course, on your WEP to get this to the 'shave point'

CliffStamp wrote:


I have tested utility knives like what you find sold as 'utility knife replacement blades' at Home Depot and True Value hardware under brand names like "Stanley" and "Irwin" but they are just very dull, usually baseline numbers in the 350-400g. The Gillette type double edge replacement blades in the pharmacy are much more like what you would want as a reference, as they are consistent and very sharp across their entire length. I do not have access to 'straight razors' so, sorry to say, can not test them

The following chart is an example of results from a generic double edge razor sold by the Rite-Aid pharmacy chain stores. This data is simply sorted low to high, not put thru a proper data cruncher, but I thought I would present it this way as an easy way for 'laymen' to get the gist of it. (throw out the lows and the highs!)



Note: low numbers= sharper, high numbers= duller

CliffStamp wrote:


This is interesting, and I will put this on the 'to-do'list. I was looking through my stack of testing that I have done with the jig and came across one early on that was done with the ZT and the baseline numbers started as low as 175g so I know that I can get at least that far with it. It would be interesting to see if that could be brought even lower, and if the sebbie could be brought along with it. It would be interesting to see if I could 'find the bottom' (so to speak..), but with S35vn I don't think I have the equipment or the skill here to really find out the answer to that, but it would make an interesting afternoon of sharpening I do know that I have found such "bottoms" with certain knife steels: for example I tried pushing a CRKT M16 every finer and found out that the jig told me I could never (no matter what I did!) get it sharper than 180 or thereabouts. CRKT says the alloy is 8Cr15MoV.

cbwx34 wrote:


Well, I am going to return them both to pocket carry over the next week then re-test them both. But it is probably clear that there have been some zealous overstatements that have been made prior to the testing Cliff had an interesting series of posts once about how knife ergonometrics can effect "apparent sharpness feedback" to the user. i think we need to find those comments and re-post them somewhere..

cbwx34 wrote:


that is still a rather sharp knife, it will easily shave arm hair, it will not direct push cut tomateo skin, but will cleanly slice a tomateo using an easy draw cut under the weight of the blade, it will still 90 push cut copy paper if you handle it carefully and keep the finger hold on the copy paper within 1/4 to 3/8" of the blade contact. -Will work on getting a parts list together this weekend. the thing is so simple you can basically figure it out from the videos and the posted pictures. The part of it that necessary to understand more fully is the proper placement and use of the testing media, how to run a 'test series' properly, the nature of the whole concept of "testing sharpness", and a few other details that we need to put in some sort of documentation sheet. The whole thing is still a work in progress. .. Cliff has been very kind to work out an Excel template that crunches the numbers. From a recent email to Cliff, here is how I feel about it so far:

... I am not yet confidant enough in the 'testing jig' to accept it as a tool to measure anything but gross ranges of data. In fact because of what it is, and how it is built, it probably has limits that must be "respected" (if that is the right turn of phrase -grin!-)..

I feel an acceptable level of comfort with it as a rough gauging tool, within 20 grams push cut increments starting from commercial razor blades thru a range to kitchen knives, in that range I feel it is testing well, and the data it is returning is meaningful for that use and can be relied upon. When we are taking about testing subtle variations on very sharp high end blades with subtle variations in sharpening technique, well then, ... humm not so sure.

CliffStamp wrote:


ain't it the truth!

Well here are some 'un-biased numbers'... I have sent this data to Cliff, who will 'crunch it' and make his own comments later.. he knows what numbers really mean, I am just a hacker, but here is my following take on the situation so far:

The ZT steels performed almost identical to the sebbie.. The basis sharpness was a little worse (higher numbers mean less sharp) than the sebbie (I think just because my 'dressing' of the blade before the test was a little hurried..) . Also per cbwx34 I re-ran the ZT through the 10 slices of copy paper. It, again, performed much like (actually exactly like!) the sebbie: i.e. after 10-15 cuts it started to fail on the 90 pushes, then I put it back on the test jig and noted the following numbers from random points along the blade: 352; 362; 344; 342; 346; 370. This is just like the sebbies numbers after the paper cutting, in other words about a 100 gram jump from baseline numbers after sharpening:

you can get the xls raw data here or just look at the following chart:



for those of you that want to see how all this stuff was collected, here is a shot of the 'test-bench'. You can build yourself your own test jig for under $50 bucks and settle all those arguments at the local beer-bar about whose blade is sharper than yours:

CliffStamp wrote:


Thanks Cliff for the above explaination. I will have time today to continue my experimentationswith the ZT and may be able to re-polish the sebbie. I have equip here to take a blade only to 0.25u , and anyway I am not nearly as good at those efforts (or near as fast!) as Clay, who can polish a blade faster than you can say ready-set-go much finer than that!

I find it kind of interesting that you are sort saying, 'well lets be careful about putting too much on the shoulders of the physics of the steel, because we can not really account for the RC (and other differences of the material) to give us these extreme user reports. I understand your cautions here, and cbwx34 has issued cautions in the same vein, they are duly noted and I understand what you are all saying there.

--> However, I note that you are a 'knife steel junkie'. I see your posts about the perfomance of certain blades, I note that you recently began testing a DiamondBlade knife that uses a very sophisticated ultra high pressure forging and hardening technique to form the edge that takes the RC to +68. User reports claim 3x and 4x increase in blade life when doing field work with that knife. I pose the hypothechical: If you could have a sebbie with CBN pressure forged blade made by DiamondBlade would you not instantly grab it from my hand or would I hear you say, well "No, thanks anyway Dan keep your hybrid there, i am fully satisfied that I would only get at most a +5% increase in performance on that.."

I need to clarify something about my use of the term 3x 4x. I am not using that term about the steels engineering specification: I am using it the same way DiamondBlades is using it in their advertising and product information. How we are using that term means (to use an example from DB..) "I can skin three wild boars with this blade vrs only one with Brand XYZ blade, so my DB is outperforming that blade by 3x." I am *not* saying that the engineering metals specification has gone up by 3x. For myself, I do not skin wild boars, but do carry a pocket EDC thru a fairly steady daily routine. I notice that the sebbie makes it (sometimes) thru the end of the day before I find myself looking around for a handy hone ( I tend to use a Sypderco UF beach stone that I keep in my kitchen for that...), but when I ave the ZT it might take three or four days (or sometimes more!) before I even think about dressing it. I understand that it is just all very 'seat of the pants', but oh well...

CliffStamp wrote:


Well, darn the luck I just got home very late and did not get to the ZT testing, but will for sure do it and post results tomorrow..

I know very little about steel from a material science point of view, but do I understand what you are saying here?

Is your use of the term "strength" the same term I am thinking of in this discussion here, my term is more like: "wear resistance in normal use" (wear resistance to me would include a range of factors including deformation or plasticity if the blade edge was side cut or 'torqued' against a load, abrasion resistance to hard materials, etc etc..) anyway my question is what you are saying is that wear resistance is liner related to the RC hardness scale?

I thought the effect was more logarithmic and therefore the factor becomes very significant across the range of say: 56RC to 61RC. I did not pick those numbers out of the air, as Reeve states that when they began the use of Crucible steels at their shop (around 2002 ?) they chose 56, in sharp contrast to Phil Wilson who was working with Crucible and responsible for a lot of the development and stated optimal RC to be targeted to 61. So there is a big range there. Is it just linear, is that correct? If I have a 56RC then I have to make it test RC 112 to double its wear resistance??

cbwx34 wrote:


The answer is because Ribs knife is a member of a set.

Well, it's the old problem: If you don't ask the right question you will get the wrong answer every time. In this case you have phrased the question (and it looks like maybe Cliff did as well..) to inquire specifically about a single member of and one occurrence in a subset of a much larger set. By phrasing any question that way it forces the answer to include the member of the subset to then become part of the answers equation. The question, properly phrased in relation to the largest set of which all are members of is: “Why are there so many reports of issues with the CRK sebenza failing to properly hold or take an edge that is equivalent to other similar knives made with the same steel?” If you ask the question like this “Why did Joe or John or Harry have trouble with the CRK sebenza failing to properly hold or take an edge that is equivalent to other similar knives made with the same steel?” then, of course Joe, John and Harry become part of the answer, when in fact they are not.

Forensic science battles with this all the time, all science does in fact. In this brief topic thread you have 3 separate reports (the Joe John and Harry’s of this case..) of trouble with the knife in question. If you look at the larger sets as seen on, for example, Blade Forums, Knife Forums, etc you will see hundreds of trouble reports that comprise a very large set group..

Anyway, I did as you requested, I cut 10 slices of copy paper with the sebbie, and then it began to fail to direct push cut at 90. I put it on the test jig and took a sampling of points across the blade and the numbers have jumped to 350-375 grams from un disturbed locations that were in the low to mid 200s. I will repeat all this on the ZT0550 as soon as I get a chance, hopefully that will be today, but only so many hours in the day for me .

BassLakeDan wrote:


since I stated the above, it seemed like a good idea if I could 'test" my empirical observation about different knife makers results with that steel. Today I sharpened my sebbie with my usual routine for that knife (19deg with a finish of 5u) then put it on a knife test jig to measure a sample of push cuts. Usually the data is collected on this jig across equal distant points across the total blade length. But for this test I repeatedly re-set the jig to land on the same approximate area every 5 test stokes. The idea on that is that the testing, is by nature, semi destructive to the apex edge as the jig contacts the same area repeatedly. Perhaps this would give a clue about what seems to be a “soft” steel on the sebbie. I will repeat this test tomorrow with a ZT0550 which is the same steel, but is much more durable in EDC use.

FYI, the sebbie turned in a very solid performance here, and although after 75 contacts the push cut force went up abt 100 grams, I consider that very good. For your reference you can see that the sebbie started the test sequence in the area at about and just above 200 grams. That is a very sharp knife for EDC use, as a commercial razor blade will test out at about 120 grams to start.

I make one conclusion so far about all this: 1.) I think we might have debunked here the ‘must be operator error and you have a wire hair remaining on the blade apex’ issue.. I conclude that the thing would have never survived 75 contacts in the same area and only shown a 100 gram increase if there were serious apex issues with sharpening technique. It seems likely that things would have degraded much more rapidly and the push cut forces would have ramped up to much higher values much sooner if that was the case

Keep in mind: It is important to note that push cut apex testing reveals only very limited information about real world “cutting ability”.. No matter what the results of my testing tomorrow of the ZT0550 I stand by my statement that the ZT holds up 4x better than a sebbie in the real world.

(Warning!) Anecdotal irrelevancies follow: a.) There are many reports of owners returning a sebbie to ‘the factory’ for resharmening, only to find to their horror that the blade has been run through a commercial fast cutting jig and suffered as much as a 2mm ‘shave away’ of blade length/ and height. b.) Chris Reeve has been quoted as saying ‘ I like to keep the blades soft so the are ‘easy to sharpen” d.) the knives are know to be a so-called mid-tech product, a term which is widely accepted to mean ‘out-source critical components’, in this case steel hardening, tempering, and so forth. e.) I personally micro graphed my sebbie on arrival (out of box) and noted one of the most crappy factory applied sharpening jobs I have ever seen on a +$300 edge. The edge angles and depth were all over the ball-park and the grit looked about-300 incompetently applied from a wheel that was obviously in need of immediate maintenance

link to raw data here..



link to raw data here..

... ..
well, of course, this is not what you guys really have in mind, but I did rig this up out of some old steel foundation straps.. Doesn't work too bad for resharpening your old utility box knifes ! Actually, I was working on this blade for a reason, and if it goes well I will fill in the missing details later.