Overheated edge BESS scores

[Bud]

I think that there is a lot to be agreed with here. Common sense and experience has shown me that lots of pressure on high grinding speeds and coarse abrasives can turn an edge blue in fairly short order.  Also makes sense that the idea of dipping a ground edge in a bucket of water may be like closing the barn door after the horses have escaped. It makes sense that slower speeds, less pressure and finer abrasives should also add up to less risk of detempering but I'm not convinced though that detempering edges is the real problem or that slow grinding on a stone solves that problem.  When someone shows me that stone ground edges roll 50 or 70% less than belt ground edges then I'll be a believer. I don't think to date that the tests run have shown anything like those kind of improvements. I may be feeling my oats a bit here and I'm not saying it may not all be true but none of this has been proven, that detempering with belt grinders is the problem or that hand or very slow grinding solves that problem, to my satisfaction yet. Having said all that I will tell you that this discussion is a good one and I appreciate all points of view and opinions.

I love this forum because we do tests. We don't rely on the opinions of self described experts here. I'm not from Missouri but I act like I am, so please, "show me". When you do, I'll thank you for your time and work and if you can't I'll still thank you for your time and work.

[KnifeGrinders]

I think that there is a lot to be agreed with here. Common sense and experience has shown me that lots of pressure on high grinding speeds and coarse abrasives can turn an edge blue in fairly short order.  Also makes sense that the idea of dipping a ground edge in a bucket of water may be like closing the barn door after the horses have escaped. It makes sense that slower speeds, less pressure and finer abrasives should also add up to less risk of detempering but I'm not convinced though that detempering edges is the real problem or that slow grinding on a stone solves that problem. When someone shows me that stone ground edges roll 50 or 70% less  than belt ground edges then I'll be a believer.I don't think to date that the tests run have shown anything like those kind of improvements. I may be feeling my oats a bit here and I'm not saying it may not all be true but none of this has been proven, that detempering with belt grinders is the problem or that hand or very slow grinding solves that problem, to my satisfaction yet. Having said all that I will tell you that this discussion is a good one and I appreciate all points of view and opinions.

I love this forum because we do tests. We don't rely on the opinions of self described experts here. I'm not from Missouri but I act like I am, so please, "show me". When you do, I'll thank you for your time and work and if you can't I'll still thank you for your time and work.

When in the SET test a copper roller is used instead of the steel, the 1425 RPM edges roll by 56% worse than Tormek-deburred.
Using a softer roller in SET testing magnifies the differences in edge holding during the elastic deformation phase, making them readily observable.
It takes 100 copper rolls to deform the edge to the same extent that the steel roller does in the first 5 rolls.



It is clear from both our plant trials and the SET test numbers that, even though overall worsening of edge retention in high RPM edges may not be huge, the peak worsening happens when the edge is the sharpest - edges compromised by high RPM honing lose the initial sharpness quicker, i.e. transit quicker from the initial elastic deformation to the irreversible plastic deformation.
This is exactly what our butcher noticed: "the knife #2 [Tormek-deburred] initial razor sharpness lasted longer"

In simple terms, it matters for very sharp edges.
If your knife application does not require lasting sharpness of < 200 BESS, you can ignore these differences, but now it will be a well-informed consensual ignorance.

[grepper]

The amount of research you do is admirable and commendable Mr. KG! Thanks for publishing your results.

Have you done similar work comparing high vs low speed sharpening as opposed to deburring? As an example, sharpen a blade at high speed and another at low speed and then deburr both on the Tormek.

You post a lot of research so if I missed it apologies in advance.

[Bud]

Thank you for pointing this out Mr KnifeGrinders and thank you for your time and work not just now but for all the information you have reported in the past.

[KnifeGrinders]

No worries, Grepper, Bud... I just want to shift the focus of your attention to the right spot in these findings.
Grepper - the New Zealanders have the data you've asked for. Our SET experiments complement theirs in the area of deburring, and can be considered together.

The New Zealand university researchers, using a different sharpness tester and experimental setup, saw the same pattern in edge holding: the belt sharpened knife dulled about twice as fast as the stone sharpened knife and to a greater degree.
https://waikato.researchgateway.ac.nz

By what we've seen in the New Zealand research and our Australian SET edge rolling experiments, in our trials at the meat plant and with the boning butcher - we can confidently conclude that the difference imparted by sharpening and honing methods matters in the initial performance of very sharp edges in the under 200 BESS range; these differences level out after the first 2 hours of live cutting and/or when the sharpness drops over 250 BESS.
These are dry facts.
The suggested explanations and hypotheses as to why so can be argued, but not the established facts.

Revisiting our earlier supposition that 250 BESS may indicate that the effected area of the apex extends down to the 0.5 micron thick edge, we can estimate the depth of changed steel properties as 0.7 micron for a 40 degrees included edge, and 1.4 micron for a 20 degrees included edge; but this estimate is too hypothetical to take it any seriously.

[EOU]

Really good stuff all - Grepper,KG and Bud. Heat generation is an interesting question as it relates to edge formation and while one grinding methodology may produce edges with greater longevity than another we cannot immediately assume that the difference is due to thermal effects. It may be exactly for that reason but we're not there quite yet. Our experience tells us that really tough problems often contain  multiple components and attempting to lay the source(s) of the problem at any one doorstep is sometimes impossible. In this case, the list of possible components and factors seems lengthy. Complicating all this further is the fact that what seems significant to some may not be significant at all to others.

We will join with Grepper and Bud in this; our thanks is immense for the body of work that KG has generated in the field of edge retention. In our view, KG's opinions are those that must be given great weight because he has done the work and reported his findings generously. KG need not take a second seat to anyone in this industry. Most should be quoting KG, not vice-versa. Does that mean that we won't question or argue from time to time. Of course not, no one has all the answers. We'll just make certain that we are loaded for bear if we do question. Once again - hats off and thanks to KG!

While we're on the subject of discovery we would also like to point to the efforts of Grepper, Ken and Steve G. and we apologise in advance for those we've failed to mention. These guys have sharpened edges, measured them, done something very simple with the edge i.e. cut up a carrot or just let the edge sit out overnight or applied a wood chisel to a block of wood, and then measured it again. These are all remarkably simple experiments that that we all learn an equally remarkable amount from. This is all the real stuff, the findings that advance our knowledge. Thanks to all of you for your reports and experiences, as well.