EDGE RETENTION/ROLLING PART II

[EOU]

Well that's very interesting stuff KG and much in-line with what we've seen and expected.  Seems to us that any resultant  decline in sharpness after tens or hundreds of cycles might be due to a gradual and miniscule chipping away at the apex by the steel roller. Perhaps even turning the apex into just dust. The kind of tiny and gradual degradation that can't be seen even by one of our optical microscopes unless a large chip get's broken out. We've developed enough breathing space here to get Mark's SET unit out to him this week so perhaps he can test his Kyocera knife and see how it performs next to the cheap ceramic knives that both of us have tested. 

To date we have edges that roll but don't chip and edges that don't roll but chip. Perhaps edges that don't roll or chip are next. In that vein, we had a conversation with Peter's Heat Treating today. Seems as if they have been delayed by the Blade Show but are back on track now. Our test pieces should be on the way back to us tomorrow.

[KnifeGrinders]

You're going to have to let us in on your secret KG. If we read correctly your ceramic knives were sharpened to BESS 100 when your ceramic knife SET test began. We had trouble trouble breaking 300. We purchased some 1 X 30" diamond belts and a top-of-the-line Harbor Freight ($55.00) belt sander to run them on and went to work. It seems to us that ceramic blades like small diamonds. We couldn't get below 400 with the 30 micron and but then did get below 300 (288) when we switched to the 20 micron and very light pressure. Any suggestions for how we "all thumbs" Arizonans might up our game?

What we know of steel sharpening cannot be extrapolated to ceramic.
Unlike steel blades, where you get a well cutting edge off the grit  #400 (30 micron), and a shaving edge off #1000 (20 micron), the ceramic edge will be blunt after #400, and hardly cutting after #1000 - it has to be sharpened further on the finer grit of 5-6 micron (#3-4000) to get it sharp.

Have a look at our BESS scores we get in the process of sharpening ceramic, they are similar to you numbers, and generally speaking correlate with the abrasive grit more than the steel.

CBN#400 500-700 BESS >>  CBN#600 500 BESS >> CBN#1000 280-400 BESS >>  5 micron diamond 105-120 BESS >> 0.5 micron diamond 55-90 BESS

[KnifeGrinders]

Ceramic knives are long lasting slicers, but unfortunately have no place in the boning room.
Our boner tried our ceramic knife sharpened at 15 dps for dividing cuts not touching the bones. The knife performed well, however by the end of the day the edge had multiple macro chips and even dents just from cutting through ligaments and tendons. The ceramic knife would need daily re-sharpening if used by butchers, making them not feasible for them.

[subwoofer]

What we know of steel sharpening cannot be extrapolated to ceramic.
Unlike steel blades, where you get a well cutting edge off the grit  #400 (30 micron), and a shaving edge off #1000 (20 micron), the ceramic edge will be blunt after #400, and hardly cutting after #1000 - it has to be sharpened further on the finer grit of 5-6 micron (#3-4000) to get it sharp.

Have a look at our BESS scores we get in the process of sharpening ceramic, they are similar to you numbers, and generally speaking correlate with the abrasive grit more than the steel.

CBN#400 500-700 BESS >>  CBN#600 500 BESS >> CBN#1000 280-400 BESS >>  5 micron diamond 105-120 BESS >> 0.5 micron diamond 55-90 BESS

Does this suggest that instead of actually cutting the ceramic, a diamond particle is removing material by chipping it away. So due to the roughness of this chipping, compared to steel, a much finer grit size is required to achieve the same fineness of edge?

[KnifeGrinders]

I think the same, sharpenging through chipping it is the most plausible mechanism.
The above results are for edge-leading grinding where chipping is a given; if the "sharpenging through chipping" is true, then edge-trailing would work worse.
To check that, I tried twice to grind edge-trailing on Tormek, using our Frontal Vertical Base and got sharpness worse by 100-200 BESS, no matter how long I would spend on the wheel.
It is "sharpenging through chipping".

[Mark Reich]

Hmm. Well, thanks for figuring out how to sharpen ceramic, KG. I'm impressed you got them <100 BESS, but it sucks to have to refine them to 30,000 grit.

Are you sharpening edge leading on your belts, Mike? Where did you find diamond belts?

Sounds like you need exactly the right equipment, and sharpening them on anything besides a Tormek is not going to be easy.

How long does it take to sharpen a ceramic blade, gentlemen? What is your grit progression, and what angle are you using?

[Mike Brubacher]

Thanks KG. Makes sense to us and perfectly in-line with our suspicions. While diamond seems certainly the abrasive of choice with ceramic, I think that ceramic and diamonds are a bad combination in this sense; Diamonds want to cut as opposed to grind in the traditional context of the word. Ceramic is so hard though that it resists cutting. Diamonds are going to win that battle but may do so in the form of "tearing" as opposed to cutting. The result is large chunks of material being removed during the sharpening process. It makes perfect sense that smaller diamond particles would result in smaller chunks of ceramic material being ripped asunder. Large chunk removal is not conducive to sharp edges. In addition, I think that two other very real impediments to ceramic edges still remain; (1) there is a very real possibility that ceramic edges sharpened to levels at or below 200-300 BESS are simply not practical edges for normal use due to the increased likelihood of chipping which brings me to the second impediment; (2) I always suspected that ceramic knife manufacturers produce  out-of-the-package blades that are relatively dull i.e. 325-450 BESS for a reason. That reason would be that duller ceramic edges have less of a propensity to chip. My hope was that a ceramic edge at 275-300 could be produced that embodied lots of "tooth" thereby compensating for the reduced sharpness level in many slicing applications. This hope seems out the window now if twenty micron abrasives must be used to achieve 300 BESS sharpness scores. 1000 grit  doesn't leave much "tooth". 150-180 grit does (at least in a steel knife). 

Having said all that I still think that ceramic knives have their place in the world's home kitchens and, on average, may even be the best choice. Here's why I say this; If you are able to find a home chef who actually makes an attempt to sharpen, the attempt will likely be made with a counter-top electric sharpener. Perfectly executed and on a very good day that electric sharpener may be able to turn out a 300 edge. If I was reduced to cutting with 300 edges in the kitchen I'd just as soon be using a ceramic blade as opposed to a steel one because the steel edge will measure 370 within a half-hour's use and the ceramic will still be at or near 300. The steel edge could  be back to 300 before the next use but almost no one is going to take 10 seconds time to straighten the edge before each use. Instead they'll start cutting with the, now, 370 steel edge and by the end of the current food preparation session it will be 400 (roll rate slows as the roll increases) and so on and so on. For those who do not attempt and become fairly proficient at sharpening? Two years later their nice Wusthof steel knife edge will measure 1200 - 1400 and that's just the way it goes. If you'd purchased a $15.00 ceramic you could have likely enjoyed a years worth of nearly effortless cutting and slicing and then tossed it (accumulated chips and all) and gotten a new one.

So there you have it - ceramic versus steel in the home kitchen as seen by Mike Brubacher.

Note: Much of the above opinion is based on research that has yet to be conducted and evidence that has not been presented so I hereby reserve the future right to do a complete and total flip-flop on the matter once I'm proven wrong.

[Rupert Lucius]

Thanks KG. Makes sense to us and perfectly in-line with our suspicions. While diamond seems certainly the abrasive of choice with ceramic, I think that ceramic and diamonds are a bad combination in this sense; Diamonds want to cut as opposed to grind in the traditional context of the word. Ceramic is so hard though that it resists cutting. Diamonds are going to win that battle but may do so in the form of "tearing" as opposed to cutting. The result is large chunks of material being removed during the sharpening process. It makes perfect sense that smaller diamond particles would result in smaller chunks of ceramic material being ripped asunder. Large chunk removal is not conducive to sharp edges. In addition, I think that two other very real impediments to ceramic edges still remain; (1) there is a very real possibility that ceramic edges sharpened to levels at or below 200-300 BESS are simply not practical edges for normal use due to the increased likelihood of chipping which brings me to the second impediment; (2) I always suspected that ceramic knife manufacturers produce  out-of-the-package blades that are relatively dull i.e. 325-450 BESS for a reason. That reason would be that duller ceramic edges have less of a propensity to chip. My hope was that a ceramic edge at 275-300 could be produced that embodied lots of "tooth" thereby compensating for the reduced sharpness level in many slicing applications. This hope seems out the window now if twenty micron abrasives must be used to achieve 300 BESS sharpness scores. 1000 grit  doesn't leave much "tooth". 150-180 grit does (at least in a steel knife). 

Having said all that I still think that ceramic knives have their place in the world's home kitchens and, on average, may even be the best choice. Here's why I say this; If you are able to find a home chef who actually makes an attempt to sharpen, the attempt will likely be made with a counter-top electric sharpener. Perfectly executed and on a very good day that electric sharpener may be able to turn out a 300 edge. If I was reduced to cutting with 300 edges in the kitchen I'd just as soon be using a ceramic blade as opposed to a steel one because the steel edge will measure 370 within a half-hour's use and the ceramic will still be at or near 300. The steel edge could  be back to 300 before the next use but almost no one is going to take 10 seconds time to straighten the edge before each use. Instead they'll start cutting with the, now, 370 steel edge and by the end of the current food preparation session it will be 400 (roll rate slows as the roll increases) and so on and so on. For those who do not attempt and become fairly proficient at sharpening? Two years later their nice Wusthof steel knife edge will measure 1200 - 1400 and that's just the way it goes. If you'd purchased a $15.00 ceramic you could have likely enjoyed a years worth of nearly effortless cutting and slicing and then tossed it (accumulated chips and all) and gotten a new one.

So there you have it - ceramic versus steel in the home kitchen as seen by Mike Brubacher.

Note: Much of the above opinion is based on research that has yet to be conducted and evidence that has not been presented so I hereby reserve the future right to do a complete and total flip-flop on the matter once I'm proven wrong.

Again our Master is "spot on".

Rupert

[Bud]

Do you have the test samples yet? This is like waiting for the "Who killed J.R.?" episode.

[EOU]

"This is like waiting for the "Who killed J.R.?" episode."

Man, we're all showing our age here Bud. Dallas was past bedtime for some of our members. We had to look that one up. Kristen, the scheming sister-in-law, shot JR in early 1980 but we had to wait an additional eight months to find out if JR would survive and who his assailant was. We don't think that we'll have to wait that long in this case. Thanks for your interest Bud. If everything went as planned last week, we should receive them today or tomorrow. We'll put up a picture here as soon as we get them out of the box. In the meantime we'll confirm with Peter's that they have been shipped. If something has changed, we'll let everyone know.