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Sharpening story - pesky knife to sharpen
#1
I was given a dozen knives to sharpen, 6 steak knives, 4 8” chef’s knives and a couple of shorter santoku.  Nothing special, just average good quality knives.  Except for one they were Henckels type variety with modern sealed mostly impervious to anything plastic like handles.  You know the type.
 
One however had a wood handle.  The handle was totally dried out and starting to show small cracks.  The type of damage that occurs during the heat cycle in a dishwasher.  I didn’t think to take a picture of it because it was just another knife.  Nothing remarkable, just a wood handle knife.  It looked exactly like this one I found on ebay. 

   
 
I checked it out before I sharpened it and there were a number of small chips in the edge.  The chips weren’t very big.  I didn’t think much of it and went about sharpening with my usual method using a 150 grit Cubitron and deburred with a Scotch-Brite belt.  When I was done I checked it out and the chips were still there.  Crap!
 
So I reground the edge but the chips seemed to propagate.  I couldn’t seem to grind away the little chips out of the edge.  Very frustrating.  So I reasoned that maybe the 150 grit was too coarse and switched to a used 180 grit Deer ceramic belt.  For whatever reason that worked and removed the chips.  Then I deburred as usual with the S-B belt.  The blade was nice and sharp, well deburred and no doubt not bad at all.
 
But… the 180 grit belt that I used was pretty old and no longer really 180 grit.  I imagined that that I was not giving the guy as toothy an edge as I would like.  So, I started over and reground the edge with the 150 Cubitron.  This time, for whatever reason it worked.  No chipping. 
 
I’m not sure what was happening with that blade, but I needed to get rid of the chips with a finer grit abrasive before I could grind with a 150 grit for a nice toothy edge. The steel didn’t seem particularly hard but it was prone to chipping.  Live and learn I guess.  I spent well over an hour on that knife.  When I was done the sharpness ranged from 130-170 along the edge.  Not as consistent as I would like, but plenty sharp enough and nice and toothy. 
 
But I wasn’t done yet.  It was a nice knife and it bothered me that the handle was so dry and starting to crack.  I returned all the other knives but kept that one for two days.  I gave he handle a good thick coat of a combination of mineral oil, carnauba and bee’s wax.  Then put the knife over the heat register and let it all soak in for hours, wiped it clean and repeated the process.  I did that 3 or 4 times over the two days.  When done, the handle looked really nice and was in much better condition.
 
Unless it’s for a friend I actually charge for sharpening, but have no illusions about making any money doing.  I do it for fun because I enjoy it.  I charge $2.00 for less than 5” blades and jack the price up to a whopping $2.50 for > 5” blades, not counting really long blades like machetes.  Over many years I’ve made just enough to pay for the Kally.  What more could I ask?
 
Anyway, I think the guy got a good deal for $2.50.  Hope you enjoyed the story.
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#2
Add one LIKE from me, Grepper. Interesting and informative post.

Ken
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#3
Mr. Grepper, in my understanding your interesting observation could be explained by the fact that Cubitron II ceramic grains are precisely shaped to triangular forms. Even more the grain structure is micro replicated. Cubitron II cuts the steel surface and in some tougher steels it can generate long chips. Steel chipping is difficult to fix, such a steel is not suitable for knife blades. The harder the steel the less tough it usually is.

Jan


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#4
Great to see you back Mr. Jan.  I’m a Cubitron fan and would even wear a Cubitron branded hat if someone gave me one.  The belts cut really well, last a long time and maintain a consistent grit level longer than any other belts I’ve tried.  I also like the even way they feel when grinding.  I have both the regular Cubitron and Cubitron II belts.  The 150 grit belts I use are regular Cubitron, not the newer Cubitron II.  The last I checked the newer Cubitron II belts were only available in coarser grits.

I’ve seen the 3M add copy showing the pointy Cubitron II abrasive crystals all standing at attention on the belt surface ready to go to battle. 

   

Here is a microscope image I took of a new 120 grit Cubitron II belt. 

   

To me it looks more like the irritated skin of a red faced teenager suffering with zits, blackheads and ingrown hairs than an army of pointy little abrasive particles magically adhered and standing at attention on the belt surface.  Maybe I need a more powerful microscope to see it.  That said, those 120 grit Cubitron II belts are very sharp, cut like crazy and are great belts when 120 grit is needed.  I’ve tried it and they are too gnarly for knife sharpening, but are most excellent belts nonetheless.

It was an interesting blade to sharpen.  It apparently had chipped during normal use.  It didn’t seem like particularly hard or for that matter soft steel when I ground it.  Just sort of normal.  For whatever reason 150 grit seemed to propagate the chipping but after getting the chips out with a finer abrasive regrinding with 150 grit worked okay.  Maybe the very edge had become brittle and grinding with the finer abrasive just happened to get down to stronger steel.  Maybe if I had continued with the 150 grit the same thing would have happened.

Good to see you back again too Ken!
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#5
Love the "adventures of sharpening" stories here! I am reminded of how much I need to study, learn, and try techniques.

Thanks!
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#6
Mr. Grepper, thanks for your explanations. Your microscope image of the Cubitron II belt is not similar to the 3M image. Hopefully at larger magnification it would be better.

I use 60 and 80 grit Cubitron II belts (984 with weight backing) for knife blank shaping. It cuts really fast, both carbon and stainless steel. The 150 grit Cubitron II belts are not commonly offered in this country. My belt size is 2 x 60" (50 x 1500 mm).

Jan


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#7
In my experience, with chips of a certain depth, you almost can't get rid of them by sharpening in a normal way.  If you zoom in to the edge in your mind and imagine the grains of the belt running into the edge...  Where those grains hit the chips, they want to drive those chips deeper.  Those valleys just continue to be valleys because the grains almost "catch" in the smallest part and drive that smallest pointed part of the chip, deeper into the edge.

The most reliable way I've found to fix this is to grind the edge at 90 degrees, making the edge flat.  This will produce an extremely dull flat edge, but you will know the chips are gone for SURE before you start putting an angled bevel back on the blade.  A nice side effect is, with many edges that are damaged and chipped, they might need a little reshaping too.  So you can get the shape exactly how you want it before you start the sharpening process.

After grinding in new bevels, the blade should look great.

Brian.
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