Monday, June 11, 2012

Sharp as a razor, part I

This week it has been raining. At best, completely clouded. I suppose this helps the garden. But I have been indoors a lot. I have sharpened a lot of tools; in fact I am currently making a gouge-sharpening jig. But that must wait. I am starting a series on sharpening. In the manner of all blogs, the threads get tangled. Bears get tangled up with axes, so to speak. So I have a new label or two for this thread.

All edge tools must be sharpened. If you neglect to do so, the tool will cut badly if at all. Worse, it will slip and possibly injure you. A dull tool is a menace. True even for kitchen knives. Now, on the market you will find many machines that you are urged to buy. But before you plunk down your cash for one of these things, I recommend learning to sharpen by hand. Japanese masters begin their day by sharpening all their tools. By hand, of course. It can be a Zen activity if approached in the right way. Let us start our Zen Journey.

We do need one bought-in item for this activity. A sharpening stone. There is a huge number of stones on the market: arkansas, ceramics, carborundum, diamonds, waterstones and no doubt Plutonium chromide by now. However, in my personal opinion there are only two. Diamond and Japanese waterstones. I use diamonds on the tools I make myself, to get a rough edge. I also use it on kitchen knives, which are stainless steel. After that, it's waterstone all the way, plus a leather strop. Every time I resharpen, it's waterstones. So what is a waterstone? You will find a picture of one in the Lee Valley catalog. The one I use is labeled "1000/4000 grit." So what's a grit? A measurement of average particle size in the stone. The larger the number the more particles per cubic whatsis in the stones, so the smaller the particles are. For practical purposes 1000 is medium and 4000 is fine.

Waterstones are used sopping wet. One stores them in a water-filled "pond." Some people will try to sell you one. Don't bother. Use a dollar store basin, or cut the bottom off a large plastic detergent bottle and use that. So we have a waterstone. We have a place to store it.

You have just bought a brand X chisel. Disappointed with it? Right. It ain't sharp. Now let's start sharpening. Look at the bevel on the chisel. You will see little scratches on it (unless you bought a really good chisel at a corresponding price). You chisel has been ground on a machine. But it hasn't been sharpened. Our objective is to get rid of the scratch marks. So we unlimber our Japanese waterstone.
Here you see the very same stone shown in the Lee Valley cite above, in a homemade holder. It is soaking wet. The 1000-grit (medium) side of the stone is up. Now, rock the chisel until the bevel is absolutely flat on the stone. Now all you do is press down on it and rub it back and forth. Use quite a lot of pressure, and whatever you do keep the bevel flat on the stone. If you go slow, this is easy. If you go fast it ain't. Go slow at first. You will see a blackish powder appearing. Good. This is called swarf. Means the stone is working. It is basically metal dust and some abrasive. Periodically you lift the chisel and wipe it off. Then you feel for the burr. It cannot be seen by the eye, but can be felt with the fingers. It is a slight irregularity on the back side of the edge, the side that is up in the picture. When you get the burr, you have gone far enough with that grit. Get rid of the burr by turning the chisel over so bevel is up. Lay back side flat on the stone and give it a couple of passes. You should not feel any burr after that.

Now turn the stone over, so 4000 grit side is up, and repeat. You know, back and forth, raise a burr, get rid of burr. When you are finished, strop it. This post has gone quite far enough, so I will defer stropping. All tools are done more or less the same way, but there are many innuendoes and tricks for different tools. Such as knives and gouges. Axes are a completey diferent animal. Get to them any time now.

At the end you may have some scratch marks in the middle of the bevel. This is acceptable. Reason is your tool was hollow-ground. But you should have no scratch marks at all at the ends of the bevel.

More (like the iceman) cometh later.

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