Knife to Belt Pressure vs Bevel Scratching

[grepper]

I'm not quite sure what this is even about. Just to be clear, there was never any misunderstanding at all. Not even in the slightest. Just normal conversation as far as I could tell.

[Mark Reich]

It is always easy to misconstrue anyones' posts on any forum. Nature of the beast. I know I can't always convey the right message in any single post.

Mr. Grepper, I understand your quest for maximum tooth, and I've enjoyed pursuing your grail for my own betterment.

IMHO, the shape of the abrasive particle is more important than it's size. Sharp particles leave sharp teeth. Worn or smoother particles can't leave sharp scratch patterns. Even though the scratches may be bigger with larger grit, that doesn't necessarily give your edge more tooth.

The most obvious manifestation is the difference between a brand new belt and one that's been slightly used.

The next best example is different types of abrasive compounds on hones. CBN is very nearly as hard as diamonds, but the particles are smoother. CBN removes a burr much better than diamond, but diamond leaves much sharper teeth.

I often deburr with boron carbide or CBN, then give the edge tooth with diamond compound.

I forgot to address the issue of "pressure" against the belt- IMHO, more pressure is almost always detrimental to the edge, no matter if it's against a belt or stone or hone. Great sharpening requires a delicate touch, not a heavy hand.

[Ken S]

Interesting post, Mark, on many levels.

Yes, unclear communication happens occasionally. Sometimes we realize what the person meant to say. Sometimes we don't. One of the many things I like about this kind of group is not being embarrassed when I do not understand something. Going back to explain something clarifies the subject for both the listener and the speaker. 

Your comments about the sharpness of the abrasive particle being more important than its size ring true for me. I have long known that a Tormek grinding wheel cuts most agressively right after being trued with the truing tool. The abrasive particles are not larger. They do not grow. The diamond truing tool just removes worn grains and exposes fresh (sharp) grains. Supposedly the stone grader strips away some of the binding, making the stone more agressive. It does that, however, not as much as the truing tool by exposing new sharp particles. 

I do not mean to imply that my thoughts pertain only to the Tormek. They do not. Since 2009, my sharpening has been mostly with the Tormek. That has become my frequent point of reference.

IMHO, one of the difficulties with pressure with grinding is that the subject is dynamic, not static. Traditional Tormek technique encouraged heavy grinding pressure. That works well with the SG-250, the traditional SuperGrind 250mm grinding wheel. That wheel is designed primarily for carbon steel. It cross functions with high speed steel, however, it is really designed for carbon steel. Tormek's "blackstone", the SB-250, is a harder stone, designed for harder steel. If you use it as the same higher pressure, it will quickly glaze and stop cutting. It works best with light pressure.

Pressure is one of those grinding issues which makes me realize that the more I learn, the wider my unlearned gap becomes. I am not complaining; that is one of the many things which makes sharpening so fascinating.

Good post, Mark.

Ken

[grepper]

Mr. Mark uttered, “IMHO, the shape of the abrasive particle is more important than it's size. Sharp particles leave sharp teeth. Worn or smoother particles can't leave sharp scratch patterns. Even though the scratches may be bigger with larger grit, that doesn't necessarily give your edge more tooth.”

I mostly agree.  Sharper particles cut steel better and produces better tooth.  Not doubt about that.  However, IMHO, sharp larger particles produce larger, more separated scratches and hence a more gnarly edge.  Taken to extremes for example, a new 1000 grit belt won’t produce as toothy an edge as a new 80 grit belt.
 
“The most obvious manifestation is the difference between a brand new belt and one that's been slightly used.”
 
I totally agree and I hate that!  Nothing like the first couple of passes on a new belt.  I just wish they stayed that way longer.  It sure doesn’t take long before the reduction in cutting in obvious.  I’d love to have a 120-150 grit diamond belt, but not only are they hard to find, they are extremely expensive.  As I remember, close to $200.  Way more than I’d pay for belt!
 
“I forgot to address the issue of "pressure" against the belt- IMHO, more pressure is almost always detrimental to the edge, no matter if it's against a belt or stone or hone. Great sharpening requires a delicate touch, not a heavy hand.”
 
Yup.  Unless I’m trying to hog off steel, I use very light pressure.  So light in fact that there is almost no visible deflection of the belt even sharpening a couple of inches above the platen on the Kally.  No heat either.

[Mark Reich]

Thank you very kindly, Gentlemen. I'm encouraged by your open minded consideration.

Mr. Grepper, have you found a balancing point between maximum tooth and minimum refinement for day to day use and maintenance sharpening?

[grepper]

I really appreciate this conversation about toothy edges!
 
I thought I had found happiness with a 180 grit Deer ceramic belt.  It produced a pretty toothy edge but after only a few knives it seemed to really smooth out.
 
Yesterday I sharpened a blade with a new 80 grit SC belt.  It cut the steel great and produced a wonderful, very toothy edge, but was very difficult to get deburred.  I tested the blade by pulling it through plastic/nylon bailer twine.   I like that stuff to test with because a non-toothy edge, unless it is super sharp, just rides on the plastic.  The 80 grit edge dug right in and cut the twine in about ¼ of the blade length as I pulled it through the loop of twine, while a 180 grit finished edge took most of the blade length.
 
My experience with SC belts is that they cut exceptionally when new, but don’t last long at all and soon get smooth.  I was hoping the ceramic Deer belt would last longer and it did, but not that much longer.  I notice that Deer makes a ceramic belt for high pressure grinding and they say it takes a lot of pressure to fracture the crystals.
 
With ceramic belts, is fracturing the crystals good?  Does that keep it sharp, or do I want a very hard to fracture tougher ceramic?  Will Zirc belts stay sharper longer?  I don’t know the difference between ceramic and Zirc.  Much to learn still.
 
Mr. Mark queried, “Mr. Grepper, have you found a balancing point between maximum tooth and minimum refinement for day to day use and maintenance sharpening?”
 
To answer your question Mr. Mark, basically no.  Not yet.  But I was really happy with the 80 grit edge!  Now I’m thinking maybe about 120-150 grit may be what I’m looking for.  I keep going for a coarser and coarser grit.  80 seems a bit rough and 180 grit not really coarse enough.  I suspect one reason I like such a coarse abrasive is because I use such light belt pressure when I sharpen.

Your question combining max tooth and minimum refinement for day to day maintenance is a difficult one.  It's that day to day maintenance part that makes the question difficult!  I'm still just trying to get maximum tooth!   I'll have to figure out the second part later.
 
What I do know however is that for general use, anything that requires slicing, an edge with good tooth seems to really outperform a smooth edge.  If I could only find belts that stayed sharp longer!

[Mark Reich]

Good catch, Mr. Grepper! Indeed, the question is one of practicality.

[Ken S]

Speaking of longlasting belts, I remember a Sorby demonstrator discussing their selection of grinding belts. When he came to the diamond belt and the cost, he pretended to cough and said in a concealed voice, "two hundred dollars".

Hopefully there is a middle ground which will last half of forever and cost less than an arm and a leg.

Ken

[Rupert Lucius]

This past week I, realized that I needed to replace two Tormek 10" wheels.

Called Grizzley parts and asked the price for their 10" wheel parts number T20683 for Grizzly "want to be a Tormek" T10010) 39.95 plus shipping 9.99 total delivered 49.94$.

Used it today the 12 mm shaft hole perfect for the Tormek, removed the paper label from one side of the wheel and  was a able to catch  two threads on the Tormek shaft.  Worked AOK!

Tested it on a dull 9 inch 440C chef knife at 15* - the sharpened edge was toothy enough for me (approximate to belt grit 120 minus).

Created a burr that I have not tried to removed.  Did straighten said burr on a cotton buff. Ken's modified Viel running a leather belt in low gear would be perfect for said removal.

Approaching fresh harvested tomatoes laying on our kitchen table - they ALL jumped off the table.

Another bargain - my opinion.

Will order the second wheel tomorrow.

Rupert

[Mark Reich]

I took my eye off the ball, Mr. Grepper. Let's get the gnarliest edge accomplished, then you can determine other parameters.

For a 1x42, this is the gnarliest belt I know of. It's not the coarsest, but I haven't heard of anyone trying to get a clean 80 grit edge until now. 

Longest lasting belts I've found. One belt should vaporize many blades before it starts to slow down.