Sharpness Testing Jig

[wickededge]

Some more preliminary results, all at 15 degrees:

Superfine 1600# = 200g
Microfine 0.6um = 185g
14um Strops 10 strokes = 175g
14um Strops 20 strokes = 195g
14um Strops 30 strokes = 220g

These are quick results, not well documented yet as I’m still just getting a feel for the testing methodology, the data collection, the machine etc…

Still, it’s fascinating to see the rapid improvement from just a little light stropping, at a much coarser grit and then see the edge degrade rapidly with additional strokes. What I’ve seen so far gives me some ideas for setting up a few tests to see if this preliminary data holds up and then maybe we can come up with some theories to further test. I already have some educated guesses about the strops but will hold off any judgement until we have enough data to be confident.

-Clay

[Josh]

Definitely following this thread w/ interest!! Nice job btw Clay on the build! I really need to build one myself…

Ok, so who’s going to start the data entry and create some neat looking graphs? lol

So what test media to degrade the edge and test edge retention (in the future of course) will you use Clay? Something that is consistant but not too abrasive…hmmmm

I am really interested in if this will be able to be used at some point in the future to rate the slicing ability of any given edge…

Good work again!! Thanks for investing the time, the Lord knows I don’t have any extra right now lol

[BassLake Dan]

I’m already starting to build some data and seeing some trends. … I also noticed an impressive deterioration in the sharpness with progressive testings, due I imagine to the repeated force applied to the edge in each successive testing. It should be fairly simple to conduct some durability/edge retention tests…

Yes, this is a common observation when one begins testing blades with the jig. Since the jig is very much more sensitive than non numeric testing methods (paper slicing, hair whittling, etc..) it surprises and hits everyone over the head when you see that (and realize) that sharply apexed steel is actually a very very delicate item and deforms and degrades very rapidly with initial use. The slope of the curve of degradation is extremely rapid. Of course, this is counter intuitve, as we build bridges and freeway overpasses out of steel, so in any form it is strong and permanate?, or so we think. All our understanding of steel works for us in everyday life, until we use it at its extreme application: cutting edges where apex edges are measured in microns.

using the scotch tape media to do this type of testing is described in detail on the jig tester site. Excel spreadsheet templates are provided to record and graph this type of testing: http://www.howsharpisit.com/Edge_Retention_Tests/Template_Degradation_Testing.xls

[Leo Barr]

It is interesting to note that extremely low sharpening angles do not retain their sharpness for long.
Yet we know that a descent thinning bevel before the primary cutting bevel makes for a perceptibly keener edge .
What I would be really interesting to see is the effect of compound bevels so a thinning bevel with a fine cutting bevel topped by an acute micro bevel .
I brought this up elsewhere in the forum – Japanese Knife Imports posted a video on this a couple of years ago so what they say some of the top-line Japanese knife manufactures are doing is on top of the normal cutting bevel of 15-16Ëš they are putting a micro-micro bevel nearing 40Ëš on top of this thus beefing up the blade edge whilst retaining the characteristics of the low angle bevel. It seems to make absolute sense to me and it would be interesting to see repeated sharpness tests to either prove or dis-prove this method. I suspect that these Japanese knife manufactures know what they are doing since they are some of the best blade-smiths in the world . It would however be very interesting to see if this holds as an acceptable finishing to maintain an edge for longer. I include a link to the video showing this albeit done on water-stones.

[Mark76]

Really nice job! And very interesting results… Looks like I’ve got a project to do :cheer:

Molecule Polishing: my blog about sharpening with the Wicked Edge

[BassLake Dan]

It is interesting to note that extremely low sharpening angles do not retain their sharpness for long.

From the jig documentation of degradation tests is this chart from CATRA.. You can see how rapid these curves are typically:

[wickededge]

Dan,

My thoughts for testing the degradation came directly from your observations on your site. I am very curious about how your formulas work within the spreadsheet. If you care to share some insight I’d be grateful. I just snapped this photo under the microscope at 800x of the blade I’ve been playing with:

I’ve been using roughly the same spot on the blade for each test so it’s probably exaggerated.

Attachments:

• h9f76a62.jpg

-Clay

[Mark76]

It is interesting to note that extremely low sharpening angles do not retain their sharpness for long.

From the jig documentation of degradation tests is this chart from CATRA.. You can see how rapid these curves are typically:

[/quote]

Interesting chart, Dan. It indeed shows how rapidly edges may loose their sharpness.

However, the chart doesn’t seem to support the quote by Leo. If you compare the two BG42 curves, at places the 20 degree curve goed down even steeper than the 13-16 degree curve and at no point in time the 20 degree edge comes close in sharpness to the 13-16 degree edge.

Molecule Polishing: my blog about sharpening with the Wicked Edge

[BassLake Dan]

However, the chart doesn’t seem to support the quote by Leo. If you compare the two BG42 curves, at places the 20 degree curve goed down even steeper than the 13-16 degree curve and at no point in time the 20 degree edge comes close in sharpness to the 13-16 degree edge.

Mark,

I posted the CATRA chart only to show an example of the log fall off of sharpness thru initial use. It does demostrate that very well. However:

The subject of proper angles, strops, etc, for a given steel or specific use must be approached very carefully and the CATRA test system is suspect and very controversial. The various machines that CATRA designed and markets to the professional industry is the subject of endless debate, and I don’t want to throw gasoline on the fire here in this forum.

Anyway, long story short: I suggest that everyone do their own testing on their own blades and draw their own conclusions in the framework of very specific local tests that you have control over yourself. This was one of the main motivations I had when going forward with the design and construction of the $50 jig. CATRA uses a very contrived abrasive imbedded propriatry test media that is targeted towards the commercial meat cutting and packing house industry. Hardly the kind of thing you and I are doing with our high end Sushi knives !! The test media is inextricably intertwined with the results. There is a discussion of that important consideration on the jig site.

[wickededge]

I made a couple more small additions to the design: I added a second binder clip on the third beam to help add weight in 1 gram increments and I printed a 1mm graph and taped it to the top of the scale so it’s easy to move the blade over for each new measurement. It’s working great. Some more preliminary data, all at 15 degrees:

100# Diamonds = 279g AVG
200# Diamonds = 257g AVG

It’s nice that things are performing as expected so far…

-Clay

[BassLake Dan]

.. I am very curious about how your formulas work within the spreadsheet. If you care to share some insight I’d be grateful.

The formulas are nothing complicated, it very basic statistical math, computing average , means, and determining meaningful variance from the normal. You can use Excel or Open Office and mouse over the cells to see the formulas that the spread sheet is programmed to use for the output to the graphs. If you have a specific question about one of the formulas I will try to answer it if you can not see how it is done from looking at the spreadsheet.

I just snapped this photo under the microscope at 800x of the blade I’ve been playing with:
..I’ve been using roughly the same spot on the blade for each test so it’s probably exaggerated.

Clay,

I really appreciate the photos ! During the original quest for a reliable way to test blade sharpness we had a email round table of discussion about it (you may remember being on that list yourself!)

There was extensive discussion about using optics as a method of testing apexes. Optics is, in fact, used in the quality control rooms of commercial razor and surgical blade manufactures. I always held out high hope for it to test on a hobby level, but the equipment and skill levels were just too high to make it practical. You have the facilites and the equipment and the skills there at WE to use photos to get very meaningful data on apex conditions and sharpness.

You can give us a good reality check on the jig systems results, and I appreciate that photo you posted very much. It will be very interesting, just fascinating actually, into the future to document with photos the condition of blades that the jig report numbers on.. The way of science and engineering is, of course, careful observation and testing, so we are on the right path here.

[Eamon Mc Gowan]

I’m super excited! :woohoo: My buddy has agreed to make me one. I think it will be a blast to test the different edges! :cheer:

[wickededge]

This machine continues to thrill! I have already started seeing some pretty impressive trends that will greatly inform our techniques and sharpening strategies and for every new thing I learn, the possibility of another 5 things to test opens right up. I’ll do more testing on Monday of the latest thing I’m seeing and then post about it for discussion. Thanks again Dan, this is a terrific project!

For anyone considering building one, I definitely encourage you. It’s inexpensive and easy to build and start testing and you’re guaranteed to have fun and learn a ton.

-Clay

[Eamon Mc Gowan]

My Buddy came over this morning with a preliminary set up. It does not have the triple beam set up yet. He wanted to make sure I really want this thing before he put anymore work and dollars behind it. :S
Right now the “collar” is on a wood handle that I use both hands to push down to cut the tape.
After a couple of “tests”? I told my buddy please have this made by 2:30 this afternoon. :silly:
This is really FUN! :woohoo: Just doing four test knives and I’m sold!
My data is NOT up to speed yet, but I can see where this going and I am very impressed! :cheer:

[wickededge]

Added a new feature to the jig that makes running a series much faster:

Here is the compound table I purchased from Amazon: Proxxon Compound Table It cost $106 and was at my door the next day.

With this table added to the jig, I can knife in the x-axis in increments as small as .5mm, allowing me to take up to 30 measurements for one piece of tape which really speeds things up. I can also easily check the entire length of the blade by advancing the knife in the table on the y-axis. The process is pretty simple:

1. Load new tape
2. Zero the blade in relation to the tool head
3. Zero the weights
4. Add weight until the buzzer sounds
5. Record the force required
6. Zero the weights
7. Advance the blade .5mm on the x-axis and 1 mm on the y-axis
8. Add weight until the buzzer sounds
9. Record the force required
10. etc…

Attachments:

• h0363756.jpg
• he1e1dd2.jpg

-Clay

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