Thread: Why Pyramid?

This is an interesting thread. The pyramid has been a mystery to me for a long time. I think I understand it better after Lynn's explanation.

From Nenand's post you'll see that there is a science of sharpening. I scanned that thesis and it looks excellent. It may answer amny of my questions. It's my style to try to understand things, so when I got into honing I started researching and looking for an understanding of things, as well as experimenting. I still have a lot to learn, but I have learned some principles, and I'll discuss them below. When something is my theory or a guess, I'll say so.

There's a lot of black magic discussed here. from a scientific point of view Jeff comes closest and I agree with him on just about everything. He has a strong curiosity and a obviously a good basic understanding.

First of all, let's talk about striations or scratch lines. They're caused by the grits in an abrasive, which produce furrows that are usually at an agle to the edge. Since hey're on the bevel of the edge, where they meet the edge they produce a series of teeth (microserrations), which get smaller with finer grit. You always have them. A basic principal is that a sharper edge cuts with less effort. So, theoretically the edge should improve as you use finer abrasive, because the edge gets sharper. In other words, you want the finest edge you can get without making it so fine that it doesn't hold up and you need to hone all the time. Sharpness vs. durability is the traditional tradeoff in sharpening. All the usual principles DO aopply, but we have the luxury of being able to create very sharp edges because they will stand up to a beard.
It's been suggested that the teeth produced by a 4K hone are necessary for best for shaving. It seems to be based on the barber's manual discussing teeth in the edge. A barber's finishing hone is around 10K, so the teeth we're talking about are even finer than those produced by an 8K hone. Lynn tells us he finishes with a coticule, which he estimates at 12K. So, the edges he gets are even finer than traditional barber's edges. Frankly, I don't understand how a blade with coarse teeth could shave smoother than one with fine teeth. There's a lso the issue of comfort. The striations on the bevel will come int contact with the skin when you shave. Larger scratches make a rougher surface with more friction.

It's been suggested that the best edge is made up of large teeth with small ones between them. Assuming you hone with the finer hone without eliminating the 4K scratches entirley, you're simply dividing the ridge between 4K scratches into multiple ridges (say 3 if your'e usig a 12K stone). That gives you groups of 12K teeth separated by 4K scratches. Is that better than all 12K teeth?

That brings me to the pyramid. It's a good approach when you're first starting out because you have no idea what's going on, and if you can follow these steps and keep testing you'll eventually get where you want to be. I agree with Jeff that reverting to a coarser grit has to set you back, even if it's a little. When I hone, I don't go back to a coarser grit. I'll start and edge with a 1200 withe spine edges taped, if I need to remove a lot of material or create a new edge. Otherwise I'll start on the 4K. I come off the 4K when I pass the thumbnail test or when the edge looks nice an even. The 8k finishes the edge to look even under a microscope and to pass the thumb test. When I get no more improvement with the 8K I move on to the coticule. I stop the coticule when I get no more edge improvement. I don't know how many strokes I do on each abrasive. It's different with each razor, anyway.

I hope nothing I said leads anyone to think I need 4k teeth to shave. Thats not the case. I don't need .25, or .5 or even 1k either. But I think I may need teeth. And I like shaving with a razor thats not too sharp, its nice and fun and it feels good. What more is the point of all this stuff? I am curious if you can erase the teeth and not get a good shave. I don't know if I've done that or not, but I have honed for a long time and made a blade that didn't shave well, many times actually.

X, I followed all of your AAAAAAAA comments, save one, the AA"""AA""AA""" interspersed. I'm not sure how you could intersperse the striations like that or any other way.

ok, here's the link on the excellent file on knife sharpening, from the Iowa state university. I strongly suggest you all read it, you will know what you discuss about...

http://mse.iastate.edu/files/verhoeven/KnifeShExps.pdf


check this file, too... it's called: Metallurgy of Steel for Bladesmiths & Others
who Heat Treat and Forge Steel.

http://mse.iastate.edu/files/verhoeven/7-5.pdf

have fun,
Nenad

p.s. Science behind Damascus steel:

http://mse.iastate.edu/files/verhoev...earchsize2.pdf

Nenad,

I don't see anything in the links, but I'm looking forward to finally knowing what I'm talking about...

Originally Posted by AFDavis11

Nenad,

I don't see anything in the links, but I'm looking forward to finally knowing what I'm talking about...

LOL! Amen, brother, me too! It is a blast exploring these things...

Jeff

the links came up eventually, they take a while to load though...reading them might take a while though...

Originally Posted by AFDavis11

X, I followed all of your AAAAAAAA comments, save one, the AA"""AA""AA""" interspersed. I'm not sure how you could intersperse the striations like that or any other way.

They don't actually fit in together quite so neatly, but think of it in three dimensions, the deapth of the striations from the surface down. Again, it's impossible to get them even, but the various levels (which I'm sure are being created) can make the edge easier to cut with.

X

The pdf files are quite big, best move is to right-click them and select "Save (link) as"...

I didn't ment to offend any of you, I wanted to say that you will be able to see the razor's and knifes edges with best quality magnification at ~1000x, the very edge too, and read some usefull stuff about some knife sharpening systems...

Nenad

Originally Posted by xman

They don't actually fit in together quite so neatly, but think of it in three dimensions, the deapth of the striations from the surface down. Again, it's impossible to get them even, but the various levels (which I'm sure are being created) can make the edge easier to cut with.

What actually happens is that the space between striations or scratches is subdivided into a plateau with thinner scratch lines. So, if you went from 4K to 8K each plateau is divided in half. To me it looks like pairs of 8K striations with a 4K space between them. How do you think this would cut any better than a continuum of 8K striations?

If a hair is 3 thousandths of an inch in diameter, even at 4K you get about 12 teeth on it. THe idea witha razor is that finer teetch are thinner and cut better. It's not like a serrated edge where you slide the teeth along the length of the edge. In a razor that kind of sliding movement is slight. Mostly, the edge moves forward into the hair. Even then, I would think the finer teeth would cut better because the hair is engaged by more teeth for a given amount of sliding movement.

Excellent images in that document, and definitley a good read. The pictures lend to my original thoughts that a 4K would scratch up a nice 8K finish. However the edge required to best cut hairs in the facial enviorment may include the 4K groves. As we are not just cutting hairs, but also scraping away some skin (hopefully not too much) in a soapy medium. I guess there are a few factors to consider that may also affect the performance of an edge.
I may be wrong but will too sharp of an edge lend to razor burn? Or is that due to technique, like too much pressure or too steep of a shaving angle?

Emil