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TOPIC: Stroke Direction

Stroke Direction 11 months 1 week ago #13545

  • wickededge
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This is slightly off-topic but concerns the same blade I've been working with. I went ahead and spent more time erasing the majority of scratches with the .25um diamond and .125um CBN on kangaroo strops. Here is a nice picture of the blade at 2000x:

hc592577.jpg

.125um CBN on Kangaroo Strops - 2000x Magnification

I ended up increasing the angle a little, coming back to one degree less than what I'd been using for the stones. The slight convex shaping that occurred is easy to see and the resultant loss of cutting performance was easily detected with the hanging hair test. The blade went from easily scoring HHT5 to scoring HHT4 with the occasional HHT5. Clearly that slight bit of rounding of the edge is something to keep in mind when finishing a blade, especially when pursuing a mirror polish. I think we'll get a separate post going about what one's goals might be in stropping.
--Clay Allison
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Stroke Direction 11 months 1 week ago #13546

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LeoBarr wrote:
One thing I have missed is what type of steel are you using for these tests I have read that the latest wonder steel is hap40 a powdered steel from Hitachi with a possible rockwell hardness of 68 this steel I have read has incredible edge retention capabilities so much so someone nicknamed it voodoo steel since it holds an edge so well!
I think the work is most interesting sharpening techniques must have different results on different steels would they not .
Early days I am sure but these Hitachi super steels must respond differently when sharpened to say the steel of Henkels or Worstoff .
I wonder if there is less of a need for extensive stropping on these super steels would not the whole appearance of these super hard steels have a much finer appearance under high magnification therefore producing a far finer edge.(say at a near molecular level would the steel be closer knit I would expect say a poor quality steel to have more impurities therefore a less dense structure)
This is pure speculation on my part with a very basic knowledge of metallurgy & chemistry.
Perhaps your test will bear this out.

Leo, the blades I'm using are 'high carbon' utility blades. I like them because I can buy them in bulk and they're quite consistent, making it easy to compare edge geometries and finishes side by side.
--Clay Allison
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Stroke Direction 11 months 1 week ago #13550

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I ended up increasing the angle a little, coming back to one degree less than what I'd been using for the stones. The slight convex shaping that occurred is easy to see and the resultant loss of cutting performance was easily detected with the hanging hair test. The blade went from easily scoring HHT5 to scoring HHT4 with the occasional HHT5.



Interesting Clay, but not unexpected I guess.
Did you do any tests with the sharpness tester to see if the changes in the HHT correlate to anything measureable with that device?
Phil

MAX 2001-2013
Hoping there is that bridge!
I miss you Buddy!
Last Edit: 11 months 1 week ago by PhilipPasteur. Reason: wrong quotes.. I give up..
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Stroke Direction 11 months 1 week ago #13551

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PhilipPasteur wrote:
I ended up increasing the angle a little, coming back to one degree less than what I'd been using for the stones. The slight convex shaping that occurred is easy to see and the resultant loss of cutting performance was easily detected with the hanging hair test. The blade went from easily scoring HHT5 to scoring HHT4 with the occasional HHT5.



Interesting Clay, but not unexpected I guess.
Did you do any tests with the sharpness tester to see if the changes in the HHT correlate to anything measureable with that device?

I didn't get to the sharpness testing machine today but definitely will tomorrow.
--Clay Allison
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Stroke Direction 11 months 1 week ago #13557

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wickededge wrote:
This is slightly off-topic but concerns the same blade I've been working with. I went ahead and spent more time erasing the majority of scratches with the .25um diamond and .125um CBN on kangaroo strops. Here is a nice picture of the blade at 2000x:

hc592577.jpg

.125um CBN on Kangaroo Strops - 2000x Magnification

I ended up increasing the angle a little, coming back to one degree less than what I'd been using for the stones. The slight convex shaping that occurred is easy to see and the resultant loss of cutting performance was easily detected with the hanging hair test. The blade went from easily scoring HHT5 to scoring HHT4 with the occasional HHT5. Clearly that slight bit of rounding of the edge is something to keep in mind when finishing a blade, especially when pursuing a mirror polish. I think we'll get a separate post going about what one's goals might be in stropping.

Ok, I just read this again and the other post is no fair... you have to take new photos lol. Man, I love seeing what happens on a microscopic level! It really makes sharpening come alive and allows us to achieve optimal sharpness based upon our research here. This is one thing that totally makes the WEPS shine... not only the support and on-going research, but what other system can you create a perfect bevel and then lower it 2*/side precisely when you move to strops? Of course you can w/ the Edge Pro, but its not conducive to that system (since you would have to "pull" the arm toward you with each pass after you custom mount the strop that is =)

going to have to re-think my straight razor strategy... I haven't been lowering the angle because I wanted the edge to be sure to be hit to erase all of the prior scratches, but clearly that is not the case and is not achieving optimal sharpness for my purposes.
Last Edit: 11 months 1 week ago by razoredgeknives.
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Stroke Direction 11 months 1 week ago #13559

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Do you think that say if you allow a small amount of convexing to occur that the blade has a chance of retaining albeit slightly inferior sharpness for longer than a total "V" profile ?
I suppose a great part of that answer would depend upon the use of the blade and once again the quality of the steel so I guess there is always going to be two answers one to pass the ultimate sharpness test and the second to retain a serious level of sharpness.
These sharpness tests will certainly help the WE owners no end but there will be so much more testing to do to answer all the questions of how to sharpen for a purpose .
Food preparation requires various forms of sharpness from a toothy edge , a strong edge through to a razor type of edge and identifying what edge is best suited is not always that clear when we are sharpening for someone else. It seems the more we dig the more complicated the answer becomes.
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Stroke Direction 11 months 1 week ago #13560

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I wondered how long it would be before convex fans started piping up in defence of a rounded edge :)
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Stroke Direction 11 months 1 week ago #13564

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PhilipPasteur wrote:
Interesting Clay, but not unexpected I guess.
Did you do any tests with the sharpness tester to see if the changes in the HHT correlate to anything measureable with that device?

I just ran the numbers from the sharpness machine and found a pretty nice correlation:

Blade stropped 2° below the sharpening angle required an average of 186g to rupture the tape and consistently scored HHT5 .

Blade stropped at the sharpening angle required an average of 204g to rupture the tape and consistently scored HHT4 with an occasional HHT5.

I think there is a way to test the durability of the edge with the two different techniques using the sharpness tester. I'll need to set up a second blade so I can do side by side comparisons, one stropped at angle and one stropped below. With a high number of sharpness tests in the same place on each blade, I should be able to see the loss in apex point sharpness over time. I can also degrade the edges at the same rate by keeping the same load on each and moving the blades along their y-axis. Repeated motion under load should degrade the edge measurably and I can then perform the sharpness test again along with the hanging hair test to see which blade, if any, held up better.
--Clay Allison
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Stroke Direction 11 months 1 week ago #13571

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Clay, very interesting results! It would be interesting if you could do a sharpness test as well before you do any stropping. In that way we can see what the effect of a little bit of stropping is.

I assume you are using a leather strop? I'm also interested in what a harder material, like balsa or glass-mounted nano-cloth would do.
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Stroke Direction 11 months 1 week ago #13573

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wickededge wrote:
Some Faith Restored! :)

I'll post a whole write up soon, but for now I'll leave the following: I took a blade up through 10k Chosera and then on to the .25um kangaroo strops. At 10k it wasn't really popping hairs in the hanging hair test, but after the roo strops, it was consistently returning values of HH4 and HH5 (reference here). From there, I took it to the sharpness tester and got great results: 34% less force than with the 100# plates.

How did you solve this (or did I overlook the answer)?


DanMaloon wrote:
I was about to start to sharpen knives on cinder blocks haha

:lol: :lol: :lol:
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