Edge Sharpness Tester

[Ankerson]

.006"? What's the overall stock thickness?

.124" to .014" at the tip.

3 1/8" blade.

 

[KennyB]

.124" to .014" at the tip.

3 1/8" blade.

Ahh that's easier to visualize then. Yeah the only knife I have that nears that thin was my "Needs Work" since it was about .015-.020" thick at the spine up at the tip. Honestly though at that scale, it's hard to really find the "shoulder" and take a square measurement so I never did figure out the edge thickness but it was basically a glorified razor blade.

 

[Ankerson]

Ahh that's easier to visualize then. Yeah the only knife I have that nears that thin was my "Needs Work" since it was about .015-.020" thick at the spine up at the tip. Honestly though at that scale, it's hard to really find the "shoulder" and take a square measurement so I never did figure out the edge thickness but it was basically a glorified razor blade.

It's thick compared to some of the knives I have ran.

 

[KennyB]

I plan on testing my Kershaw "Wild Turkey", Leek and my SAK first since they have the thinnest blades. Hoping the 3/16" thick Izulas fit too.

If only I hadn't lost the "Needs Work" Seriously, if you're familiar with the Leek, its tip was even thinner than that.

 

[Ankerson]

I plan on testing my Kershaw "Wild Turkey", Leek and my SAK first since they have the thinnest blades. Hoping the 3/16" thick Izulas fit too.

SAK's are thin, spine thickness. :thumbup:

 

[Ankerson]

I plan on testing my Kershaw "Wild Turkey", Leek and my SAK first since they have the thinnest blades. Hoping the 3/16" thick Izulas fit too.

If only I hadn't lost the "Needs Work" Seriously, if you're familiar with the Leek, its tip was even thinner than that.

Yeah, I had a Leek here about 4 years ago.

 

[grizzled gizzard]

Awesome haha!

edit: Are you guys stropping your knives at all before testing after they come off of the stones or trying it straight off of the stone? Can you test both ways and post up results?

Stropping on leather with 1um poly-diamond works well for belt sharpened knives. I get much more consistent measurements with significantly lower average.

My 52100 blades with a normal shop finish of 8um CBN on a leather 1x42 belt were running an average of 106, but with a standard deviation of nearly 40 grams.

After stropping 15-20 strokes the average went down to 64 and the deviation went down to single digits.

On blades sharpened on stones the difference wasn't significant.

I haven't done any testing of EP or WEPS edges yet, but I'm looking forward to it.

 

[REK Knives]

Ok I can't really figure out what's going on... going to call Mike tomorrow. I would love to see this looked at by someone like ToddS w/ an SEM to make sense of the different readings, maybe I'll send him mine if he has time =)

On all of the progression below I am finishing with edge leading whisper light passes (except for the strops of course, those are edge trailing).

200 grit, edge leading alternate passes - avg. 75 BESS score

Same edge, now stropped on pant leg - avg. 40 BESS score

1k grit edge, edge leading alternate passes - 55-150 BESS score (all over the place - probably wire edge?)

1k grit edge, edge leading alternate passes, stropped on pant leg - 35 BESS score

3um lapping film, edge leading alternate passes for the micro bevel, hair whittling - 90 BESS

3um lapping film, stropped on .25 diamond on balsa, edge trailing alternating passes, passing HHT-4 all points of edge - 110 BESS

Knife tested:

What I don't understand is how I was getting a lower BESS score on a 200 grit diamond edge than the 3um stropped edge... Especially when the 200 grit edge would barely kinda shave arm hair and the 3um edge would sever free hanging hair. pretty confused right now! :concern:

 

[KennyB]

Ok I can't really figure out what's going on... going to call Mike tomorrow. I would love to see this looked at by someone like ToddS w/ an SEM to make sense of the different readings, maybe I'll send him mine if he has time =)

On all of the progression below I am finishing with edge leading whisper light passes (except for the strops of course, those are edge trailing).

200 grit, edge leading alternate passes - avg. 75 BESS score

Same edge, now stropped on pant leg - avg. 40 BESS score

1k grit edge, edge leading alternate passes - 55-150 BESS score (all over the place - probably wire edge?)

1k grit edge, edge leading alternate passes, stropped on pant leg - 35 BESS score

3um lapping film, edge leading alternate passes for the micro bevel, hair whittling - 90 BESS

3um lapping film, stropped on .25 diamond on balsa, edge trailing alternating passes, passing HHT-4 all points of edge - 110 BESS

Knife tested:

What I don't understand is how I was getting a lower BESS score on a 200 grit diamond edge than the 3um stropped edge... Especially when the 200 grit edge would barely kinda shave arm hair and the 3um edge would sever free hanging hair. pretty confused right now! :concern:

I think I can actually make out the wire in this image https://lh3.googleusercontent.com/-...AAC_c/X3eFl_HFa5A/s800/20150516_193607842.png

 

[Komitadjie]

That IS an interesting bit of data, Josh... I wonder if the extremely large "teeth" resulting from the coarser stone were causing pressure points that would sever the test media more easily? If it's truly a "cleaving" behaviour instead of push cutting through, that might do it? It certainly seems interesting that the final edge there would score up into the range of hundreds, I would have expected it to be very, very low.

Finally got a chance to start some testing today! Nothing terribly serious, but a good opportunity to play with the machine a bit, and get a baseline for some sharpening to be done tomorrow. Here's my test unit, all set up and ready to roll!

The brass head nuts have been removed, and replaced with the plastic ones to reduce the weight for the first experiment, I was hoping to be able to confirm the "zero" point as the point where a razor blade would sever the test media.

The test head loaded with media, I have laid the unit on its side for this picture, to give a slightly better lighting angle.

Set up and ready to go with one of the provided razor blades! For this picture, I lowered the head until the test media just barely touched, then locked the ram to take this picture. The media was then cut by application of my thumb to the top of the ram, and discarded, so that the following test would not be flawed.

Unfortunately, I was not able to confirm the zero point adequately by the blade method, the test fiber was severing instantly under even the reduced weight on the ram, so I reverted to the suggested test method in the user's manual, and placed my scale under the ram to confirm down-pressure. The brass nuts have been replaced on the head, and the reading of 49.7g matches up nicely with the listed 50g nominal. With this confirmation, I judged that my unit was within calibration, and ready to begin testing!

For my first test, I chose the same BRKT Northstar EDC that was shown in the photos last night. I've been using this one heavily to break down cardboard boxes, so I chose to run two different test series on this knife. One at the spot of the belly that was easily feel-able as quite dull on my thumb, then a second time near the grip where it felt distinctly "sharper."

The "duller" section in the belly yielded about the number range I was expecting, with three tests showing:

#1 = 322.6
#2 = 320.9
#3 = 317.1
AVG = 320.2

The "sharper" section did indeed test considerably sharper:

#1 = 128.2
#2 = 138.8
#3 = 154.0
AVG = 140.3


Moving on, I installed my second test choice in the unit, my Spyderco Para 2 in M390. This blade is one of my nicer edge-holders, and is still what I'd consider "decently sharp" for everyday carry. Since I had not been working it particularly hard, I decided to stick with just one test series for the knife, for the moment.

#1 = 93.3
#2 = 59.1 - This point I discarded, I am 99% sure I bumped the rim of the test media cup with the rim of the other cup I was using to sift the media in with.
#3 = 93.5
#4 = 93.6
AVG = 93.5

I was absolutely STUNNED at the repeatability of this one! I am going to run this series again tomorrow, I think, just to confirm it.


You can see my ultra-high-tech data recording method here! Only the finest of scrap paper pulled from the garbage. My good note pads are still somewhere in my horrific moving mess.

And the raw data! ... Ok, yeah, I might just be grinning about my 7D and speedlight now. Did I mention that the one little fluorescent light you can see in the pictures is the only light source in the room aside from the on-camera speedlight?

 

[Jason B.]

Josh,

I see burr present on the edge and in photo #2 you can see how it has stood straight after being stropped on a pant leg.

You should be able to get the edges a bit cleaner using diamonds, do you do any distressing of the edge? Cork, soft wood, felt block?

 

[Ankerson]

Ran what I call my box cutter, hasn't been sharpened in awhile, still sharp though, I use it to open packages and whatever else is needed for the most part at home.

ZAPP A11, 400 grit, 15 DPS.

127, 130, 121, 129

126.7 ave.

 

[HeavyHanded]

Ok I can't really figure out what's going on... going to call Mike tomorrow. I would love to see this looked at by someone like ToddS w/ an SEM to make sense of the different readings, maybe I'll send him mine if he has time =)

On all of the progression below I am finishing with edge leading whisper light passes (except for the strops of course, those are edge trailing).

200 grit, edge leading alternate passes - avg. 75 BESS score

Same edge, now stropped on pant leg - avg. 40 BESS score

1k grit edge, edge leading alternate passes - 55-150 BESS score (all over the place - probably wire edge?)

1k grit edge, edge leading alternate passes, stropped on pant leg - 35 BESS score

3um lapping film, edge leading alternate passes for the micro bevel, hair whittling - 90 BESS

3um lapping film, stropped on .25 diamond on balsa, edge trailing alternating passes, passing HHT-4 all points of edge - 110 BESS

Knife tested:

What I don't understand is how I was getting a lower BESS score on a 200 grit diamond edge than the 3um stropped edge... Especially when the 200 grit edge would barely kinda shave arm hair and the 3um edge would sever free hanging hair. pretty confused right now! :concern:

Also looks like D2 or other high carbide size steel. That could be throwing off the results somewhat, but still not clear (aside from wire/burr edge) why that would effect the #s - especially if other test media show a steady increase in pressure cutting. Could be higher refinement but with some micro rounding that shows in the test media and not on hair?

 

[Twindog]

Are you testers able to hold the string tension of the cutting medium constant?

 

[Ankerson]

Are you testers able to hold the string tension of the cutting medium constant?

Takes some getting used to, but the way it's set up (Designed) it's not all that hard to get consistent.

 

[Komitadjie]

I have not been having significant difficulty with it, I just pull it "more or less snug" with my fingertips as I tighten the second clamping screw. From the repeatability of the results I'm getting and the low standard deviations, I think it's not a problem for me, anyway.

 

[Ankerson]

I have not been having significant difficulty with it, I just pull it "more or less snug" with my fingertips as I tighten the second clamping screw. From the repeatability of the results I'm getting and the low standard deviations, I think it's not a problem for me, anyway.

Same thing I do. :thumbup:

 

[REK Knives]

Josh,

I see burr present on the edge and in photo #2 you can see how it has stood straight after being stropped on a pant leg.

You should be able to get the edges a bit cleaner using diamonds, do you do any distressing of the edge? Cork, soft wood, felt block?

Yes I destress pretty much all the edges I work on... No I don't use cork or wood or anything to deburr, just edge leading passes with extremely light pressure alternating sides every pass. I suppose stropping on leather + compound would ensure any wire edge was gone, but then you kind of loose the nice teeth unless you don't use leather.

Also looks like D2 or other high carbide size steel. That could be throwing off the results somewhat, but still not clear (aside from wire/burr edge) why that would effect the #s - especially if other test media show a steady increase in pressure cutting. Could be higher refinement but with some micro rounding that shows in the test media and not on hair?

Yeah I'm stumped right now... it could be as Dan pointed out above, Clay Allison had pointed out years ago when a similar sharpening jig was built that the peaks of the micro serrations could sever media faster than a highly polished edge.

 

[Jason B.]

I was viewing from my phone earlier, it's much less burr than I thought, shouldn't skew results that much.

Although, in the last picture you can kinda see some 1k scratches at the apex, that could really throw things off.

 

[HeavyHanded]

Yeah I'm stumped right now... it could be as Dan pointed out above, Clay Allison had pointed out years ago when a similar sharpening jig was built that the peaks of the micro serrations could sever media faster than a highly polished edge.

D2 is kind of a strange bird depending on how high the RC has been pushed. An inverted bell curve with the high water mark at 1K jibes with how I prefer to sharpen that steel, but is still mysterious that it responded with a pretty definitive drift. Maybe re-run the prep, avoiding the films and strops and just take it as high as possible with stones/plates. When the carbides are that easily seen standing out of the matrix I have to suspect on some level the softer media is dragging it down in some respects (#s began climbing with film usage/carbide excavation).

Edit to add:
Is this exact effect that has me avoiding all but the most superficial stropping on high carbide steels in general and D2 in particular, even with diamonds.