EDGE RETENTION/ROLLING PART II

[Mike Brubacher]

So what if when I went to college we had hitching posts in the campus parking lots instead of parking places? Parallel parking is still parallel parking. At my college we were talking about "our feelings" while Sigmund Freud was still in high school. 

I'm just trying to help shape a kinder, gentler and more sensitive Grepper.

[Jan]

Mike, because Sigmund Freud was born in my country which was at that time part of the Austrian Empire, I would like to be clear about the meaning of your sentence "At my college we were talking about "our feelings" while Sigmund Freud was still in high school". Thanks.

Jan

[Ken S]

Jan,

Very nice portrait of your countryman.

Mike, 

The store where I purchased both of my digital cameras had buggy parking. It was a village general store in the village of Walnut Creek, Ohio. It catered to the local Amish and Mennonite communities. In one corner, it was also a full service Nikon dealer. The owner was very knowledgeable in film and digital photography. He was very honest; I trusted his judgement completely. He also did clean up after the buggies, from high school until he retired. It was always a treat to see him.

Ken

[Mike Brubacher]

Yes Jan I see now the confusion that I've caused here. You are referring to the world famous Sigmund Schlomo Freud and I was referring to the much less famous Sigmund Clarence Freud (no known relation) of western Harvey County, Kansas. S.C. Freud was a  small dairy farmer who  never married and produced no offspring. It was rumored  that he spent hours in the milking parlor simply talking to his cows while he smoked cigars. Supposedly, he would be seated on a milking stool, taking notes, while the cows reclined on couches. It is fact that he had the highest producing milk herd in the county.

Ken you are referring to a region of Ohio where hardworking and devout Mennonites settled. That bunch doesn't mind cleaning up messes. I come from a region where a less ambitious branch ended up, their lassitude leading them to invent contraptions such as this one;

                                   

With those things cleared up perhaps we can soon return to which edges roll  a lot and which edges don't roll so much.

[grepper]

Mr. Bud,  "Did you all used to play football? Without helmets?"

How did you know???

[Mark Reich]

Heh heh!  Yes, I'm suffering like succotash.

I believe you probably do understand, Mr. Grepper, but just in case I'll try to explain something about "bevels", because it's not quite as intuitive as everyone would think.

Most blades have two bevels on each side of the blade. There is a "blade bevel" and an edge bevel The "blade bevel" makes the side of the blade taper from wide at the spine, to narrow at the edge. This makes the blade's profile. The profile can be hollow ground, flat ground or convex ground, but just for simplicity, let's say this taper goes all the way from spine to edge. Otherwise there is "Skandi grind" and "saber grind" too.

We aren't talking about the edge yet, just the grind that makes the blade taper from the wide spine to the narrow edge. That is one bevel, and it's the large one I'm calling the "blade bevel" for now. It is this "blade bevel" that is usually about 3-5 dps, but it can vary a lot.

Now we want to sharpen the edge of the blade, so we grind another small bevel on each side of the blade, and they meet at the apex of the edge. We can call that the edge bevel, and everyone knows what we're talking about, right?

We can use these terms to describe the difference of the blades on the whiteboard. Mike's blade doesn't taper from spine to edge, so his blades have a straight profile (not to be confused with a Flat Bevel). Mike's blades only have one bevel  per side (or less- the single bevels only have... a single bevel... on one side), which meet at the apex to form the edge. It would be easy to cal these "edge bevels".

Maybe it's easier to understand the doodle on the whiteboard now. The white triangle in the center is just a blade that has a flat ground profile. You can't see an edge bevel on the flat ground profile. The edge is still .015"thick, going to (or coming from) HT. The darkened area is Mike's straight profile blade, with 15 dps edge bevels. Mike's bevels meet to form an edge pre- heat treat.

I hope you can see on the whiteboard how little steel is left with a flat ground profile, compared to how much steel Mike's blade has left. All that extra steel behind the edge keeps it straight during HT.

So now that everyone is jiggy with that, please allow me to confuse everything.

Wouldn't it be so much easier if we could just say "primary bevel" and "secondary bevel"? Yes! Of course! All we have to do is agree which bevel is "primary" and which is "secondary"! 

So far, as long as there have been knives, the human race can not agree which bevel is more important. 

Some people think the big bevel should be the primary bevel. It is big, and you have to grind it before you grind the edge.... but wait. There are those (ridged Japanese knife folks) who say that the entire knife is there only to support the edge. In other words, the edge is most important, so the part that does the cutting is the primary reason to own a chunk of steel.

Then too, Mike's blade only has one bevel per side (per side is always a given, except when it's not, like chisels, and probably scissors, and other stuff). If a blade only has an edge bevel, how could it be secondary? What about blades that have a Micro-bevel?? 

It would have been much easier to describe the drawing using "primary" and "secondary", if we could agree which is which.  

So while not being very intuitive, most knifemakers agree that a knife Always has an edge, and the edge is primarily important for a knife most of the time.

Please forget "blade bevel". That isn't a real term like "blade profile", which is more commonly known as "secondary bevel".

Now let's see how much of that sticks...  

[Mike Brubacher]

That's what I was talking about. Thank you Mark!

[Ken S]

This is a situation where the scholarly sharpeners of the world would assemble behind closed doors. After arduous debate, the elected leader would reach into his (or her) pocket and pull out a coin. We know the rest........

Seriously, excellent and informative post, Mark.

Ken

[Bud]

Here's the way I see it. If you have a long sloping bevel at say 5 degrees and then a shorter bevel of say 15 degrees then the long bevel is primary and the short is secondary. If you have a short 15 degree bevel like Mike's test blades and then a very small bevel of 20 degrees I call the 15 degree bevel primary and the 20 degree micro bevel. I understand that someone or everyone could mix those up or reverse them and they'd still be correct. Its just how I think about it. It would be good if everyone was reading out of the same book though. I'd be willing to change how I look at things.

[Mark Reich]

Thank you, Gentlemen!

Mr Bud, it is hard to fault your logic, and you're right, "people could reverse them and they'd still be correct".

That's precisely the problem. People Do reverse them. More often than not even. I think part of it comes from the segment of the population that wants to be "deep thinkers". They're actually winning this one.

To be fair, the more you discuss bevels, the easier it becomes to recognize the edge as the primary bevel IMHO, but I don't appreciate people calling a micro-bevel the primary bevel, which happens often enough to cause problems. That's thinking a little too deeply for me, and probably Mr. Grepper too. 

"Nobody told me I'd have to think."