Tool Sharpening Basics

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But before you get to filing, let's look at your digging tool a second. Is it rusted? Not good. As MOTHER'S Dennis Burkholder puts it, "The only thing that'll ruin the edge on a tool faster than using it is abusing it. And nothing'll pit up an edge faster than rust." So scrape off as much rust as you can with steel wool, and from now on clean off this (and every) tool after you use it, and rub it lightly with oil to keep new rust from forming. This simple step will greatly extend the edges and lives of your tools.

Now for the real work. First, run your file around the top of the edge some, if need be, to smooth out any nicks in the blade (Fig. 1). Then consider: A shovel or spade is a single-beveled tool. It has only one sharp edge, which leads us to: Sharpening Axiom No. 1: Sharpen single-beveled tools ONLY on the beveled side(Fig. 2). You can ruin the cutting edge of the tool otherwise. In real life, you could probably rescue a rough tool like a shovel from the mistreatment of having both sides filed.

But do that to your scissors or prized pruners, and they'll be headed for the junk pile. So brace your spade or shovel well—this and, almost every sharpening job will go easier if you clamp your work with C-clamps or in a vise—and file it on the top, the beveled side. (Keep your forgers out of the way.) You can run your file up into the blade or down the blade, whichever's easier. Use a file that matches the contour of the blade: a flat one for that flat-faced spade and a half-round one for the curved shovel.

What kind of angle should you sharpen at? Ah, that takes us right to: Sharpening Axiom No. 2: In general, sharpen the bevel at the same angle that was already there. In other words, if you can tell what angle the manufacturer or prior sharpener used, follow it.

If you can't tell, move on to: Sharpening Axiom No. 3: Sharpening at a steep angle gives a more durable edge; sharpening at a low angle gives a sharper edge (Fig. 3). The thin edge produced by low angle sharpening will obviously be sharper than a wider edge, but it will be more brittle as well. Since we're honing a digging tool that's likely to strike roots or rocks, a tough edge is probably more important than a super sharp one, so sharpen your spade at a fairly—high angle say, one that puts a shine back only about 1/4 inch into the blade. Press the file hard on your forward stroke, going the full length of the sharpening tool (so you won't wear the file out in one spot). Your backstroke should be light, little more than the weight of the tool, to keep from breaking any file teeth.

And angle the file across the blade face as you push rather than going straight into the blade (Fig. 4). That'll help you sharpen the edge evenly. It may also help you run the file teeth at a more effective right angle to your work. (Does that sound cuckoo? Look at the lines of file teeth. If they run at an angle, working the file across can help run those teeth right into the work.) Sharpener Collier Davis dips his file in water frequently as he works, to wash off the shavings, and says that this lengthens the life and increases the bite of the tool. Eventually, though, any file will wear out. When yours doesn't work well anymore, and unclogging it with a wire brush won't fix it, replace it. Once you've run the file across the entire blade a while, you'll have created a shiny tapered edge. If you run a finger on the underside of the blade, from the inside out to the tip, you may be able to feel a slight burr (also called a wire or feather ) at the edge. That's the best sign that things are getting sharp.

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