|Finally done with side A
||[Dec. 16th, 2011|11:15 pm]
Back on the 10th, on Saturday, I boldly proclaimed "I've got the first side done." Even earlier, I'd claimed I was going to all the rest by hand, with no more powered machinery.|
On Sunday, I looked at the wheel in dismay. I had clam edge.
I looked at it under bright light, and saw all the places where the scratch pattern wasn't right, where there were still hollows and irregularities in the flats, how the edge was thicker on one side, and how the edge, while ground to the proper angle, transitioned abruptly to the angle of the rest of the bevel. By design there is nothing truly flat on this wheel, all the surfaces are curves. The curve from edge to the ridge where it meets the hub should be a graceful arc, meeting the other side in a very sharp parabola.
I tried to find an appropriate picture of a clam in cross section so I could point out why it's called "clam edge," but couldn't find a single good example. A clam edge is a flaw, but not a fatal one -- the traditional "primary bevel/secondary bevel" western knife edge geometry works just fine, and is perfectly appropriate for such a blade.
The edge bevel is set at about 12 degrees for at least 2mm all around on this wheel, but the flats are, well, almost flat. It is maybe 5 degrees once you get about half a centimeter in, with some truly horrible scratches, dips, ridges, and bulges in the transition. The eye makes it worse than it is, making it look like it gets thicker, then thinner, then thicker again, the changes in angles confusing the brain. In some places, though, clearly there was a dip in the surface -- the hard stone skips over those, and the scratch pattern is interrupted and different there.
So, on Sunday, I went back, and finally finished side A.
On Monday, the 12th, I again took a look at both sides. Side B, which I had already jokingly proclaimed to be 3x as hard as side A, turned out, indeed, to be at least that much worse. Due to some heavy scale and irregularities in the bevel, I'd had to grind deep, and in several places a test with the flattened kongo-do showed that the blade had a concave profile, almost a hollow grind, with only a bit near the edge and patch near the hub contacting the stone. The hub was too thick, the surface was too irregular, the edge was still too thick.
So, despite having thought I was done with it, I fired up the wet grinder again. I took a chunk off up at the hub, smoothed out the dips and irregularities, thinned down the edge, and then turned over the blade and tried to think like a master.
It wasn't done yet. There were still three dips, scratches from the earlier run with the grinder showing in the slight hollows, an aureola of lighter, darker scratches surrounding the shining depths. And I still had clam edge, more apparent now that I'd knocked off some of the clam edge on the opposite side.
So, for the last time, this time for sure, side A went back to the grinder. A bit around the hub just to flatten that out a bit, a lot near the edges. It's still too thick for about half the circumference, but that's doable by hand. Doing what took about an hour with the grinder instead of by hand probably saved me nearly 10 hours. Also, somehow the grinder has developed a leak. I'll deal with that later.
I removed the grind marks on side A, and decided I was finally done with it.
Tuesday I GM'd a steampunk RPG adventure I cam up with, a Girl Genius pastiche using slightly modified Feng Shui rules. My players tell me they enjoy it, so I think I'm doing a good job.
Wednesday, I took a look at side A, and tried to grind out the last of the three dips. The stone is definitely broken in, as I had to flatten it to get it to focus on the problem areas. To flatten or otherwise shape a stone, a different, special stone is used. Called uncreatively a flattening stone, it's a hunk of aluminum oxide coated in titanium oxide bonded together and deeply slotted. You rub the out-of-true stone against it to wear off the high areas, and you can pretty quickly achieve a nearly perfectly flat surface on even the coarsest stones. In this case, I wanted it flatter, but not perfectly flat, and spent about a quarter hour on getting the profile I wanted.
I finally got rid of the last of the evil bevel dips, to the point where they just weren't visible anymore. I knocked down some more of the clam edge, too, going all the way around and blending the surface from edge to bevel, smoothing it out, and thinning out the edge some more. In some spots, perhaps too thin.
At this stage of the game, doing heavy removal still, I'm gripping the blade pretty hard, pressing down on the stone, and using considerable force, with wet fingers on a slick steel surface coated in a slurry of wet clay. The blade cannot yet be at full sharpness, so I took off just a bit of edge, not enough to be visible, but enough to give me a fraction of a millimeter, enough to not have to worry about cutting, or loosing a finger due to slip. So to sharpen the blade, first I had to dull it. A few bone-quivering scratches later, and it was done. Knock off the burr and continue.
I make some real progress on the B side, though I'm nowhere near finished. It's working a lot better now, and I soon have a good chunk of the blade with a nice, even scratch pattern.
And, at last I'm done with side A.
Thursday. I break out the 10x loupe, and take a good look at some fuzzy patches on side A. Scratches going the wrong way, where those dips had been. I take them off, and work on the clam edge, much less prominent now. Finished side A, finally. This time for sure.
Side B got a lot of attention, and I worked it down enough that there are just patches of wrong scratches instead of large, connected fields.
Friday. No need for the loupe, it's clear, I still have clam edge on side A. I work on it a while, try to remove the bulge while leaving enough meat to support the edge, try to flatten the curve without making it too flat.
I did that once, on my first tanto -- polished the edge so thin and sharp and flat that it literately started spontaneously cracking off pieces of the edge. Too hard, as I used 1095 and didn't temper enough, and too thin, and way too sharp (it would cut a piece of typing paper dropped on it's edge for a good half-inch, and you could slice a floating piece of paper from top to bottom with a single stroke). My first hamon, I was proud of it, and I still have it around in my collection of failed knives.
You learn more from your failures, afer all, than your successes.
Side B got some more love, but there's lots more to go.
And, at last, I'm done with side A. Except, of course, I'm not. The eyes of my inner master tell me I still have clam edge.
One last note, as I count my strokes, I realized I could make an approximation of how many strokes it will take to do this base polish. By my estimate, it takes about 200 strokes of the coarse stone to get a 10 degree section of blade foundation polished adequately. 2*360/10*100=14,400 strokes, at about 1/second, we're talking 4 hours of just polishing, and probably twice that time doing related tasks.
(I tapped her, just to hear her song. She cried instead. I'm not done yet, not by the sound of her. I can't be done until she sings without pain.)