Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Knife to Belt Pressure vs Bevel Scratching
#1
I was wondering why I was not seeing more of a correlation between an increasing aggressive and toothy edge when I sharpen with a significantly coarser belt abrasive.  My guess was that is was due to the fact that I apply very light knife to belt pressure when I sharpen.  I really don’t push against the belt hard at all, and generally see little or no belt deflection using medium weight belt.
 
Of course a toothy edge is directly related to the depth of bevel scratching caused by the abrasive.  It only stands to reason more pressure would cause the abrasive to more deeply penetrate the steel, and that light pressure would have less penetration.  This obviously results in more metal removal with more pressure than with less.
 
I sharpened the blade using a 120 grit almost new SiC belt applying light pressure like I usually do and produced a dandy burr:
 
   
 
Then I removed the burr:

   
 
 Even though I was not concerned about how sharp the blade was the PT50B was just sitting there so why not?  Approximately in 1/3 increments along the blade from handle to tip the sharpness readings were:
 
210
225
205
 
That seemed a bit dull from what I’m use to seeing so I gave it about 10 strops on my jeans across my thigh just to remove any crud that might still be on the edge.  Then I measured sharpness again:
 
170
170
190

Well, huh.  I wonder what that means?
 
Then I sharpened again, this time applying considerably more pressure on the belt and then performed an apparently sloppy job of burr removal.  I could not see or feel a burr so I figured I was good to go, but as you, dear reader Smile, will soon see, that was a most spurious assumption.  The two images are the same, just different lighting:
 
     
 
Now here’s the freaky part.  It demonstrates not only the importance of complete burr removal but additionally just how deceptive a burr can be.  Furthermore, it illuminates how the combination of both a sharpness tester and a microscope complement and verify the empirical data provided by the other.  Even with all that obvious burr crud piled up on the edge of the blade, the sharpness readings were:
 
160
180
160
 
A bit of a head scratcher, eh?
 
Here’s the direct comparison.  You can observe how increasing pressure produces more frequent and deeper scratches:

   

As always with my tests, take from it what you will.  This was just one test and is neither extensive or conclusive.  Hope you found it interesting.  Smile
Reply
#2
Thank you, Mr. Grepper for sharing your results with us. Smile


My inability to distillate simple lessons from your interesting experiments reminded me the words of the Preacher: "Vanity of vanities, says the Preacher, vanity of vanities! All is vanity. What does man gain by all the toil at which he toils under the sun? …. my heart found pleasure in all my toil, and this was my reward for all my toil." Wink


Reply
#3
What do you mean by, "inability to distillate simple lessons" Mr. Jan?
Reply
#4
Mr. Grepper, my intention was to tell, that sometimes I am not able to evaluate and generalize the results of your tests and draw simple consequences for my own sharpening practice.


Reply
#5
I was guessing that is what you were saying.  Just wanted to be sure.

Can you explain further?

That's the thing about some of the stuff I post.  I try to be clear that these individual tests are neither comprehensive or conclusive, but rather just a single occurrence. What I try to do is to explain what procedure I followed along with whatever empirical data I have available.  Most of the times both the methods and quality/quantity of the data are, in my opinion, not sufficient to really draw any definitive conclusions, so I can more than understand what you are referring to.

I do that stuff in an attempt to better understand what I experience, or to try and discover why something is working or not working when I sharpen.  Sometimes it helps and sometimes not and just leads me to further head scratching.  I figure that since I went to the effort I might as well share it with folks and let them take from it what they will.  For me it's just a learning process.

What would be really cool would be specific feedback, positive or negative, and/or specific questions either about methods, results or the conclusions I dream up from the experience and data.  I mean, everything that I am doing is no doubt a road very well traveled by countless others, probably nothing new, and far better understood already than the point at which I find myself in understanding what I am doing.

So, selfishly, what would be really helpful to me in furthering my attempt to understand sharpening would be if when you think something is ambiguous, or misleading, or incomplete and requiring a richer data set or whatever, to share some specific questions, or possible direction for further exploration.  That sort of thing.  Or even just blurt out What a Bunch of Crap! Tired  At least then I could inquire, how so?  Moreover, it might help me to do a more refined or comprehensive experiment that may better resolve a question.  That's what I'm trying to do with this stuff and why I bother to post it.

So, thank you Mr. Jan for you comment.  It's truly appreciated!  Please continue. Cool
Reply
#6
Grepper and Jan,

I have some understanding of both sides of this. As you both know, I have investigated and done rudimentary testing of several issues for the Tormek forum. I believe that my testing and reviews offered some value for anyone considering purchasing any of the tools or jigs involved. I have never pretended that my tests or reviews were exhaustive. 

When I tested the Norton 3X wheels, I did purchase both grits, 46 and 80. I have invested around a hundred dollars total in the two wheels. To compare the two Norton wheels, and to vompare them with the conventional Tormek wheels, I devised a standard test. I placed 5/16" metal lathe bits in the Tormek square edge jig and compared how much steel was ground away after five minutes. I consider this a good indicator, but hardly definitive. The scientist part of me would prefer a more thorough test. The accountant and time manager in me did not need to be so thorough.

Any of these tests would benefit from posts shRing experiences from other members.

Family calls....must dash.

Ken
Reply
#7
Yeah, I don’t really consider the stuff I post as tests, more just some pictures of what I did and a hopefully entertaining little story of what happened.  It would be cool if something can be gleaned from it, but other than that it simply is what it is. 
 
Personally I like the pretty pictures and sometimes I actually find them interesting and informative, other times it just leaves me wondering and wishing I had an electron microscope!  Sadly I don’t think that will come to pass.   Rolleyes  
 
Really, I just enjoy sharpening and learning and try to have some fun with it. Smile
Reply
#8
Thanks, for your explanations, Mr.Grepper. Thanks, Ken, also.

I am afraid that my comment was misunderstood. As I have stressed, the words of the Preacher were meant to describe my situation, "My inability to distillate simple lessons from your interesting experiments …"

As you know I am non-native English speaker and so to fully understand some posts here may be a challenge and some toil for me, despite the fact they are nicely written and well photo documented. When it happens that I am not able to learn a lesson from a post, I am unhappy, and feel that my effort was in vain. That was the reason to quote King Solomon. Wink


Reply
#9
Jan,

You do not have an English language problem. Your posts are carefully crafted and your typing is more accurate than many of us for whom English is our first and often only language.

As a telephone troubleshooter, I became accostumed to a precise language of electrical and noise testing. I would become uncomfortable with incomplete or inconclusive testing. With your highly developed mathematics and scientific skills, a test procedure which is unfinished must sound like Bach being played out of tune on a not so well tempered Klavier.

I believe Grepper's testing will eventually produce fruit. At this point, the testing is a work in progress and the garden is not quite harmonious. As the Preacher wrote in the Book of Ecclesiatics, "For everything there is a season". The fruit is not quite in season.

I am happy that we have this forum as a means to increase and share our knowledge.

Ken
Reply
#10
Thank you, Ken. The misunderstanding was already explained via PM. Wink


Reply


Forum Jump:


Users browsing this thread: 1 Guest(s)