Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Don't Shoot the Messenger
#1
Hello Exchange Members!

About a week ago an industrial customer of ours called with, we won't say a complaint, but what we prefer to think of as a "question". The question was this; they'd been testing recently received and brand new cutting tools from their supplier and getting erratic readings on their multiple point edge sharpness tests. Anywhere from 260 to 480 on a single edge that was only 1.5" wide. First a little background though before we go further with this story:

We deal, typically, with process engineers at these companies. Process engineers have to wear many hats. They have to be able to diagnose problems in their 4-20ma current loops and select the right load sensor for a batch blending operation. If their manufacturing facility is also engaged in processes that cut, slice, shear or chop things then they have to contend with issues germane to edges as well. You can't be an expert at everything. That's why we get a lot of calls from those engineers who are experiencing problems relative to product quality, through-put, and/or cost of operation. In this case, the problem turned out to be one that applies to anyone who ever ground an edge so we thought that we would share it here. 

So the company engineer agreed to send us a few samples of the new blades they had received from their supplier. The first thing we did was have a nice close look at the edges. Here is an optical microscope picture of the first edge we looked at:

   



It's easy to see why this edge would produce inconsistent readings. To the left, the edge is a mass of residual burr. To the right the burr is not quite so prevalent. Their edge test results were telling them exactly what the picture shows. This is what edge testing is really all about. Not just how sharp your edge is at the end of a sharpening session but using it as a diagnostic and learning tool. So OK we've all seen pictures of burr before but these edges weren't quite finished telling their story yet. Here's another picture of another blade that came from the same group of samples provided.

   

Believe it or not, this picture was taken after having been worked over with a leather belt mounted on a Kally.  We tested it after deburring with the Kally and it still wasn't sharp so back to the microscope. The edge has been buffed up nicely but essentially, now, the burr side of the edge is a scraper. It looked, sounded and felt like a scraper as well when this side was drug across the surface of a leather hone. The top 75% of the burr has been removed leaving this stubby and substantial base. The shiny, almost weld-like look of the burr is rolled toward you in the picture. That's why it's shiny, it's reflective angle is different than the bevel portion of the edge. Our experience says that burrs like this occur when too much grinding force (or speed) has been used. Our experience also tells us that the only way to remove this burr is to grind it off. Hopefully with less applied force and speed the next time. 

We're very open to other theories and interpretations regarding these pictures. We say the top 75% of the burr has been removed but, of course, we don't really know if that percentage is accurate. It's just a guess. We say the only way to remove this kind of burr is to grind it off, well that's our experience. If you see something here that we don't or if you just see it differently. Let's hear about it please. 

In closing, industrial operations should represent a real opportunity for professional sharpeners because most industrial users (and very often their edge suppliers) simply do not have the knowledge base that can found right here on the BESS Exchange. How large is this market? Look around the room you happen to be sitting in. It's difficult to pick out an object that wasn't sawn, sheared, sliced or cut in a factory before it became the product you see. Look in the pantry or the cupboard. Those sliced peaches didn't grow that way. We promise, there's a whole world out there beyond just kitchen and carry knives.
Reply
#2
Maybe not the messenger, but somebody should be.   Rolleyes
 
While it’s a little hard to tell exactly what is going on from those particular images, it is obvious that the edge is, at the very least, incompletely deburred and probably not sharpened evenly and completely.  It’s no wonder there is variation in the sharpness readings along the edge.  More scientifically, accurately and generously grandmotherly, I’d describe that edge as a mess.
 
Mr. EOU did not specify the specific cutting operation, but I would guess that type of blade would perform best with a polished edge, and that blade obviously is not.  Even if I were sharpening a kitchen knife and wanted a toothy edge, if I saw that under the microscope I’d resharpen and then commence basic deburring.
 
Even more interestingly, that blade almost looks used, rather than freshly sharpened.  I’m surprised that a blade that looks like that could pass QC.  It certainly wouldn’t on my watch.  It’s not surprising the industrial customer is dissatisfied with the performance of that blade.
 
Here is an image of a blade that I sharpened to a mirror finish.  While it is not perfect and there are still micro scratches on the bevel, to the unaided eye the bevel was a mirror and it was extremely sharp.  The difference between this edge and the industrial customer’s blade is obvious.
 
   
 
If the EOU images are representative of typical blades in the industrial world, I’d have to agree with Mr. EOU’s statement that, “…industrial operations should represent a real opportunity for professional sharpeners…”
Reply
#3
Mr EOU, when I spoke recently about learning something of significance about the burr, and how I thought it related to something said about "always being on the burr side", and Mr KG said something about the "base of the burr", this looks to be what I was talking about.

If you can see any sort of aberration, I mean ANYTHING that doesn't look like a perfect scratch pattern to The Edge Of The Edge, that's what I call "the base of the burr".

You're right, you can't get rid of the base of the burr without "grinding it off". The trick is to remove the base of the burr *without making a burr on the other side*.

There are two ways I do this. I make one pass on a 140 grit Atoma and examine with the 60x mini microscope. This is sharpening at the "speed of smell", and that's how I totally maximize tooth. The other is to Control the rate of abrasion with very fine (but very sharp) abrasive on a Kally with a leather belt. 

When I said that I don't think you can do that with a grinder, it's because y'all don't use compounds. Also, you can't slow the abrasion down to 20 SFPM, like honing by hand.

It takes Way more passes on a stone than one would think to eliminate Everything except a clean scratch pattern. When I said something like, "once you eliminate the base of the burr, there is no more burr", that's what I meant. The off-burr side has a perfect scratch pattern all the way to the EOTE. It has to. That's what makes the burr on the burr side. 

Now, here's why it doesn't work with a clean leather belt- you have no abrasion going on at all. Leather is too soft to affect steel in any meaningful way, other than to Slightly bend Very Thin steel. You can't remove anything. You can't abrade the steel. You need something harder than steel to do that.

That's what compounds are for. There are abrasive particles in the compound that are harder than steel, so they scratch some steel off. They cut into the steel, and leave a scratch pattern, even though it can be very fine.

That's why it's super quick and easy for me to remove the burr with a Kally and poly diamond compound, and that's why it's impossible with bare leather or a clean cotton buff. There will never be a scratch pattern, since there can't be any scratching going on.

Put some poly diamond particles on the leather, then run the burr side against the leather. You will get a scratch pattern all the way to the EOTE. You will remove the "base of the burr", or whatever you want to call that "shiny line" or "line of crud" as Mr Mike put it.

You don't have to put the compound on a belt, you can put it on a leather hone, like the ones I sent out, with 16 micron PDP compound on them. They deburr perfectly for me. 

I have no idea why that didn't work for everyone. When I was down in Mansfield with Mr Rupert, his hone worked on the S35VN of my Umnumzan, just as I reported when I got home. It's like it can't NOT work, if you understand what you're trying to accomplish.

My guess is since y'all aren't used to the speed of smell, you just didn't think anything was happening. If you were alternating sides of the blade before you had a scratch pattern all the way to TEOTE on the burr side, you were wasting half your time on the side that DID have a scratch pattern all the way to TEOTE.

Oh yeah, one more thing. I also said it can FEEL like you flipped the burr, without flipping the WHOLE burr. That is another trait of of not affecting the "base" of the burr. There is WAY more steel in the burr than you think.

With plain leather, it makes no difference if you're using the smooth side or the rough side, because the rough side is the same hardness as the smooth side, and neither side is hard enough to remove Any steel. At any rate, you will Never see a scratch pattern from leather.

No scratchy= no toothy= no sharpy.

Don't forget, the burr side is Not the same as the other side of the edge.  

If this doesn't make sense, and just makes you mad, please refer to the appropriate title of this thread. This is nothing but MHO at this time.
Reply
#4
I have no experience with industrial blades sharpening, nevertheless I see some similarity with sharpening plane irons. I do it on Tormek and the customers are satisfied.
   
A blade of 1.5" width requires careful alignment in the so called square edge jig. Before sharpening the stone has to be flat and parallel with the support bar on which the jig moves sideways. If necessary to stone surface has to be trued with guided diamond tip.

   
Setting the edge angle is not difficult, but more challenging is setting the (almost) same angle for honing the edge on the leather honing wheel. The blade is still in the jig and moves sideways guided by the support bar.
   
Following this simple Tormek protocol I usually do not have difficulties with burr removal, contrary to freehand honing case. The sharpening occurs towards the edge while the honing of course away from the edge.

The bevel has hollow shape, but it can be shown that it is not weaker compared to flat grind. Wink

Jan


Reply
#5
Thanks to Mr. EOU, today I've learnt of a new species of burrs created by "too much grinding force"; I don't think savvy sharpeners ever produce it, and the base of this burr should be somewhat different to what we've been talking about before this post - not a malleable band of foil, but rather a meaty and substantial base, rising from the bent edge apex.
I can only echo Grepper, that such burrs can't be just deburred as there is no sharpness hiding behind its base - the edge should be re-ground with less force.

Mark, yours is the best insight into the burr and its removal I've ever read anywhere. (no flatter meant)
http://knifeGrinders.com.au
Reply
#6
Thanks to everyone for chipping in on this thread. We're especially thankful at the opportunity to widen our own KG's view of the sharpening world. KG makes a good point "savvy sharpeners never produce this kind of burr". Less than savvy sharpeners do though and that's why we like to bring things like this to the Exchange. There's a lot of expertise and knowledge vested in the members of this Exchange and, with luck, a less experienced sharpener will stumble across this thread or one like it and a light will go on.  KG has made great progress in the Australian/New Zealand meat processing industry. Once he's gathered a little more data from his customers it will be very interesting to learn more precisely how they sharpen, the health and safety benefits, and what they expect from an edge.

No real difference between industrial edges and knife edges Jan other than the fact that the sharpest edge is not necessarily the best edge in the industrial arena. Probably isn't in the knife arena either but we can argue about that another time. Most of what is discussed here on the Exchange can be directly applied wherever edges are sharpened. In to the edge for grinding and away for burr removal makes a lot of sense. 

We've spent enough time with Mark R on the phone and in person to realize that he knows his stuff. Anytime we are able to spawn a healthy writing like the one posted here from Mark makes it a good day for us. 

We think that we would like to continue to put up edges that our industrial customers submit to us. Most often, we sell an industrial edge tester and only hear from the customer again when they reorder test media. Sometimes they need help though so, where we can, we'll bring the story behind those edges to the Exchange. It's unlikely that you'll learn anything about sharpening from these industrial guys but there might be something to be learned about the tremendous breadth of sharpened edges that are in use, world-wide, today.
Reply
#7
I very humbly accept the... frankly, unbelievably kind words.

I'm really happy to finally get those thoughts conveyed to Gentlemen with keen, open minds.

It is certainly my pleasure to be part of such an outstanding league of honorable peers.
Reply
#8
This topic reminds me of reading my philosophy text in college; I need quiet, undistracted time to read it slowly. Once I created that time (early morning, my family still asleep, just a cup of coffee for distraction), my time and effort was well rewarded.

I am finally realizing that an unexpected benefit of the time I have spend modifying my belt grinders has prepared my mind to absorb things like the topics discussed here. Your posts in this topic are making things focused which were blurry before. This sense of understanding is even more satisfying because it also brings a continued thirst for more understanding. That is a positive sense of curiosity rather than a discouragement from the size of the unknown.

I look forward to quiet early morning time over the holidays savoring bessex thoughts. Many thanks for sharing your thoughts.

Ken
Reply
#9
Mike, guys,
I know how such "scraper burr" forms, I've just had an aha moment:
this is a one-sided burr.

Burr like that is raised by repeated abrasion of one side of the blade;
or as an option grinding is done on both sides, but asymmetrically so that it covers the edge end on one side only.

As a result of platic deformation, the edge apex will bend on one side, and a thick burr will grow.
This burr will be several microns thick all the way from its base to the end.

Manufacturers sharpen these blades by overlapping grinding wheels, similar to Tru Hone - I bet the grinding wheels are not aligned.
http://knifeGrinders.com.au
Reply
#10
Thanks KG and everyone else who have provided support on this topic.  Good thoughts/suggestions and something to take up with the customer. We've sharpened a couple of blades at different sharpness levels (we hope correctly) and sent them to the customer. Hopefully, one will perform better/longer than the other and we'll be on the right path. The customer has purchased an ID75A edge sharpness testing system for their supplier so that will go a long way towards placing both on the same page.
Reply


Forum Jump:


Users browsing this thread: 1 Guest(s)